X-Git-Url: https://git.madduck.net/etc/vim.git/blobdiff_plain/e1e89091d1de878c98e2d2b0cefd81cc75e7a128..65c52a655fd67480a2017a79c99094039dcaffa3:/black.py?ds=inline diff --git a/black.py b/black.py index 7ae2627..6bb29fe 100644 --- a/black.py +++ b/black.py @@ -1,17 +1,35 @@ #!/usr/bin/env python3 + import asyncio from asyncio.base_events import BaseEventLoop from concurrent.futures import Executor, ProcessPoolExecutor -from functools import partial +from enum import Enum +from functools import partial, wraps import keyword +import logging +from multiprocessing import Manager import os from pathlib import Path import tokenize +import signal +import sys from typing import ( - Dict, Generic, Iterable, Iterator, List, Optional, Set, Tuple, TypeVar, Union + Any, + Callable, + Dict, + Generic, + Iterable, + Iterator, + List, + Optional, + Set, + Tuple, + Type, + TypeVar, + Union, ) -from attr import attrib, dataclass, Factory +from attr import dataclass, Factory import click # lib2to3 fork @@ -20,7 +38,7 @@ from blib2to3 import pygram, pytree from blib2to3.pgen2 import driver, token from blib2to3.pgen2.parse import ParseError -__version__ = "18.3a1" +__version__ = "18.4a0" DEFAULT_LINE_LENGTH = 88 # types syms = pygram.python_symbols @@ -30,44 +48,104 @@ Depth = int NodeType = int LeafID = int Priority = int +Index = int LN = Union[Leaf, Node] +SplitFunc = Callable[["Line", bool], Iterator["Line"]] out = partial(click.secho, bold=True, err=True) -err = partial(click.secho, fg='red', err=True) +err = partial(click.secho, fg="red", err=True) class NothingChanged(UserWarning): - """Raised by `format_file` when the reformatted code is the same as source.""" + """Raised by :func:`format_file` when reformatted code is the same as source.""" class CannotSplit(Exception): """A readable split that fits the allotted line length is impossible. - Raised by `left_hand_split()` and `right_hand_split()`. + Raised by :func:`left_hand_split`, :func:`right_hand_split`, and + :func:`delimiter_split`. + """ + + +class FormatError(Exception): + """Base exception for `# fmt: on` and `# fmt: off` handling. + + It holds the number of bytes of the prefix consumed before the format + control comment appeared. """ + def __init__(self, consumed: int) -> None: + super().__init__(consumed) + self.consumed = consumed + + def trim_prefix(self, leaf: Leaf) -> None: + leaf.prefix = leaf.prefix[self.consumed:] + + def leaf_from_consumed(self, leaf: Leaf) -> Leaf: + """Returns a new Leaf from the consumed part of the prefix.""" + unformatted_prefix = leaf.prefix[:self.consumed] + return Leaf(token.NEWLINE, unformatted_prefix) + + +class FormatOn(FormatError): + """Found a comment like `# fmt: on` in the file.""" + + +class FormatOff(FormatError): + """Found a comment like `# fmt: off` in the file.""" + + +class WriteBack(Enum): + NO = 0 + YES = 1 + DIFF = 2 + @click.command() @click.option( - '-l', - '--line-length', + "-l", + "--line-length", type=int, default=DEFAULT_LINE_LENGTH, - help='How many character per line to allow.', + help="How many character per line to allow.", show_default=True, ) @click.option( - '--fast/--safe', + "--check", + is_flag=True, + help=( + "Don't write the files back, just return the status. Return code 0 " + "means nothing would change. Return code 1 means some files would be " + "reformatted. Return code 123 means there was an internal error." + ), +) +@click.option( + "--diff", + is_flag=True, + help="Don't write the files back, just output a diff for each file on stdout.", +) +@click.option( + "--fast/--safe", is_flag=True, - help='If --fast given, skip temporary sanity checks. [default: --safe]', + help="If --fast given, skip temporary sanity checks. [default: --safe]", ) @click.version_option(version=__version__) @click.argument( - 'src', + "src", nargs=-1, - type=click.Path(exists=True, file_okay=True, dir_okay=True, readable=True), + type=click.Path( + exists=True, file_okay=True, dir_okay=True, readable=True, allow_dash=True + ), ) @click.pass_context -def main(ctx: click.Context, line_length: int, fast: bool, src: List[str]) -> None: +def main( + ctx: click.Context, + line_length: int, + check: bool, + diff: bool, + fast: bool, + src: List[str], +) -> None: """The uncompromising code formatter.""" sources: List[Path] = [] for s in src: @@ -77,15 +155,35 @@ def main(ctx: click.Context, line_length: int, fast: bool, src: List[str]) -> No elif p.is_file(): # if a file was explicitly given, we don't care about its extension sources.append(p) + elif s == "-": + sources.append(Path("-")) else: - err(f'invalid path: {s}') + err(f"invalid path: {s}") + if check and diff: + exc = click.ClickException("Options --check and --diff are mutually exclusive") + exc.exit_code = 2 + raise exc + + if check: + write_back = WriteBack.NO + elif diff: + write_back = WriteBack.DIFF + else: + write_back = WriteBack.YES if len(sources) == 0: ctx.exit(0) elif len(sources) == 1: p = sources[0] - report = Report() + report = Report(check=check) try: - changed = format_file_in_place(p, line_length=line_length, fast=fast) + if not p.is_file() and str(p) == "-": + changed = format_stdin_to_stdout( + line_length=line_length, fast=fast, write_back=write_back + ) + else: + changed = format_file_in_place( + p, line_length=line_length, fast=fast, write_back=write_back + ) report.done(p, changed) except Exception as exc: report.failed(p, str(exc)) @@ -96,83 +194,163 @@ def main(ctx: click.Context, line_length: int, fast: bool, src: List[str]) -> No return_code = 1 try: return_code = loop.run_until_complete( - schedule_formatting(sources, line_length, fast, loop, executor) + schedule_formatting( + sources, line_length, write_back, fast, loop, executor + ) ) finally: - loop.close() + shutdown(loop) ctx.exit(return_code) async def schedule_formatting( sources: List[Path], line_length: int, + write_back: WriteBack, fast: bool, loop: BaseEventLoop, executor: Executor, ) -> int: + """Run formatting of `sources` in parallel using the provided `executor`. + + (Use ProcessPoolExecutors for actual parallelism.) + + `line_length`, `write_back`, and `fast` options are passed to + :func:`format_file_in_place`. + """ + lock = None + if write_back == WriteBack.DIFF: + # For diff output, we need locks to ensure we don't interleave output + # from different processes. + manager = Manager() + lock = manager.Lock() tasks = { src: loop.run_in_executor( - executor, format_file_in_place, src, line_length, fast + executor, format_file_in_place, src, line_length, fast, write_back, lock ) for src in sources } + _task_values = list(tasks.values()) + loop.add_signal_handler(signal.SIGINT, cancel, _task_values) + loop.add_signal_handler(signal.SIGTERM, cancel, _task_values) await asyncio.wait(tasks.values()) cancelled = [] - report = Report() + report = Report(check=not write_back) for src, task in tasks.items(): if not task.done(): - report.failed(src, 'timed out, cancelling') + report.failed(src, "timed out, cancelling") task.cancel() cancelled.append(task) + elif task.cancelled(): + cancelled.append(task) elif task.exception(): report.failed(src, str(task.exception())) else: report.done(src, task.result()) if cancelled: - await asyncio.wait(cancelled, timeout=2) - out('All done! ✨ 🍰 ✨') + await asyncio.gather(*cancelled, loop=loop, return_exceptions=True) + else: + out("All done! ✨ 🍰 ✨") click.echo(str(report)) return report.return_code -def format_file_in_place(src: Path, line_length: int, fast: bool) -> bool: - """Format the file and rewrite if changed. Return True if changed.""" +def format_file_in_place( + src: Path, + line_length: int, + fast: bool, + write_back: WriteBack = WriteBack.NO, + lock: Any = None, # multiprocessing.Manager().Lock() is some crazy proxy +) -> bool: + """Format file under `src` path. Return True if changed. + + If `write_back` is True, write reformatted code back to stdout. + `line_length` and `fast` options are passed to :func:`format_file_contents`. + """ + with tokenize.open(src) as src_buffer: + src_contents = src_buffer.read() try: - contents, encoding = format_file(src, line_length=line_length, fast=fast) + dst_contents = format_file_contents( + src_contents, line_length=line_length, fast=fast + ) except NothingChanged: return False - with open(src, "w", encoding=encoding) as f: - f.write(contents) + if write_back == write_back.YES: + with open(src, "w", encoding=src_buffer.encoding) as f: + f.write(dst_contents) + elif write_back == write_back.DIFF: + src_name = f"{src.name} (original)" + dst_name = f"{src.name} (formatted)" + diff_contents = diff(src_contents, dst_contents, src_name, dst_name) + if lock: + lock.acquire() + try: + sys.stdout.write(diff_contents) + finally: + if lock: + lock.release() return True -def format_file( - src: Path, line_length: int, fast: bool -) -> Tuple[FileContent, Encoding]: - """Reformats a file and returns its contents and encoding.""" - with tokenize.open(src) as src_buffer: - src_contents = src_buffer.read() - if src_contents.strip() == '': - raise NothingChanged(src) +def format_stdin_to_stdout( + line_length: int, fast: bool, write_back: WriteBack = WriteBack.NO +) -> bool: + """Format file on stdin. Return True if changed. + + If `write_back` is True, write reformatted code back to stdout. + `line_length` and `fast` arguments are passed to :func:`format_file_contents`. + """ + src = sys.stdin.read() + try: + dst = format_file_contents(src, line_length=line_length, fast=fast) + return True + + except NothingChanged: + dst = src + return False + + finally: + if write_back == WriteBack.YES: + sys.stdout.write(dst) + elif write_back == WriteBack.DIFF: + src_name = " (original)" + dst_name = " (formatted)" + sys.stdout.write(diff(src, dst, src_name, dst_name)) + + +def format_file_contents( + src_contents: str, line_length: int, fast: bool +) -> FileContent: + """Reformat contents a file and return new contents. + + If `fast` is False, additionally confirm that the reformatted code is + valid by calling :func:`assert_equivalent` and :func:`assert_stable` on it. + `line_length` is passed to :func:`format_str`. + """ + if src_contents.strip() == "": + raise NothingChanged dst_contents = format_str(src_contents, line_length=line_length) if src_contents == dst_contents: - raise NothingChanged(src) + raise NothingChanged if not fast: assert_equivalent(src_contents, dst_contents) assert_stable(src_contents, dst_contents, line_length=line_length) - return dst_contents, src_buffer.encoding + return dst_contents def format_str(src_contents: str, line_length: int) -> FileContent: - """Reformats a string and returns new contents.""" + """Reformat a string and return new contents. + + `line_length` determines how many characters per line are allowed. + """ src_node = lib2to3_parse(src_contents) dst_contents = "" - comments: List[Line] = [] lines = LineGenerator() elt = EmptyLineTracker() + py36 = is_python36(src_node) empty_line = Line() after = 0 for current_line in lines.visit(src_node): @@ -181,36 +359,41 @@ def format_str(src_contents: str, line_length: int) -> FileContent: before, after = elt.maybe_empty_lines(current_line) for _ in range(before): dst_contents += str(empty_line) - if not current_line.is_comment: - for comment in comments: - dst_contents += str(comment) - comments = [] - for line in split_line(current_line, line_length=line_length): - dst_contents += str(line) - else: - comments.append(current_line) - for comment in comments: - dst_contents += str(comment) + for line in split_line(current_line, line_length=line_length, py36=py36): + dst_contents += str(line) return dst_contents +GRAMMARS = [ + pygram.python_grammar_no_print_statement_no_exec_statement, + pygram.python_grammar_no_print_statement, + pygram.python_grammar_no_exec_statement, + pygram.python_grammar, +] + + def lib2to3_parse(src_txt: str) -> Node: """Given a string with source, return the lib2to3 Node.""" grammar = pygram.python_grammar_no_print_statement - drv = driver.Driver(grammar, pytree.convert) - if src_txt[-1] != '\n': - nl = '\r\n' if '\r\n' in src_txt[:1024] else '\n' + if src_txt[-1] != "\n": + nl = "\r\n" if "\r\n" in src_txt[:1024] else "\n" src_txt += nl - try: - result = drv.parse_string(src_txt, True) - except ParseError as pe: - lineno, column = pe.context[1] - lines = src_txt.splitlines() + for grammar in GRAMMARS: + drv = driver.Driver(grammar, pytree.convert) try: - faulty_line = lines[lineno - 1] - except IndexError: - faulty_line = "" - raise ValueError(f"Cannot parse: {lineno}:{column}: {faulty_line}") from None + result = drv.parse_string(src_txt, True) + break + + except ParseError as pe: + lineno, column = pe.context[1] + lines = src_txt.splitlines() + try: + faulty_line = lines[lineno - 1] + except IndexError: + faulty_line = "" + exc = ValueError(f"Cannot parse: {lineno}:{column}: {faulty_line}") + else: + raise exc from None if isinstance(result, Leaf): result = Node(syms.file_input, [result]) @@ -223,20 +406,30 @@ def lib2to3_unparse(node: Node) -> str: return code -T = TypeVar('T') +T = TypeVar("T") class Visitor(Generic[T]): - """Basic lib2to3 visitor that yields things on visiting.""" + """Basic lib2to3 visitor that yields things of type `T` on `visit()`.""" def visit(self, node: LN) -> Iterator[T]: + """Main method to visit `node` and its children. + + It tries to find a `visit_*()` method for the given `node.type`, like + `visit_simple_stmt` for Node objects or `visit_INDENT` for Leaf objects. + If no dedicated `visit_*()` method is found, chooses `visit_default()` + instead. + + Then yields objects of type `T` from the selected visitor. + """ if node.type < 256: name = token.tok_name[node.type] else: name = type_repr(node.type) - yield from getattr(self, f'visit_{name}', self.visit_default)(node) + yield from getattr(self, f"visit_{name}", self.visit_default)(node) def visit_default(self, node: LN) -> Iterator[T]: + """Default `visit_*()` implementation. Recurses to children of `node`.""" if isinstance(node, Node): for child in node.children: yield from self.visit(child) @@ -244,32 +437,41 @@ class Visitor(Generic[T]): @dataclass class DebugVisitor(Visitor[T]): - tree_depth: int = attrib(default=0) + tree_depth: int = 0 def visit_default(self, node: LN) -> Iterator[T]: - indent = ' ' * (2 * self.tree_depth) + indent = " " * (2 * self.tree_depth) if isinstance(node, Node): _type = type_repr(node.type) - out(f'{indent}{_type}', fg='yellow') + out(f"{indent}{_type}", fg="yellow") self.tree_depth += 1 for child in node.children: yield from self.visit(child) self.tree_depth -= 1 - out(f'{indent}/{_type}', fg='yellow', bold=False) + out(f"{indent}/{_type}", fg="yellow", bold=False) else: _type = token.tok_name.get(node.type, str(node.type)) - out(f'{indent}{_type}', fg='blue', nl=False) + out(f"{indent}{_type}", fg="blue", nl=False) if node.prefix: # We don't have to handle prefixes for `Node` objects since # that delegates to the first child anyway. - out(f' {node.prefix!r}', fg='green', bold=False, nl=False) - out(f' {node.value!r}', fg='blue', bold=False) + out(f" {node.prefix!r}", fg="green", bold=False, nl=False) + out(f" {node.value!r}", fg="blue", bold=False) + + @classmethod + def show(cls, code: str) -> None: + """Pretty-print the lib2to3 AST of a given string of `code`. + + Convenience method for debugging. + """ + v: DebugVisitor[None] = DebugVisitor() + list(v.visit(lib2to3_parse(code))) KEYWORDS = set(keyword.kwlist) WHITESPACE = {token.DEDENT, token.INDENT, token.NEWLINE} -FLOW_CONTROL = {'return', 'raise', 'break', 'continue'} +FLOW_CONTROL = {"return", "raise", "break", "continue"} STATEMENT = { syms.if_stmt, syms.while_stmt, @@ -281,7 +483,7 @@ STATEMENT = { syms.classdef, } STANDALONE_COMMENT = 153 -LOGIC_OPERATORS = {'and', 'or'} +LOGIC_OPERATORS = {"and", "or"} COMPARATORS = { token.LESS, token.GREATER, @@ -299,11 +501,13 @@ MATH_OPERATORS = { token.AMPER, token.PERCENT, token.CIRCUMFLEX, + token.TILDE, token.LEFTSHIFT, token.RIGHTSHIFT, token.DOUBLESTAR, token.DOUBLESLASH, } +VARARGS = {token.STAR, token.DOUBLESTAR} COMPREHENSION_PRIORITY = 20 COMMA_PRIORITY = 10 LOGIC_PRIORITY = 5 @@ -314,52 +518,54 @@ MATH_PRIORITY = 1 @dataclass class BracketTracker: - depth: int = attrib(default=0) - bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = attrib(default=Factory(dict)) - delimiters: Dict[LeafID, Priority] = attrib(default=Factory(dict)) - previous: Optional[Leaf] = attrib(default=None) + """Keeps track of brackets on a line.""" + + depth: int = 0 + bracket_match: Dict[Tuple[Depth, NodeType], Leaf] = Factory(dict) + delimiters: Dict[LeafID, Priority] = Factory(dict) + previous: Optional[Leaf] = None def mark(self, leaf: Leaf) -> None: + """Mark `leaf` with bracket-related metadata. Keep track of delimiters. + + All leaves receive an int `bracket_depth` field that stores how deep + within brackets a given leaf is. 0 means there are no enclosing brackets + that started on this line. + + If a leaf is itself a closing bracket, it receives an `opening_bracket` + field that it forms a pair with. This is a one-directional link to + avoid reference cycles. + + If a leaf is a delimiter (a token on which Black can split the line if + needed) and it's on depth 0, its `id()` is stored in the tracker's + `delimiters` field. + """ if leaf.type == token.COMMENT: return if leaf.type in CLOSING_BRACKETS: self.depth -= 1 opening_bracket = self.bracket_match.pop((self.depth, leaf.type)) - leaf.opening_bracket = opening_bracket # type: ignore - leaf.bracket_depth = self.depth # type: ignore + leaf.opening_bracket = opening_bracket + leaf.bracket_depth = self.depth if self.depth == 0: - delim = is_delimiter(leaf) - if delim: - self.delimiters[id(leaf)] = delim - elif self.previous is not None: - if leaf.type == token.STRING and self.previous.type == token.STRING: - self.delimiters[id(self.previous)] = STRING_PRIORITY - elif ( - leaf.type == token.NAME and - leaf.value == 'for' and - leaf.parent and - leaf.parent.type in {syms.comp_for, syms.old_comp_for} - ): - self.delimiters[id(self.previous)] = COMPREHENSION_PRIORITY - elif ( - leaf.type == token.NAME and - leaf.value == 'if' and - leaf.parent and - leaf.parent.type in {syms.comp_if, syms.old_comp_if} - ): - self.delimiters[id(self.previous)] = COMPREHENSION_PRIORITY + after_delim = is_split_after_delimiter(leaf, self.previous) + before_delim = is_split_before_delimiter(leaf, self.previous) + if after_delim > before_delim: + self.delimiters[id(leaf)] = after_delim + elif before_delim > after_delim and self.previous is not None: + self.delimiters[id(self.previous)] = before_delim if leaf.type