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add --force-exclude argument (#1032)
[etc/vim.git] / black.py
index ff4f098db0271e964b9602553b38a1dcbd2455d6..614fa8ae5ceee9eb7f596a26a38f0d6b334965a1 100644 (file)
--- a/black.py
+++ b/black.py
@@ -2,7 +2,7 @@ import ast
 import asyncio
 from abc import ABC, abstractmethod
 from collections import defaultdict
-from concurrent.futures import Executor, ProcessPoolExecutor
+from concurrent.futures import Executor, ThreadPoolExecutor, ProcessPoolExecutor
 from contextlib import contextmanager
 from datetime import datetime
 from enum import Enum
@@ -34,11 +34,13 @@ from typing import (
     Pattern,
     Sequence,
     Set,
+    Sized,
     Tuple,
     Type,
     TypeVar,
     Union,
     cast,
+    TYPE_CHECKING,
 )
 from typing_extensions import Final
 from mypy_extensions import mypyc_attr
@@ -59,6 +61,9 @@ from blib2to3.pgen2.parse import ParseError
 
 from _black_version import version as __version__
 
+if TYPE_CHECKING:
+    import colorama  # noqa: F401
+
 DEFAULT_LINE_LENGTH = 88
 DEFAULT_EXCLUDES = r"/(\.eggs|\.git|\.hg|\.mypy_cache|\.nox|\.tox|\.venv|\.svn|_build|buck-out|build|dist)/"  # noqa: B950
 DEFAULT_INCLUDES = r"\.pyi?$"
@@ -140,12 +145,18 @@ class WriteBack(Enum):
     YES = 1
     DIFF = 2
     CHECK = 3
+    COLOR_DIFF = 4
 
     @classmethod
-    def from_configuration(cls, *, check: bool, diff: bool) -> "WriteBack":
+    def from_configuration(
+        cls, *, check: bool, diff: bool, color: bool = False
+    ) -> "WriteBack":
         if check and not diff:
             return cls.CHECK
 
+        if diff and color:
+            return cls.COLOR_DIFF
+
         return cls.DIFF if diff else cls.YES
 
 
@@ -296,6 +307,12 @@ def read_pyproject_toml(
     if not config:
         return None
 