in OPENING_BRACKETS: self.bracket_match[self.depth, BRACKET[leaf.type]] = leaf self.depth += 1 self.previous = leaf def any_open_brackets(self) -> bool: - """Returns True if there is an yet unmatched open bracket on the line.""" + """Return True if there is an yet unmatched open bracket on the line.""" return bool(self.bracket_match) - def max_priority(self, exclude: Iterable[LeafID] = ()) -> int: - """Returns the highest priority of a delimiter found on the line. + def max_delimiter_priority(self, exclude: Iterable[LeafID] = ()) -> int: + """Return the highest priority of a delimiter found on the line. Values are consistent with what `is_delimiter()` returns. """ @@ -368,13 +574,26 @@ class BracketTracker: @dataclass class Line: - depth: int = attrib(default=0) - leaves: List[Leaf] = attrib(default=Factory(list)) - comments: Dict[LeafID, Leaf] = attrib(default=Factory(dict)) - bracket_tracker: BracketTracker = attrib(default=Factory(BracketTracker)) - inside_brackets: bool = attrib(default=False) + """Holds leaves and comments. Can be printed with `str(line)`.""" + + depth: int = 0 + leaves: List[Leaf] = Factory(list) + comments: List[Tuple[Index, Leaf]] = Factory(list) + bracket_tracker: BracketTracker = Factory(BracketTracker) + inside_brackets: bool = False + has_for: bool = False + _for_loop_variable: bool = False def append(self, leaf: Leaf, preformatted: bool = False) -> None: + """Add a new `leaf` to the end of the line. + + Unless `preformatted` is True, the `leaf` will receive a new consistent + whitespace prefix and metadata applied by :class:`BracketTracker`. + Trailing commas are maybe removed, unpacked for loop variables are + demoted from being delimiters. + + Inline comments are put aside. + """ has_value = leaf.value.strip() if not has_value: return @@ -384,37 +603,58 @@ class Line: # imports, for which we only preserve newlines. leaf.prefix += whitespace(leaf) if self.inside_brackets or not preformatted: + self.maybe_decrement_after_for_loop_variable(leaf) self.bracket_tracker.mark(leaf) self.maybe_remove_trailing_comma(leaf) - if self.maybe_adapt_standalone_comment(leaf): - return + self.maybe_increment_for_loop_variable(leaf) if not self.append_comment(leaf): self.leaves.append(leaf) + def append_safe(self, leaf: Leaf, preformatted: bool = False) -> None: + """Like :func:`append()` but disallow invalid standalone comment structure. + + Raises ValueError when any `leaf` is appended after a standalone comment + or when a standalone comment is not the first leaf on the line. + """ + if self.bracket_tracker.depth == 0: + if self.is_comment: + raise ValueError("cannot append to standalone comments") + + if self.leaves and leaf.type == STANDALONE_COMMENT: + raise ValueError( + "cannot append standalone comments to a populated line" + ) + + self.append(leaf, preformatted=preformatted) + @property def is_comment(self) -> bool: - return bool(self) and self.leaves[0].type == STANDALONE_COMMENT + """Is this line a standalone comment?""" + return len(self.leaves) == 1 and self.leaves[0].type == STANDALONE_COMMENT @property def is_decorator(self) -> bool: + """Is this line a decorator?""" return bool(self) and self.leaves[0].type == token.AT @property def is_import(self) -> bool: + """Is this an import line?""" return bool(self) and is_import(self.leaves[0]) @property def is_class(self) -> bool: + """Is this line a class definition?""" return ( - bool(self) and - self.leaves[0].type == token.NAME and - self.leaves[0].value == 'class' + bool(self) + and self.leaves[0].type == token.NAME + and self.leaves[0].value == "class" ) @property def is_def(self) -> bool: - """Also returns True for async defs.""" + """Is this a function definition? (Also returns True for async defs.)""" try: first_leaf = self.leaves[0] except IndexError: @@ -425,50 +665,70 @@ class Line: except IndexError: second_leaf = None return ( - (first_leaf.type == token.NAME and first_leaf.value == 'def') or - ( - first_leaf.type == token.NAME and - first_leaf.value == 'async' and - second_leaf is not None and - second_leaf.type == token.NAME and - second_leaf.value == 'def' + (first_leaf.type == token.NAME and first_leaf.value == "def") + or ( + first_leaf.type == token.ASYNC + and second_leaf is not None + and second_leaf.type == token.NAME + and second_leaf.value == "def" ) ) @property def is_flow_control(self) -> bool: + """Is this line a flow control statement? + + Those are `return`, `raise`, `break`, and `continue`. + """ return ( - bool(self) and - self.leaves[0].type == token.NAME and - self.leaves[0].value in FLOW_CONTROL + bool(self) + and self.leaves[0].type == token.NAME + and self.leaves[0].value in FLOW_CONTROL ) @property def is_yield(self) -> bool: + """Is this line a yield statement?""" return ( - bool(self) and - self.leaves[0].type == token.NAME and - self.leaves[0].value == 'yield' + bool(self) + and self.leaves[0].type == token.NAME + and self.leaves[0].value == "yield" ) + @property + def contains_standalone_comments(self) -> bool: + """If so, needs to be split before emitting.""" + for leaf in self.leaves: + if leaf.type == STANDALONE_COMMENT: + return True + + return False + def maybe_remove_trailing_comma(self, closing: Leaf) -> bool: + """Remove trailing comma if there is one and it's safe.""" if not ( - self.leaves and - self.leaves[-1].type == token.COMMA and - closing.type in CLOSING_BRACKETS + self.leaves + and self.leaves[-1].type == token.COMMA + and closing.type in CLOSING_BRACKETS ): return False - if closing.type == token.RSQB or closing.type == token.RBRACE: - self.leaves.pop() + if closing.type == token.RBRACE: + self.remove_trailing_comma() return True + if closing.type == token.RSQB: + comma = self.leaves[-1] + if comma.parent and comma.parent.type == syms.listmaker: + self.remove_trailing_comma() + return True + # For parens let's check if it's safe to remove the comma. If the # trailing one is the only one, we might mistakenly change a tuple # into a different type by removing the comma. - depth = closing.bracket_depth + 1 # type: ignore + depth = closing.bracket_depth + 1 commas = 0 - opening = closing.opening_bracket # type: ignore + opening = closing.opening_bracket for _opening_index, leaf in enumerate(self.leaves): if leaf is opening: break @@ -480,107 +740,200 @@ class Line: if leaf is closing: break - bracket_depth = leaf.bracket_depth # type: ignore + bracket_depth = leaf.bracket_depth if bracket_depth == depth and leaf.type == token.COMMA: commas += 1 + if leaf.parent and leaf.parent.type == syms.arglist: + commas += 1 + break + if commas > 1: - self.leaves.pop() + self.remove_trailing_comma() return True return False - def maybe_adapt_standalone_comment(self, comment: Leaf) -> bool: - """Hack a standalone comment to act as a trailing comment for line splitting. - - If this line has brackets and a standalone `comment`, we need to adapt - it to be able to still reformat the line. + def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool: + """In a for loop, or comprehension, the variables are often unpacks. - This is not perfect, the line to which the standalone comment gets - appended will appear "too long" when splitting. + To avoid splitting on the comma in this situation, increase the depth of + tokens between `for` and `in`. """ - if not ( - comment.type == STANDALONE_COMMENT and - self.bracket_tracker.any_open_brackets() - ): - return False + if leaf.type == token.NAME and leaf.value == "for": + self.has_for = True + self.bracket_tracker.depth += 1 + self._for_loop_variable = True + return True + + return False - comment.type = token.COMMENT - comment.prefix = '\n' + ' ' * (self.depth + 1) - return self.append_comment(comment) + def maybe_decrement_after_for_loop_variable(self, leaf: Leaf) -> bool: + """See `maybe_increment_for_loop_variable` above for explanation.""" + if self._for_loop_variable and leaf.type == token.NAME and leaf.value == "in": + self.bracket_tracker.depth -= 1 + self._for_loop_variable = False + return True + + return False def append_comment(self, comment: Leaf) -> bool: + """Add an inline or standalone comment to the line.""" + if ( + comment.type == STANDALONE_COMMENT + and self.bracket_tracker.any_open_brackets() + ): + comment.prefix = "" + return False + if comment.type != token.COMMENT: return False - try: - after = id(self.last_non_delimiter()) - except LookupError: + after = len(self.leaves) - 1 + if after == -1: comment.type = STANDALONE_COMMENT - comment.prefix = '' + comment.prefix = "" return False else: - if after in self.comments: - self.comments[after].value += str(comment) - else: - self.comments[after] = comment + self.comments.append((after, comment)) return True - def last_non_delimiter(self) -> Leaf: - for i in range(len(self.leaves)): - last = self.leaves[-i - 1] - if not is_delimiter(last): - return last + def comments_after(self, leaf: Leaf) -> Iterator[Leaf]: + """Generate comments that should appear directly after `leaf`.""" + for _leaf_index, _leaf in enumerate(self.leaves): + if leaf is _leaf: + break + + else: + return + + for index, comment_after in self.comments: + if _leaf_index == index: + yield comment_after - raise LookupError("No non-delimiters found") + def remove_trailing_comma(self) -> None: + """Remove the trailing comma and moves the comments