+    target_version = config.get("target_version")
+    if target_version is not None and not isinstance(target_version, list):
+        raise click.BadOptionUsage(
+            "target-version", f"Config key target-version must be a list"
+        )
+
     default_map: Dict[str, Any] = {}
     if ctx.default_map:
         default_map.update(ctx.default_map)
@@ -374,6 +391,11 @@ def target_version_option_callback(
     is_flag=True,
     help="Don't write the files back, just output a diff for each file on stdout.",
 )
+@click.option(
+    "--color/--no-color",
+    is_flag=True,
+    help="Show colored diff. Only applies when `--diff` is given.",
+)
 @click.option(
     "--fast/--safe",
     is_flag=True,
@@ -403,6 +425,14 @@ def target_version_option_callback(
     ),
     show_default=True,
 )
+@click.option(
+    "--force-exclude",
+    type=str,
+    help=(
+        "Like --exclude, but files and directories matching this regex will be "
+        "excluded even when they are passed explicitly as arguments"
+    ),
+)
 @click.option(
     "-q",
     "--quiet",
@@ -452,6 +482,7 @@ def main(
     target_version: List[TargetVersion],
     check: bool,
     diff: bool,
+    color: bool,
     fast: bool,
     pyi: bool,
     py36: bool,
@@ -460,11 +491,12 @@ def main(
     verbose: bool,
     include: str,
     exclude: str,
+    force_exclude: Optional[str],
     src: Tuple[str, ...],
     config: Optional[str],
 ) -> None:
     """The uncompromising code formatter."""
-    write_back = WriteBack.from_configuration(check=check, diff=diff)
+    write_back = WriteBack.from_configuration(check=check, diff=diff, color=color)
     if target_version:
         if py36:
             err("Cannot use both --target-version and --py36")
@@ -491,6 +523,57 @@ def main(
     if code is not None:
         print(format_str(code, mode=mode))
         ctx.exit(0)
+    report = Report(check=check, diff=diff, quiet=quiet, verbose=verbose)
+    sources = get_sources(
+        ctx=ctx,
+        src=src,
+        quiet=quiet,
+        verbose=verbose,
+        include=include,
+        exclude=exclude,
+        force_exclude=force_exclude,
+        report=report,
+    )
+
+    path_empty(
+        sources,
+        "No Python files are present to be formatted. Nothing to do 😴",
+        quiet,
+        verbose,
+        ctx,
+    )
+
+    if len(sources) == 1:
+        reformat_one(
+            src=sources.pop(),
+            fast=fast,
+            write_back=write_back,
+            mode=mode,
+            report=report,
+        )
+    else:
+        reformat_many(
+            sources=sources, fast=fast, write_back=write_back, mode=mode, report=report
+        )
+
+    if verbose or not quiet:
+        out("Oh no! 💥 💔 💥" if report.return_code else "All done! ✨ 🍰 ✨")
+        click.secho(str(report), err=True)
+    ctx.exit(report.return_code)
+
+
+def get_sources(
+    *,
+    ctx: click.Context,
+    src: Tuple[str, ...],
+    quiet: bool,
+    verbose: bool,
+    include: str,
+    exclude: str,
+    force_exclude: Optional[str],
+    report: "Report",
+) -> Set[Path]:
+    """Compute the set of files to be formatted."""
     try:
         include_regex = re_compile_maybe_verbose(include)
     except re.error:
@@ -501,56 +584,56 @@ def main(
     except re.error:
         err(f"Invalid regular expression for exclude given: {exclude!r}")
         ctx.exit(2)
-    report = Report(check=check, diff=diff, quiet=quiet, verbose=verbose)
+    try:
+        force_exclude_regex = (
+            re_compile_maybe_verbose(force_exclude) if force_exclude else None
+        )
+    except re.error:
+        err(f"Invalid regular expression for force_exclude given: {force_exclude!r}")
+        ctx.exit(2)
+
     root = find_project_root(src)
     sources: Set[Path] = set()
-    path_empty(src, quiet, verbose, ctx)
+    path_empty(src, "No Path provided. Nothing to do 😴", quiet, verbose, ctx)
+    exclude_regexes = [exclude_regex]
+    if force_exclude_regex is not None:
+        exclude_regexes.append(force_exclude_regex)
+
     for s in src:
         p = Path(s)
         if p.is_dir():
             sources.update(
-                gen_python_files_in_dir(
-                    p, root, include_regex, exclude_regex, report, get_gitignore(root)
+                gen_python_files(
+                    p.iterdir(),
+                    root,
+                    include_regex,
+                    exclude_regexes,
+                    report,
+                    get_gitignore(root),
                 )
             )
-        elif p.is_file() or s == "-":
-            # if a file was explicitly given, we don't care about its extension
+        elif s == "-":
             sources.add(p)
+        elif p.is_file():
+            sources.update(
+                gen_python_files(
+                    [p], root, None, exclude_regexes, report, get_gitignore(root)
+                )
+            )
         else:
             err(f"invalid path: {s}")
-    if len(sources) == 0:
-        if verbose or not quiet:
-            out("No Python files are present to be formatted. Nothing to do 😴")
-        ctx.exit(0)
-
-    if len(sources) == 1:
-        reformat_one(
-            src=sources.pop(),
-            fast=fast,
-            write_back=write_back,
-            mode=mode,
-            report=report,
-        )
-    else:
-        reformat_many(
-            sources=sources, fast=fast, write_back=write_back, mode=mode, report=report
-        )
-
-    if verbose or not quiet:
-        out("Oh no! 💥 💔 💥" if report.return_code else "All done! ✨ 🍰 ✨")
-        click.secho(str(report), err=True)
-    ctx.exit(report.return_code)
+    return sources
 
 
 def path_empty(
-    src: Tuple[str, ...], quiet: bool, verbose: bool, ctx: click.Context
+    src: Sized, msg: str, quiet: bool, verbose: bool, ctx: click.Context
 ) -> None:
     """
     Exit if there is no `src` provided for formatting
     """
-    if not src:
+    if len(src) == 0:
         if verbose or not quiet:
-            out("No Path provided. Nothing to do 😴")
+            out(msg)
             ctx.exit(0)
 