attached to it.""" + comma_index = len(self.leaves) - 1 + for i in range(len(self.comments)): + comment_index, comment = self.comments[i] + if comment_index == comma_index: + self.comments[i] = (comma_index - 1, comment) + self.leaves.pop() def __str__(self) -> str: + """Render the line.""" if not self: - return '\n' + return "\n" - indent = ' ' * self.depth + indent = " " * self.depth leaves = iter(self.leaves) first = next(leaves) - res = f'{first.prefix}{indent}{first.value}' + res = f"{first.prefix}{indent}{first.value}" for leaf in leaves: res += str(leaf) - for comment in self.comments.values(): + for _, comment in self.comments: res += str(comment) - return res + '\n' + return res + "\n" def __bool__(self) -> bool: + """Return True if the line has leaves or comments.""" return bool(self.leaves or self.comments) +class UnformattedLines(Line): + """Just like :class:`Line` but stores lines which aren't reformatted.""" + + def append(self, leaf: Leaf, preformatted: bool = True) -> None: + """Just add a new `leaf` to the end of the lines. + + The `preformatted` argument is ignored. + + Keeps track of indentation `depth`, which is useful when the user + says `# fmt: on`. Otherwise, doesn't do anything with the `leaf`. + """ + try: + list(generate_comments(leaf)) + except FormatOn as f_on: + self.leaves.append(f_on.leaf_from_consumed(leaf)) + raise + + self.leaves.append(leaf) + if leaf.type == token.INDENT: + self.depth += 1 + elif leaf.type == token.DEDENT: + self.depth -= 1 + + def __str__(self) -> str: + """Render unformatted lines from leaves which were added with `append()`. + + `depth` is not used for indentation in this case. + """ + if not self: + return "\n" + + res = "" + for leaf in self.leaves: + res += str(leaf) + return res + + def append_comment(self, comment: Leaf) -> bool: + """Not implemented in this class. Raises `NotImplementedError`.""" + raise NotImplementedError("Unformatted lines don't store comments separately.") + + def maybe_remove_trailing_comma(self, closing: Leaf) -> bool: + """Does nothing and returns False.""" + return False + + def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool: + """Does nothing and returns False.""" + return False + + @dataclass class EmptyLineTracker: """Provides a stateful method that returns the number of potential extra empty lines needed before and after the currently processed line. - Note: this tracker works on lines that haven't been split yet. + Note: this tracker works on lines that haven't been split yet. It assumes + the prefix of the first leaf consists of optional newlines. Those newlines + are consumed by `maybe_empty_lines()` and included in the computation. """ - previous_line: Optional[Line] = attrib(default=None) - previous_after: int = attrib(default=0) - previous_defs: List[int] = attrib(default=Factory(list)) + previous_line: Optional[Line] = None + previous_after: int = 0 + previous_defs: List[int] = Factory(list) def maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]: - """Returns the number of extra empty lines before and after the `current_line`. + """Return the number of extra empty lines before and after the `current_line`. - This is for separating `def`, `async def` and `class` with extra empty lines - (two on module-level), as well as providing an extra empty line after flow - control keywords to make them more prominent. + This is for separating `def`, `async def` and `class` with extra empty + lines (two on module-level), as well as providing an extra empty line + after flow control keywords to make them more prominent. """ + if isinstance(current_line, UnformattedLines): + return 0, 0 + before, after = self._maybe_empty_lines(current_line) + before -= self.previous_after self.previous_after = after self.previous_line = current_line return before, after def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]: - before = 0 + max_allowed = 1 + if current_line.depth == 0: + max_allowed = 2 + if current_line.leaves: + # Consume the first leaf's extra newlines. + first_leaf = current_line.leaves[0] + before = first_leaf.prefix.count("\n") + before = min(before, max_allowed) + first_leaf.prefix = "" + else: + before = 0 depth = current_line.depth while self.previous_defs and self.previous_defs[-1] >= depth: self.previous_defs.pop() - before = (1 if depth else 2) - self.previous_after + before = 1 if depth else 2 is_decorator = current_line.is_decorator if is_decorator or current_line.is_def or current_line.is_class: if not is_decorator: @@ -596,24 +949,23 @@ class EmptyLineTracker: newlines = 2 if current_line.depth: newlines -= 1 - newlines -= self.previous_after return newlines, 0 if current_line.is_flow_control: return before, 1 if ( - self.previous_line and - self.previous_line.is_import and - not current_line.is_import and - depth == self.previous_line.depth + self.previous_line + and self.previous_line.is_import + and not current_line.is_import + and depth == self.previous_line.depth ): return (before or 1), 0 if ( - self.previous_line and - self.previous_line.is_yield and - (not current_line.is_yield or depth != self.previous_line.depth) + self.previous_line + and self.previous_line.is_yield + and (not current_line.is_yield or depth != self.previous_line.depth) ): return (before or 1), 0 @@ -627,10 +979,9 @@ class LineGenerator(Visitor[Line]): Note: destroys the tree it's visiting by mutating prefixes of its leaves in ways that will no longer stringify to valid Python code on the tree. """ - current_line: Line = attrib(default=Factory(Line)) - standalone_comments: List[Leaf] = attrib(default=Factory(list)) + current_line: Line = Factory(Line) - def line(self, indent: int = 0) -> Iterator[Line]: + def line(self, indent: int = 0, type: Type[Line] = Line) -> Iterator[Line]: """Generate a line. If the line is empty, only emit if it makes sense. @@ -639,59 +990,87 @@ class LineGenerator(Visitor[Line]): If any lines were generated, set up a new current_line. """ if not self.current_line: - self.current_line.depth += indent + if self.current_line.__class__ == type: + self.current_line.depth += indent + else: + self.current_line = type(depth=self.current_line.depth + indent) return # Line is empty, don't emit. Creating a new one unnecessary. complete_line = self.current_line - self.current_line = Line(depth=complete_line.depth + indent) + self.current_line = type(depth=complete_line.depth + indent) yield complete_line + def visit(self, node: LN) -> Iterator[Line]: + """Main method to visit `node` and its children. + + Yields :class:`Line` objects. + """ + if isinstance(self.current_line, UnformattedLines): + # File contained `# fmt: off` + yield from self.visit_unformatted(node) + + else: + yield from super().visit(node) + def visit_default(self, node: LN) -> Iterator[Line]: + """Default `visit_*()` implementation. Recurses to children of `node`.""" if isinstance(node, Leaf): - for comment in generate_comments(node): - if self.current_line.bracket_tracker.any_open_brackets(): - # any comment within brackets is subject to splitting - self.current_line.append(comment) - elif comment.type == token.COMMENT: - # regular trailing comment - self.current_line.append(comment) - yield from self.line() - - else: - # regular standalone comment, to be processed later (see - # docstring in `generate_comments()` - self.standalone_comments.append(comment) - normalize_prefix(node) - if node.type not in WHITESPACE: - for comment in self.standalone_comments: - yield from self.line() - - self.current_line.append(comment) - yield from self.line() - - self.standalone_comments = [] - self.current_line.append(node) + any_open_brackets = self.current_line.bracket_tracker.any_open_brackets() + try: + for comment in generate_comments(node): + if any_open_brackets: + # any comment within brackets is subject to splitting + self.current_line.append(comment) + elif comment.type == token.COMMENT: + # regular trailing comment + self.current_line.append(comment) + yield from self.line() + + else: + # regular standalone comment + yield from self.line() + + self.current_line.append(comment) + yield from self.line() + + except FormatOff as f_off: + f_off.trim_prefix(node) + yield from self.line(type=UnformattedLines) + yield from self.visit(node) + + except FormatOn as f_on: + # This only happens here if somebody says "fmt: on" multiple + # times in a row. + f_on.trim_prefix(node) + yield from self.visit_default(node) + + else: + normalize_prefix(node, inside_brackets=any_open_brackets) + if node.type == token.STRING: + normalize_string_quotes(node) + if node.type not in WHITESPACE: + self.current_line.append(node) yield from super().visit_default(node) - def visit_suite(self, node: Node) -> Iterator[Line]: - """Body of a statement after a colon.""" - children = iter(node.children) - # Process newline before indenting. It might contain an inline - # comment that should go right after the colon. - newline = next(children) - yield from self.visit(newline) + def visit_INDENT(self, node: Node) -> Iterator[Line]: + """Increase indentation level, maybe yield a line.""" + # In blib2to3 INDENT never holds comments. yield from self.line(+1) + yield from self.visit_default(node) - for child in children: - yield from self.visit(child) - + def visit_DEDENT(self, node: Node) -> Iterator[Line]: + """Decrease indentation level, maybe yield a line.""" + # DEDENT has no value. Additionally, in blib2to3 it never holds comments. yield from self.line(-1) def visit_stmt(self, node: Node, keywords: Set[str]) -> Iterator[Line]: """Visit a statement. - The relevant Python language keywords for this statement are NAME leaves - within it. + This implementation is shared for `if`, `while`, `for`, `try`, `except`, + `def`, `with`, and `class`. + + The relevant Python language `keywords` for a given statement will be NAME + leaves within it. This methods puts those on a separate line. """ for child in node.children: if child.type == token.NAME and child.value in keywords: # type: ignore @@ -700,7 +1079,7 @@ class LineGenerator(Visitor[Line]): yield from self.visit(child) def visit_simple_stmt(self, node: Node) -> Iterator[Line]: - """A statement without nested statements.""" + """Visit a statement without nested statements.""" is_suite_like = node.parent and node.parent.type in STATEMENT if is_suite_like: yield from self.line(+1) @@ -712,13 +1091,14 @@ class LineGenerator(Visitor[Line]): yield from self.visit_default(node) def visit_async_stmt(self, node: Node) -> Iterator[Line]: + """Visit `async def`, `async for`, `async with`.""" yield from self.line() children = iter(node.children) for child in children: yield from self.visit(child) - if child.type == token.NAME and child.value == 'async': # type: ignore + if child.type == token.ASYNC: break internal_stmt = next(children) @@ -726,28 +1106,49 @@ class LineGenerator(Visitor[Line]): yield from self.visit(child) def visit_decorators(self, node: Node) -> Iterator[Line]: + """Visit decorators.""" for child in node.children: yield from self.line() yield from self.visit(child) def visit_SEMI(self, leaf: Leaf) -> Iterator[Line]: + """Remove a semicolon and put the other statement on a separate line.""" yield from self.line() def visit_ENDMARKER(self, leaf: Leaf) -> Iterator[Line]: + """End of file. Process outstanding comments and end with a newline.""" yield from self.visit_default(leaf) yield from self.line() + def visit_unformatted(self, node: LN) -> Iterator[Line]: + """Used when file contained a `# fmt: off`.""" + if isinstance(node, Node): + for child in node.children: + yield from self.visit(child) + + else: + try: + self.current_line.append(node) + except FormatOn as f_on: + f_on.trim_prefix(node) + yield from self.line() + yield from self.visit(node) + + if node.type == token.ENDMARKER: + # somebody decided not to put a final `# fmt: on` + yield from self.line() + def __attrs_post_init__(self) -> None: """You are in a twisty little maze of passages.""" v = self.visit_stmt - self.visit_if_stmt = partial(v, keywords={'if', 'else', 'elif'}) - self.visit_while_stmt = partial(v, keywords={'while', 'else'}) - self.visit_for_stmt = partial(v, keywords={'for', 'else'}) - self.visit_try_stmt = partial(v, keywords={'try', 'except', 'else', 'finally'}) - self.visit_except_clause = partial(v, keywords={'except'}) - self.visit_funcdef = partial(v, keywords={'def'}) - self.visit_with_stmt = partial(v, keywords={'with'}) - self.visit_classdef = partial(v, keywords={'class'}) + self.visit_if_stmt = partial(v, keywords={"if", "else", "elif"}) + self.visit_while_stmt = partial(v, keywords={"while", "else"}) + self.visit_for_stmt = partial(v, keywords={"for", "else"}) + self.visit_try_stmt = partial(v, keywords={"try", "except", "else", "finally"}) + self.visit_except_clause = partial(v, keywords={"except"}) + self.visit_funcdef = partial(v, keywords={"def"}) + self.visit_with_stmt = partial(v, keywords={"with"}) + self.visit_classdef = partial(v, keywords={"class"}) self.visit_async_funcdef = self.visit_async_stmt self.visit_decorated = self.visit_decorators @@ -756,53 +1157,103 @@ BRACKET = {token.LPAR: token.RPAR, token.LSQB: token.RSQB, token.LBRACE: token.R OPENING_BRACKETS = set(BRACKET.keys()) CLOSING_BRACKETS = set(BRACKET.values()) BRACKETS = OPENING_BRACKETS | CLOSING_BRACKETS +ALWAYS_NO_SPACE = CLOSING_BRACKETS | {token.COMMA, STANDALONE_COMMENT} -def whitespace(leaf: Leaf) -> str: +def whitespace(leaf: Leaf) -> str: # noqa C901 """Return whitespace prefix if needed for the given `leaf`.""" - NO = '' - SPACE = ' ' - DOUBLESPACE = ' ' + NO = "" + SPACE = " " + DOUBLESPACE = " " t = leaf.type p = leaf.parent v = leaf.value - if t == token.COLON: + if t in ALWAYS_NO_SPACE: return NO - if t == token.COMMA: - return NO + if t == token.COMMENT: + return DOUBLESPACE - if t == token.RPAR: + assert p is not None, f"INTERNAL ERROR: hand-made leaf without parent: {leaf!r}" + if t == token.COLON and p.type not in {syms.subscript, syms.subscriptlist}: return NO - if t == token.COMMENT: - return DOUBLESPACE + prev = leaf.prev_sibling + if not prev: + prevp = preceding_leaf(p) + if not prevp or prevp.type in OPENING_BRACKETS: + return NO - if t == STANDALONE_COMMENT: + if t == token.COLON: + return SPACE if prevp.type == token.COMMA else NO + + if prevp.type == token.EQUAL: + if prevp.parent: + if prevp.parent.type in { + syms.arglist, syms.argument, syms.parameters, syms.varargslist + }: + return NO + + elif prevp.parent.type == syms.typedargslist: + # A bit hacky: if the equal sign has whitespace, it means we + # previously found it's a typed argument. So, we're using + # that, too. + return prevp.prefix + + elif prevp.type == token.DOUBLESTAR: + if prevp.parent and prevp.parent.type in { + syms.arglist, + syms.argument, + syms.dictsetmaker, + syms.parameters, + syms.typedargslist, + syms.varargslist, + }: + return NO + + elif prevp.type == token.COLON: + if prevp.parent and prevp.parent.type in {syms.subscript, syms.sliceop}: + return NO + + elif ( + prevp.parent + and prevp.parent.type in {syms.factor, syms.star_expr} + and prevp.type in MATH_OPERATORS + ): + return NO + + elif ( + prevp.type == token.RIGHTSHIFT + and prevp.parent + and prevp.parent.type == syms.shift_expr + and prevp.prev_sibling + and prevp.prev_sibling.type == token.NAME + and prevp.prev_sibling.value == "print" # type: ignore + ): + # Python 2 print chevron + return NO + + elif prev.type in OPENING_BRACKETS: return NO - assert p is not None, f"INTERNAL ERROR: hand-made leaf without parent: {leaf!r}" if p.type in {syms.parameters, syms.arglist}: # untyped function signatures or calls if t == token.RPAR: return NO - prev = leaf.prev_sibling if not prev or prev.type != token.COMMA: return NO - if p.type == syms.varargslist: + elif p.type == syms.varargslist: # lambdas if t == token.RPAR: return NO - prev = leaf.prev_sibling if prev and prev.type != token.COMMA: return NO elif p.type == syms.typedargslist: # typed function signatures - prev = leaf.prev_sibling if not prev: return NO @@ -820,7 +1271,6 @@ def whitespace(leaf: Leaf) -> str: elif p.type == syms.tname: # type names - prev = leaf.prev_sibling if not prev: prevp = preceding_leaf(p) if not prevp or prevp.type != token.COMMA: @@ -831,7 +1281,6 @@ def whitespace(leaf: Leaf) -> str: if t == token.LPAR or t == token.RPAR: return NO - prev = leaf.prev_sibling if not prev: if t == token.DOT: prevp = preceding_leaf(p) @@ -849,7 +1298,6 @@ def whitespace(leaf: Leaf) -> str: if t == token.EQUAL: return NO - prev = leaf.prev_sibling if not prev: prevp = preceding_leaf(p) if not prevp or prevp.type == token.LPAR: @@ -863,7 +1311,6 @@ def whitespace(leaf: Leaf) -> str: return NO elif p.type == syms.dotted_name: - prev = leaf.prev_sibling if prev: return NO @@ -875,101 +1322,45 @@ def whitespace(leaf: Leaf) -> str: if t == token.LPAR: return NO - prev = leaf.prev_sibling if prev and prev.type == token.LPAR: return NO elif p.type == syms.subscript: # indexing - if t == token.COLON: - return NO - - prev = leaf.prev_sibling - if not prev or prev.type == token.COLON: - return NO - - elif p.type in { - syms.test, - syms.not_test, - syms.xor_expr, - syms.or_test, - syms.and_test, - syms.arith_expr, - syms.shift_expr, - syms.yield_expr, - syms.term, - syms.power, - syms.comparison, - }: - # various arithmetic and logic expressions - prev = leaf.prev_sibling if not prev: - prevp = preceding_leaf(p) - if not prevp or prevp.type in OPENING_BRACKETS: - return NO - - if prevp.type == token.EQUAL: - if prevp.parent and prevp.parent.type in { - syms.varargslist, syms.parameters, syms.arglist, syms.argument - }: - return NO - - return SPACE + assert p.parent is not None, "subscripts are always parented" + if p.parent.type == syms.subscriptlist: + return SPACE - elif p.type == syms.atom: - if t in CLOSING_BRACKETS: return NO - prev = leaf.prev_sibling - if not prev: - prevp = preceding_leaf(p) - if not prevp: - return NO - - if prevp.type in OPENING_BRACKETS: - return NO - - if prevp.type == token.EQUAL: - if prevp.parent and prevp.parent.type in { - syms.varargslist, syms.parameters, syms.arglist, syms.argument - }: - return NO - - if prevp.type == token.DOUBLESTAR: - if prevp.parent and prevp.parent.type in { - syms.varargslist, syms.parameters, syms.arglist, syms.dictsetmaker - }: - return NO - - elif prev.type in OPENING_BRACKETS: + else: return NO - elif t == token.DOT: + elif p.type == syms.atom: + if prev and t == token.DOT: # dots, but not the first one. return NO elif ( - p.type == syms.listmaker or - p.type == syms.testlist_gexp or - p.type == syms.subscriptlist + p.type == syms.listmaker + or p.type == syms.testlist_gexp + or p.type == syms.subscriptlist ): # list interior, including unpacking - prev = leaf.prev_sibling if not prev: return NO elif p.type == syms.dictsetmaker: # dict and set interior, including unpacking - prev = leaf.prev_sibling if not prev: return NO if prev.type == token.DOUBLESTAR: return NO - elif p.type == syms.factor or p.type == syms.star_expr: + elif p.type in {syms.factor, syms.star_expr}: # unary ops - prev = leaf.prev_sibling if not prev: prevp = preceding_leaf(p) if not prevp or prevp.type in OPENING_BRACKETS: @@ -990,15 +1381,13 @@ def whitespace(leaf: Leaf) -> str: elif p.type == syms.import_from: if t == token.DOT: - prev = leaf.prev_sibling if prev and prev.type == token.DOT: return NO elif t == token.NAME: - if v == 'import': + if v == "import": return SPACE - prev = leaf.prev_sibling if prev and prev.type == token.DOT: return NO @@ -1009,7 +1398,7 @@ def whitespace(leaf: Leaf) -> str: def preceding_leaf(node: Optional[LN]) -> Optional[Leaf]: - """Returns the first leaf that precedes `node`, if any.""" + """Return the first leaf that precedes `node`, if any.""" while node: res = node.prev_sibling if res: @@ -1026,32 +1415,87 @@ def preceding_leaf(node: Optional[LN]) -> Optional[Leaf]: return None -def is_delimiter(leaf: Leaf) -> int: - """Returns the priority of the `leaf` delimiter. Returns 0 if not delimiter. +def is_split_after_delimiter(leaf: Leaf, previous: Leaf = None) -> int: + """Return the priority of the `leaf` delimiter, given a line break after it. + + The delimiter priorities returned here are from those delimiters that would + cause a line break after themselves. Higher numbers are higher priority. """ if leaf.type == token.COMMA: return COMMA_PRIORITY - if leaf.type == token.NAME and leaf.value in LOGIC_OPERATORS: - return LOGIC_PRIORITY + if ( + leaf.type in VARARGS + and leaf.parent + and leaf.parent.type in {syms.argument, syms.typedargslist} + ): + return MATH_PRIORITY + + return 0 + + +def is_split_before_delimiter(leaf: Leaf, previous: Leaf = None) -> int: + """Return the priority of the `leaf` delimiter, given a line before after it. + + The delimiter priorities returned here are from those delimiters that would + cause a line break before themselves. + + Higher numbers are higher priority. + """ + if ( + leaf.type in MATH_OPERATORS + and leaf.parent + and leaf.parent.type not in {syms.factor, syms.star_expr} + ): + return MATH_PRIORITY if leaf.type in COMPARATORS: return COMPARATOR_PRIORITY if ( - leaf.type in MATH_OPERATORS and - leaf.parent and - leaf.parent.type not in {syms.factor, syms.star_expr} + leaf.type == token.STRING + and previous is not None + and previous.type == token.STRING ): - return MATH_PRIORITY + return STRING_PRIORITY + + if ( + leaf.type == token.NAME + and leaf.value == "for" + and leaf.parent + and leaf.parent.type in {syms.comp_for, syms.old_comp_for} + ): + return COMPREHENSION_PRIORITY + + if ( + leaf.type == token.NAME + and leaf.value == "if" + and leaf.parent + and leaf.parent.type in {syms.comp_if, syms.old_comp_if} + ): + return COMPREHENSION_PRIORITY + + if leaf.type == token.NAME and leaf.value in LOGIC_OPERATORS and leaf.parent: + return LOGIC_PRIORITY return 0 +def is_delimiter(leaf: Leaf, previous: Leaf = None) -> int: + """Return the priority of the `leaf` delimiter. Return 0 if not delimiter. + + Higher numbers are higher priority. + """ + return max( + is_split_before_delimiter(leaf, previous), + is_split_after_delimiter(leaf, previous), + ) + + def generate_comments(leaf: Leaf) -> Iterator[Leaf]: - """Cleans the prefix of the `leaf` and generates comments from it, if any. + """Clean the prefix of the `leaf` and generate comments from it, if any. Comments in lib2to3 are shoved into the whitespace prefix. This happens in `pgen2/driver.py:Driver.parse_tokens()`. This was a brilliant implementation @@ -1069,53 +1513,94 @@ def generate_comments(leaf: Leaf) -> Iterator[Leaf]: Inline comments are emitted as regular token.COMMENT leaves. Standalone are emitted with a fake STANDALONE_COMMENT token identifier. """ - if not leaf.prefix: + p = leaf.prefix + if not p: return - if '#' not in leaf.prefix: + if "#" not in p: return - before_comment, content = leaf.prefix.split('#', 1) - content = content.rstrip() - if content and (content[0] not in {' ', '!', '#'}): - content = ' ' + content - is_standalone_comment = ( - '\n' in before_comment or '\n' in content or leaf.type == token.DEDENT - ) - if not is_standalone_comment: - # simple trailing comment - yield Leaf(token.COMMENT, value='#' + content) - return - - for line in ('#' + content).split('\n'): + consumed = 0 + nlines = 0 + for index, line in enumerate(p.split("\n")): + consumed += len(line) + 1 # adding the length of the split '\n' line = line.lstrip() - if not line.startswith('#'): + if not line: + nlines += 1 + if not line.startswith("#"): continue - yield Leaf(STANDALONE_COMMENT, line) + if index == 0 and leaf.type != token.ENDMARKER: + comment_type = token.COMMENT # simple trailing comment + else: + comment_type = STANDALONE_COMMENT + comment = make_comment(line) + yield Leaf(comment_type, comment, prefix="\n" * nlines) + + if comment in {"# fmt: on", "# yapf: enable"}: + raise FormatOn(consumed) + if comment in {"# fmt: off", "# yapf: disable"}: + if comment_type == STANDALONE_COMMENT: + raise FormatOff(consumed) -def split_line(line: Line, line_length: int, inner: bool = False) -> Iterator[Line]: - """Splits a `line` into potentially many lines. + prev = preceding_leaf(leaf) + if not prev or prev.type in WHITESPACE: # standalone comment in disguise + raise FormatOff(consumed) + + nlines = 0 + + +def make_comment(content: str) -> str: + """Return a consistently formatted comment from the given `content` string. + + All comments (except for "##", "#!", "#:") should have a single space between + the hash sign and the content. + + If `content` didn't start with a hash sign, one is provided. + """ + content = content.rstrip() + if not content: + return "#" + + if content[0] == "#": + content = content[1:] + if content and content[0] not in " !:#": + content = " " + content + return "#" + content + + +def split_line( + line: Line, line_length: int, inner: bool = False, py36: bool = False +) -> Iterator[Line]: + """Split a `line` into potentially many lines. They should fit in the allotted `line_length` but might not be able to. `inner` signifies that there were a pair of brackets somewhere around the current `line`, possibly transitively. This means we can fallback to splitting by delimiters if the LHS/RHS don't yield any results. + + If `py36` is True, splitting may generate syntax that is only compatible + with Python 3.6 and later. """ - line_str = str(line).strip('\n') - if len(line_str) <= line_length and '\n' not in line_str: + if isinstance(line, UnformattedLines) or line.is_comment: yield line return + line_str = str(line).strip("\n") + if ( + len(line_str) <= line_length + and "\n" not in line_str # multiline strings + and not line.contains_standalone_comments + ): + yield line + return + + split_funcs: List[SplitFunc] if line.is_def: split_funcs = [left_hand_split] elif line.inside_brackets: - split_funcs = [delimiter_split] - if '\n' not in line_str: - # Only attempt RHS if we don't have multiline strings or comments - # on this line. - split_funcs.append(right_hand_split) + split_funcs = [delimiter_split, standalone_comment_split, right_hand_split] else: split_funcs = [right_hand_split] for split_func in split_funcs: @@ -1124,11 +1609,13 @@ def split_line(line: Line, line_length: int, inner: bool = False) -> Iterator[Li # split altogether. result: List[Line] = [] try: - for l in split_func(line): - if str(l).strip('\n') == line_str: + for l in split_func(line, py36): + if str(l).strip("\n") == line_str: raise CannotSplit("Split function returned an unchanged result") - result.extend(split_line(l, line_length=line_length, inner=True)) + result.extend( + split_line(l, line_length=line_length, inner=True, py36=py36) + ) except CannotSplit as cs: continue @@ -1140,7 +1627,7 @@ def split_line(line: Line, line_length: int, inner: bool = False) -> Iterator[Li yield line -def left_hand_split(line: Line) -> Iterator[Line]: +def left_hand_split(line: Line, py36: bool = False) -> Iterator[Line]: """Split line into many lines, starting with the first matching bracket pair. Note: this usually looks weird, only use this for function definitions. @@ -1156,11 +1643,11 @@ def left_hand_split(line: Line) -> Iterator[Line]: matching_bracket = None for leaf in line.leaves: if ( - current_leaves is body_leaves and - leaf.type in CLOSING_BRACKETS and - leaf.opening_bracket is matching_bracket # type: ignore + current_leaves is body_leaves + and leaf.type in CLOSING_BRACKETS + and leaf.opening_bracket is matching_bracket ): - current_leaves = tail_leaves + current_leaves = tail_leaves if body_leaves else head_leaves current_leaves.append(leaf) if current_leaves is head_leaves: if leaf.type in OPENING_BRACKETS: @@ -1168,34 +1655,22 @@ def left_hand_split(line: Line) -> Iterator[Line]: current_leaves = body_leaves # Since body is a new indent level, remove spurious leading whitespace. if body_leaves: - normalize_prefix(body_leaves[0]) + normalize_prefix(body_leaves[0], inside_brackets=True) # Build