 
@@ -591,12 +674,21 @@ def reformat_many(
     sources: Set[Path], fast: bool, write_back: WriteBack, mode: Mode, report: "Report"
 ) -> None:
     """Reformat multiple files using a ProcessPoolExecutor."""
+    executor: Executor
     loop = asyncio.get_event_loop()
     worker_count = os.cpu_count()
     if sys.platform == "win32":
         # Work around https://bugs.python.org/issue26903
         worker_count = min(worker_count, 61)
-    executor = ProcessPoolExecutor(max_workers=worker_count)
+    try:
+        executor = ProcessPoolExecutor(max_workers=worker_count)
+    except OSError:
+        # we arrive here if the underlying system does not support multi-processing
+        # like in AWS Lambda, in which case we gracefully fallback to
+        # a ThreadPollExecutor with just a single worker (more workers would not do us
+        # any good due to the Global Interpreter Lock)
+        executor = ThreadPoolExecutor(max_workers=1)
+
     try:
         loop.run_until_complete(
             schedule_formatting(
@@ -611,7 +703,8 @@ def reformat_many(
         )
     finally:
         shutdown(loop)
-        executor.shutdown()
+        if executor is not None:
+            executor.shutdown()
 
 
 async def schedule_formatting(
@@ -712,12 +805,15 @@ def format_file_in_place(
     if write_back == WriteBack.YES:
         with open(src, "w", encoding=encoding, newline=newline) as f:
             f.write(dst_contents)
-    elif write_back == WriteBack.DIFF:
+    elif write_back in (WriteBack.DIFF, WriteBack.COLOR_DIFF):
         now = datetime.utcnow()
         src_name = f"{src}\t{then} +0000"
         dst_name = f"{src}\t{now} +0000"
         diff_contents = diff(src_contents, dst_contents, src_name, dst_name)
 
+        if write_back == write_back.COLOR_DIFF:
+            diff_contents = color_diff(diff_contents)
+
         with lock or nullcontext():
             f = io.TextIOWrapper(
                 sys.stdout.buffer,
@@ -725,12 +821,57 @@ def format_file_in_place(
                 newline=newline,
                 write_through=True,
             )
+            f = wrap_stream_for_windows(f)
             f.write(diff_contents)
             f.detach()
 
     return True
 
 
+def color_diff(contents: str) -> str:
+    """Inject the ANSI color codes to the diff."""
+    lines = contents.split("\n")
+    for i, line in enumerate(lines):
+        if line.startswith("+++") or line.startswith("---"):
+            line = "\033[1;37m" + line + "\033[0m"  # bold white, reset
+        if line.startswith("@@"):
+            line = "\033[36m" + line + "\033[0m"  # cyan, reset
+        if line.startswith("+"):
+            line = "\033[32m" + line + "\033[0m"  # green, reset
+        elif line.startswith("-"):
+            line = "\033[31m" + line + "\033[0m"  # red, reset
+        lines[i] = line
+    return "\n".join(lines)
+
+
+def wrap_stream_for_windows(
+    f: io.TextIOWrapper,
+) -> Union[io.TextIOWrapper, "colorama.AnsiToWin32.AnsiToWin32"]:
+    """
+    Wrap the stream in colorama's wrap_stream so colors are shown on Windows.
+
+    If `colorama` is not found, then no change is made. If `colorama` does
+    exist, then it handles the logic to determine whether or not to change
+    things.
+    """
+    try:
+        from colorama import initialise
+
+        # We set `strip=False` so that we can don't have to modify
+        # test_express_diff_with_color.
+        f = initialise.wrap_stream(
+            f, convert=None, strip=False, autoreset=False, wrap=True
+        )
+
+        # wrap_stream returns a `colorama.AnsiToWin32.AnsiToWin32` object
+        # which does not have a `detach()` method. So we fake one.
+        f.detach = lambda *args, **kwargs: None  # type: ignore
+    except ImportError:
+        pass
+
+    return f
+
+
 def format_stdin_to_stdout(
     fast: bool, *, write_back: WriteBack = WriteBack.NO, mode: Mode
 ) -> bool:
@@ -756,11 +897,15 @@ def format_stdin_to_stdout(
         )
         if write_back == WriteBack.YES:
             f.write(dst)
-        elif write_back == WriteBack.DIFF:
+        elif write_back in (WriteBack.DIFF, WriteBack.COLOR_DIFF):
             now = datetime.utcnow()
             src_name = f"STDIN\t{then} +0000"
             dst_name = f"STDOUT\t{now} +0000"
-            f.write(diff(src, dst, src_name, dst_name))
+            d = diff(src, dst, src_name, dst_name)
+            if write_back == WriteBack.COLOR_DIFF:
+                d = color_diff(d)
+                f = wrap_stream_for_windows(f)
+            f.write(d)
         f.detach()
 