the new lines. for result, leaves in ( (head, head_leaves), (body, body_leaves), (tail, tail_leaves) ): for leaf in leaves: result.append(leaf, preformatted=True) - comment_after = line.comments.get(id(leaf)) - if comment_after: + for comment_after in line.comments_after(leaf): result.append(comment_after, preformatted=True) - # Check if the split succeeded. - tail_len = len(str(tail)) - if not body: - if tail_len == 0: - raise CannotSplit("Splitting brackets produced the same line") - - elif tail_len < 3: - raise CannotSplit( - f"Splitting brackets on an empty body to save " - f"{tail_len} characters is not worth it" - ) - + bracket_split_succeeded_or_raise(head, body, tail) for result in (head, body, tail): if result: yield result -def right_hand_split(line: Line) -> Iterator[Line]: +def right_hand_split(line: Line, py36: bool = False) -> Iterator[Line]: """Split line into many lines, starting with the last matching bracket pair.""" head = Line(depth=line.depth) body = Line(depth=line.depth + 1, inside_brackets=True) @@ -1208,29 +1683,47 @@ def right_hand_split(line: Line) -> Iterator[Line]: for leaf in reversed(line.leaves): if current_leaves is body_leaves: if leaf is opening_bracket: - current_leaves = head_leaves + current_leaves = head_leaves if body_leaves else tail_leaves current_leaves.append(leaf) if current_leaves is tail_leaves: if leaf.type in CLOSING_BRACKETS: - opening_bracket = leaf.opening_bracket # type: ignore + opening_bracket = leaf.opening_bracket current_leaves = body_leaves tail_leaves.reverse() body_leaves.reverse() head_leaves.reverse() # Since body is a new indent level, remove spurious leading whitespace. if body_leaves: - normalize_prefix(body_leaves[0]) + normalize_prefix(body_leaves[0], inside_brackets=True) # Build the new lines. for result, leaves in ( (head, head_leaves), (body, body_leaves), (tail, tail_leaves) ): for leaf in leaves: result.append(leaf, preformatted=True) - comment_after = line.comments.get(id(leaf)) - if comment_after: + for comment_after in line.comments_after(leaf): result.append(comment_after, preformatted=True) - # Check if the split succeeded. - tail_len = len(str(tail).strip('\n')) + bracket_split_succeeded_or_raise(head, body, tail) + for result in (head, body, tail): + if result: + yield result + + +def bracket_split_succeeded_or_raise(head: Line, body: Line, tail: Line) -> None: + """Raise :exc:`CannotSplit` if the last left- or right-hand split failed. + + Do nothing otherwise. + + A left- or right-hand split is based on a pair of brackets. Content before + (and including) the opening bracket is left on one line, content inside the + brackets is put on a separate line, and finally content starting with and + following the closing bracket is put on a separate line. + + Those are called `head`, `body`, and `tail`, respectively. If the split + produced the same line (all content in `head`) or ended up with an empty `body` + and the `tail` is just the closing bracket, then it's considered failed. + """ + tail_len = len(str(tail).strip()) if not body: if tail_len == 0: raise CannotSplit("Splitting brackets produced the same line") @@ -1241,15 +1734,28 @@ def right_hand_split(line: Line) -> Iterator[Line]: f"{tail_len} characters is not worth it" ) - for result in (head, body, tail): - if result: - yield result + +def dont_increase_indentation(split_func: SplitFunc) -> SplitFunc: + """Normalize prefix of the first leaf in every line returned by `split_func`. + + This is a decorator over relevant split functions. + """ + + @wraps(split_func) + def split_wrapper(line: Line, py36: bool = False) -> Iterator[Line]: + for l in split_func(line, py36): + normalize_prefix(l.leaves[0], inside_brackets=True) + yield l + + return split_wrapper -def delimiter_split(line: Line) -> Iterator[Line]: +@dont_increase_indentation +def delimiter_split(line: Line, py36: bool = False) -> Iterator[Line]: """Split according to delimiters of the highest priority. - This kind of split doesn't increase indentation. + If `py36` is True, the split will add trailing commas also in function + signatures that contain `*` and `**`. """ try: last_leaf = line.leaves[-1] @@ -1258,67 +1764,201 @@ def delimiter_split(line: Line) -> Iterator[Line]: delimiters = line.bracket_tracker.delimiters try: - delimiter_priority = line.bracket_tracker.max_priority(exclude={id(last_leaf)}) + delimiter_priority = line.bracket_tracker.max_delimiter_priority( + exclude={id(last_leaf)} + ) except ValueError: raise CannotSplit("No delimiters found") current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets) + lowest_depth = sys.maxsize + trailing_comma_safe = True + + def append_to_line(leaf: Leaf) -> Iterator[Line]: + """Append `leaf` to current line or to new line if appending impossible.""" + nonlocal current_line + try: + current_line.append_safe(leaf, preformatted=True) + except ValueError as ve: + yield current_line + + current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets) + current_line.append(leaf) + for leaf in line.leaves: - current_line.append(leaf, preformatted=True) - comment_after = line.comments.get(id(leaf)) - if comment_after: - current_line.append(comment_after, preformatted=True) + yield from append_to_line(leaf) + + for comment_after in line.comments_after(leaf): + yield from append_to_line(comment_after) + + lowest_depth = min(lowest_depth, leaf.bracket_depth) + if ( + leaf.bracket_depth == lowest_depth + and leaf.type == token.STAR + or leaf.type == token.DOUBLESTAR + ): + trailing_comma_safe = trailing_comma_safe and py36 leaf_priority = delimiters.get(id(leaf)) if leaf_priority == delimiter_priority: - normalize_prefix(current_line.leaves[0]) yield current_line current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets) if current_line: if ( - delimiter_priority == COMMA_PRIORITY and - current_line.leaves[-1].type != token.COMMA + trailing_comma_safe + and delimiter_priority == COMMA_PRIORITY + and current_line.leaves[-1].type != token.COMMA + and current_line.leaves[-1].type != STANDALONE_COMMENT ): - current_line.append(Leaf(token.COMMA, ',')) - normalize_prefix(current_line.leaves[0]) + current_line.append(Leaf(token.COMMA, ",")) + yield current_line + + +@dont_increase_indentation +def standalone_comment_split(line: Line, py36: bool = False) -> Iterator[Line]: + """Split standalone comments from the rest of the line.""" + for leaf in line.leaves: + if leaf.type == STANDALONE_COMMENT: + if leaf.bracket_depth == 0: + break + + else: + raise CannotSplit("Line does not have any standalone comments") + + current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets) + + def append_to_line(leaf: Leaf) -> Iterator[Line]: + """Append `leaf` to current line or to new line if appending impossible.""" + nonlocal current_line + try: + current_line.append_safe(leaf, preformatted=True) + except ValueError as ve: + yield current_line + + current_line = Line(depth=line.depth, inside_brackets=line.inside_brackets) + current_line.append(leaf) + + for leaf in line.leaves: + yield from append_to_line(leaf) + + for comment_after in line.comments_after(leaf): + yield from append_to_line(comment_after) + + if current_line: yield current_line def is_import(leaf: Leaf) -> bool: - """Returns True if the given leaf starts an import statement.""" + """Return True if the given leaf starts an import statement.""" p = leaf.parent t = leaf.type v = leaf.value return bool( - t == token.NAME and - ( - (v == 'import' and p and p.type == syms.import_name) or - (v == 'from' and p and p.type == syms.import_from) + t == token.NAME + and ( + (v == "import" and p and p.type == syms.import_name) + or (v == "from" and p and p.type == syms.import_from) ) ) -def normalize_prefix(leaf: Leaf) -> None: - """Leave existing extra newlines for imports. Remove everything else.""" - if is_import(leaf): - spl = leaf.prefix.split('#', 1) - nl_count = spl[0].count('\n') - if len(spl) > 1: - # Skip one newline since it was for a standalone comment. - nl_count -= 1 - leaf.prefix = '\n' * nl_count +def normalize_prefix(leaf: Leaf, *, inside_brackets: bool) -> None: + """Leave existing extra newlines if not `inside_brackets`. Remove everything + else. + + Note: don't use backslashes for formatting or you'll lose your voting rights. + """ + if not inside_brackets: + spl = leaf.prefix.split("#") + if "\\" not in spl[0]: + nl_count = spl[-1].count("\n") + if len(spl) > 1: + nl_count -= 1 + leaf.prefix = "\n" * nl_count + return + + leaf.prefix = "" + + +def normalize_string_quotes(leaf: Leaf) -> None: + """Prefer double quotes but only if it doesn't cause more escaping. + + Adds or removes backslashes as appropriate. Doesn't parse and fix + strings nested in f-strings (yet). + + Note: Mutates its argument. + """ + value = leaf.value.lstrip("furbFURB") + if value[:3] == '"""': return - leaf.prefix = '' + elif value[:3] == "'''": + orig_quote = "'''" + new_quote = '"""' + elif value[0] == '"': + orig_quote = '"' + new_quote = "'" + else: + orig_quote = "'" + new_quote = '"' + first_quote_pos = leaf.value.find(orig_quote) + if first_quote_pos == -1: + return # There's an internal error + + body = leaf.value[first_quote_pos + len(orig_quote):-len(orig_quote)] + new_body = body.replace(f"\\{orig_quote}", orig_quote).replace( + new_quote, f"\\{new_quote}" + ) + if