 
@@ -1949,6 +2094,18 @@ class LineGenerator(Visitor[Line]):
             node.insert_child(index, Node(syms.atom, [lpar, operand, rpar]))
         yield from self.visit_default(node)
 
+    def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
+        # Check if it's a docstring
+        if prev_siblings_are(
+            leaf.parent, [None, token.NEWLINE, token.INDENT, syms.simple_stmt]
+        ) and is_multiline_string(leaf):
+            prefix = "    " * self.current_line.depth
+            docstring = fix_docstring(leaf.value[3:-3], prefix)
+            leaf.value = leaf.value[0:3] + docstring + leaf.value[-3:]
+            normalize_string_quotes(leaf)
+
+        yield from self.visit_default(leaf)
+
     def __post_init__(self) -> None:
         """You are in a twisty little maze of passages."""
         v = self.visit_stmt
@@ -2230,6 +2387,22 @@ def preceding_leaf(node: Optional[LN]) -> Optional[Leaf]:
     return None
 
 
+def prev_siblings_are(node: Optional[LN], tokens: List[Optional[NodeType]]) -> bool:
+    """Return if the `node` and its previous siblings match types against the provided
+    list of tokens; the provided `node`has its type matched against the last element in
+    the list.  `None` can be used as the first element to declare that the start of the
+    list is anchored at the start of its parent's children."""
+    if not tokens:
+        return True
+    if tokens[-1] is None:
+        return node is None
+    if not node:
+        return False
+    if node.type != tokens[-1]:
+        return False
+    return prev_siblings_are(node.prev_sibling, tokens[:-1])
+
+
 def child_towards(ancestor: Node, descendant: LN) -> Optional[LN]:
     """Return the child of `ancestor` that contains `descendant`."""
     node: Optional[LN] = descendant
@@ -2510,6 +2683,7 @@ def transform_line(
             is_line_short_enough(line, line_length=line_length, line_str=line_str)
             or line.contains_unsplittable_type_ignore()
         )
+        and not (line.contains_standalone_comments() and line.inside_brackets)
     ):
         # Only apply basic string preprocessing, since lines shouldn't be split here.
         transformers = [string_merge, string_paren_strip]
@@ -5121,7 +5295,7 @@ def generate_ignored_nodes(leaf: Leaf) -> Iterator[LN]:
     """
     container: Optional[LN] = container_of(leaf)
     while container is not None and container.type != token.ENDMARKER:
-        if fmt_on(container):
+        if is_fmt_on(container):
             return
 
         # fix for fmt: on in children
@@ -5135,17 +5309,21 @@ def generate_ignored_nodes(leaf: Leaf) -> Iterator[LN]:
             container = container.next_sibling
 
 
-def fmt_on(container: LN) -> bool:
-    is_fmt_on = False
+def is_fmt_on(container: LN) -> bool:
+    """Determine whether formatting is switched on within a container.
+    Determined by whether the last `# fmt:` comment is `on` or `off`.
+    """
+    fmt_on = False
     for comment in list_comments(container.prefix, is_endmarker=False):
         if comment.value in FMT_ON:
-            is_fmt_on = True
+            fmt_on = True
         elif comment.value in FMT_OFF:
-            is_fmt_on = False
-    return is_fmt_on
+            fmt_on = False
+    return fmt_on
 
 
 def contains_fmt_on_at_column(container: LN, column: int) -> bool:
+    """Determine if children at a given column have formatting switched on."""
     for child in container.children:
         if (
             isinstance(child, Node)
@@ -5153,13 +5331,14 @@ def contains_fmt_on_at_column(container: LN, column: int) -> bool:
             or isinstance(child, Leaf)
             and child.column == column
         ):
-            if fmt_on(child):
+            if is_fmt_on(child):
                 return True
 
     return False
 
 
 def first_leaf_column(node: Node) -> Optional[int]:
+    """Returns the column of the first leaf child of a node."""
     for child in node.children:
         if isinstance(child, Leaf):
             return child.column
@@ -5590,11 +5769,11 @@ def get_gitignore(root: Path) -> PathSpec:
     return PathSpec.from_lines("gitwildmatch", lines)
 