new_quote == '"""' and new_body[-1] == '"': + # edge case: + new_body = new_body[:-1] + '\\"' + orig_escape_count = body.count("\\") + new_escape_count = new_body.count("\\") + if new_escape_count > orig_escape_count: + return # Do not introduce more escaping + + if new_escape_count == orig_escape_count and orig_quote == '"': + return # Prefer double quotes + + prefix = leaf.value[:first_quote_pos] + leaf.value = f"{prefix}{new_quote}{new_body}{new_quote}" + + +def is_python36(node: Node) -> bool: + """Return True if the current file is using Python 3.6+ features. + + Currently looking for: + - f-strings; and + - trailing commas after * or ** in function signatures. + """ + for n in node.pre_order(): + if n.type == token.STRING: + value_head = n.value[:2] # type: ignore + if value_head in {'f"', 'F"', "f'", "F'", "rf", "fr", "RF", "FR"}: + return True + + elif ( + n.type == syms.typedargslist + and n.children + and n.children[-1].type == token.COMMA + ): + for ch in n.children: + if ch.type == token.STAR or ch.type == token.DOUBLESTAR: + return True + + return False -PYTHON_EXTENSIONS = {'.py'} +PYTHON_EXTENSIONS = {".py"} BLACKLISTED_DIRECTORIES = { - 'build', 'buck-out', 'dist', '_build', '.git', '.hg', '.mypy_cache', '.tox', '.venv' + "build", "buck-out", "dist", "_build", ".git", ".hg", ".mypy_cache", ".tox", ".venv" } def gen_python_files_in_dir(path: Path) -> Iterator[Path]: + """Generate all files under `path` which aren't under BLACKLISTED_DIRECTORIES + and have one of the PYTHON_EXTENSIONS. + """ for child in path.iterdir(): if child.is_dir(): if child.name in BLACKLISTED_DIRECTORIES: @@ -1332,59 +1972,78 @@ def gen_python_files_in_dir(path: Path) -> Iterator[Path]: @dataclass class Report: - """Provides a reformatting counter.""" - change_count: int = attrib(default=0) - same_count: int = attrib(default=0) - failure_count: int = attrib(default=0) + """Provides a reformatting counter. Can be rendered with `str(report)`.""" + check: bool = False + change_count: int = 0 + same_count: int = 0 + failure_count: int = 0 def done(self, src: Path, changed: bool) -> None: """Increment the counter for successful reformatting. Write out a message.""" if changed: - out(f'reformatted {src}') + reformatted = "would reformat" if self.check else "reformatted" + out(f"{reformatted} {src}") self.change_count += 1 else: - out(f'{src} already well formatted, good job.', bold=False) + out(f"{src} already well formatted, good job.", bold=False) self.same_count += 1 def failed(self, src: Path, message: str) -> None: """Increment the counter for failed reformatting. Write out a message.""" - err(f'error: cannot format {src}: {message}') + err(f"error: cannot format {src}: {message}") self.failure_count += 1 @property def return_code(self) -> int: - """Which return code should the app use considering the current state.""" - return 1 if self.failure_count else 0 + """Return the exit code that the app should use. + + This considers the current state of changed files and failures: + - if there were any failures, return 123; + - if any files were changed and --check is being used, return 1; + - otherwise return 0. + """ + # According to http://tldp.org/LDP/abs/html/exitcodes.html starting with + # 126 we have special returncodes reserved by the shell. + if self.failure_count: + return 123 + + elif self.change_count and self.check: + return 1 + + return 0 def __str__(self) -> str: - """A color report of the current state. + """Render a color report of the current state. Use `click.unstyle` to remove colors. """ + if self.check: + reformatted = "would be reformatted" + unchanged = "would be left unchanged" + failed = "would fail to reformat" + else: + reformatted = "reformatted" + unchanged = "left unchanged" + failed = "failed to reformat" report = [] if self.change_count: - s = 's' if self.change_count > 1 else '' + s = "s" if self.change_count > 1 else "" report.append( - click.style(f'{self.change_count} file{s} reformatted', bold=True) + click.style(f"{self.change_count} file{s} {reformatted}", bold=True) ) if self.same_count: - s = 's' if self.same_count > 1 else '' - report.append(f'{self.same_count} file{s} left unchanged') + s = "s" if self.same_count > 1 else "" + report.append(f"{self.same_count} file{s} {unchanged}") if self.failure_count: - s = 's' if self.failure_count > 1 else '' + s = "s" if self.failure_count > 1 else "" report.append( - click.style( - f'{self.failure_count} file{s} failed to reformat', fg='red' - ) + click.style(f"{self.failure_count} file{s} {failed}", fg="red") ) - return ', '.join(report) + '.' + return ", ".join(report) + "." def assert_equivalent(src: str, dst: str) -> None: - """Raises AssertionError if `src` and `dst` aren't equivalent. - - This is a temporary sanity check until Black becomes stable. - """ + """Raise AssertionError if `src` and `dst` aren't equivalent.""" import ast import traceback @@ -1417,72 +2076,104 @@ def assert_equivalent(src: str, dst: str) -> None: try: src_ast = ast.parse(src) except Exception as exc: - raise AssertionError(f"cannot parse source: {exc}") from None + major, minor = sys.version_info[:2] + raise AssertionError( + f"cannot use --safe with this file; failed to parse source file " + f"with Python {major}.{minor}'s builtin AST. Re-run with --fast " + f"or stop using deprecated Python 2 syntax. AST error message: {exc}" + ) try: dst_ast = ast.parse(dst) except Exception as exc: - log = dump_to_file(''.join(traceback.format_tb(exc.__traceback__)), dst) + log = dump_to_file("".join(traceback.format_tb(exc.__traceback__)), dst) raise AssertionError( f"INTERNAL ERROR: Black produced invalid code: {exc}. " f"Please report a bug on https://github.com/ambv/black/issues. " - f"This invalid output might be helpful: {log}", + f"This invalid output might be helpful: {log}" ) from None - src_ast_str = '\n'.join(_v(src_ast)) - dst_ast_str = '\n'.join(_v(dst_ast)) + src_ast_str = "\n".join(_v(src_ast)) + dst_ast_str = "\n".join(_v(dst_ast)) if src_ast_str != dst_ast_str: - log = dump_to_file(diff(src_ast_str, dst_ast_str, 'src', 'dst')) + log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst")) raise AssertionError( f"INTERNAL ERROR: Black produced code that is not equivalent to " f"the source. " f"Please report a bug on https://github.com/ambv/black/issues. " - f"This diff might be helpful: {log}", + f"This diff might be helpful: {log}" ) from None def assert_stable(src: str, dst: str, line_length: int) -> None: - """Raises AssertionError if `dst` reformats differently the second time. - - This is a temporary sanity check until Black becomes stable. - """ + """Raise AssertionError if `dst` reformats differently the second time.""" newdst = format_str(dst, line_length=line_length) if dst != newdst: log = dump_to_file( - diff(src, dst, 'source', 'first pass'), - diff(dst, newdst, 'first pass', 'second pass'), + diff(src, dst, "source", "first pass"), + diff(dst, newdst, "first pass", "second pass"), ) raise AssertionError( f"INTERNAL ERROR: Black produced different code on the second pass " f"of the formatter. " f"Please report a bug on https://github.com/ambv/black/issues. " - f"This diff might be helpful: {log}", + f"This diff might be helpful: {log}" ) from None def dump_to_file(*output: str) -> str: - """Dumps `output` to a temporary file. Returns path to the file.""" + """Dump `output` to a temporary file. Return path to the file.""" import tempfile with tempfile.NamedTemporaryFile( - mode='w', prefix='blk_', suffix='.log', delete=False + mode="w", prefix="blk_", suffix=".log", delete=False ) as f: for lines in output: f.write(lines) - f.write('\n') + if lines and lines[-1] != "\n": + f.write("\n") return f.name def diff(a: str, b: str, a_name: str, b_name: str) -> str: - """Returns a udiff string between strings `a` and `b`.""" + """Return a unified diff string between strings `a` and `b`.""" import difflib - a_lines = [line + '\n' for line in a.split('\n')] - b_lines = [line + '\n' for line in b.split('\n')] - return ''.join( + a_lines = [line + "\n" for line in a.split("\n")] + b_lines = [line + "\n" for line in b.split("\n")] + return "".join( difflib.unified_diff(a_lines, b_lines, fromfile=a_name, tofile=b_name, n=5) ) -if __name__ == '__main__': +def cancel(tasks: List[asyncio.Task]) -> None: + """asyncio signal handler that cancels all `tasks` and reports to stderr.""" + err("Aborted!") + for task in tasks: + task.cancel() + + +def shutdown(loop: BaseEventLoop) -> None: + """Cancel all pending tasks on `loop`, wait for them, and close the loop.""" + try: + # This part is borrowed from asyncio/runners.py in Python 3.7b2. + to_cancel = [task for task in asyncio.Task.all_tasks(loop) if not task.done()] + if not to_cancel: + return + + for task in to_cancel: + task.cancel() + loop.run_until_complete( + asyncio.gather(*to_cancel, loop=loop, return_exceptions=True) + ) + finally: + # `concurrent.futures.Future` objects cannot be cancelled once they + # are already running. There might be some when the `shutdown()` happened. + # Silence their logger's spew about the event loop being closed. + cf_logger = logging.getLogger("concurrent.futures") + cf_logger.setLevel(logging.CRITICAL) + loop.close() + + +if __name__ == "__main__": main()