 
-def gen_python_files_in_dir(
-    path: Path,
+def gen_python_files(
+    paths: Iterable[Path],
     root: Path,
-    include: Pattern[str],
-    exclude: Pattern[str],
+    include: Optional[Pattern[str]],
+    exclude_regexes: Iterable[Pattern[str]],
     report: "Report",
     gitignore: PathSpec,
 ) -> Iterator[Path]:
@@ -5606,19 +5785,13 @@ def gen_python_files_in_dir(
     `report` is where output about exclusions goes.
     """
     assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
-    for child in path.iterdir():
-        # First ignore files matching .gitignore
-        if gitignore.match_file(child.as_posix()):
-            report.path_ignored(child, "matches the .gitignore file content")
-            continue
-
+    for child in paths:
         # Then ignore with `exclude` option.
         try:
-            normalized_path = "/" + child.resolve().relative_to(root).as_posix()
+            normalized_path = child.resolve().relative_to(root).as_posix()
         except OSError as e:
             report.path_ignored(child, f"cannot be read because {e}")
             continue
-
         except ValueError:
             if child.is_symlink():
                 report.path_ignored(
@@ -5628,21 +5801,32 @@ def gen_python_files_in_dir(
 
             raise
 
+        # First ignore files matching .gitignore
+        if gitignore.match_file(normalized_path):
+            report.path_ignored(child, "matches the .gitignore file content")
+            continue
+
+        normalized_path = "/" + normalized_path
         if child.is_dir():
             normalized_path += "/"
 
-        exclude_match = exclude.search(normalized_path)
-        if exclude_match and exclude_match.group(0):
-            report.path_ignored(child, "matches the --exclude regular expression")
+        is_excluded = False
+        for exclude in exclude_regexes:
+            exclude_match = exclude.search(normalized_path) if exclude else None
+            if exclude_match and exclude_match.group(0):
+                report.path_ignored(child, "matches the --exclude regular expression")
+                is_excluded = True
+                break
+        if is_excluded:
             continue
 
         if child.is_dir():
-            yield from gen_python_files_in_dir(
-                child, root, include, exclude, report, gitignore
+            yield from gen_python_files(
+                child.iterdir(), root, include, exclude_regexes, report, gitignore
             )
 
         elif child.is_file():
-            include_match = include.search(normalized_path)
+            include_match = include.search(normalized_path) if include else True
             if include_match:
                 yield child
 
@@ -5798,54 +5982,66 @@ def _fixup_ast_constants(
     return node
 
 
-def assert_equivalent(src: str, dst: str) -> None:
-    """Raise AssertionError if `src` and `dst` aren't equivalent."""
-
-    def _v(node: Union[ast.AST, ast3.AST, ast27.AST], depth: int = 0) -> Iterator[str]:
-        """Simple visitor generating strings to compare ASTs by content."""
+def _stringify_ast(
+    node: Union[ast.AST, ast3.AST, ast27.AST], depth: int = 0
+) -> Iterator[str]:
+    """Simple visitor generating strings to compare ASTs by content."""
 
-        node = _fixup_ast_constants(node)
+    node = _fixup_ast_constants(node)
 
-        yield f"{'  ' * depth}{node.__class__.__name__}("
+    yield f"{'  ' * depth}{node.__class__.__name__}("
 
-        for field in sorted(node._fields):  # noqa: F402
-            # TypeIgnore has only one field 'lineno' which breaks this comparison
-            type_ignore_classes = (ast3.TypeIgnore, ast27.TypeIgnore)
-            if sys.version_info >= (3, 8):
-                type_ignore_classes += (ast.TypeIgnore,)
-            if isinstance(node, type_ignore_classes):
-                break
+    for field in sorted(node._fields):  # noqa: F402
+        # TypeIgnore has only one field 'lineno' which breaks this comparison
+        type_ignore_classes = (ast3.TypeIgnore, ast27.TypeIgnore)
+        if sys.version_info >= (3, 8):
+            type_ignore_classes += (ast.TypeIgnore,)
+        if isinstance(node, type_ignore_classes):
+            break
 
-            try:
-                value = getattr(node, field)
-            except AttributeError:
-                continue
+        try:
+            value = getattr(node, field)
+        except AttributeError:
+            continue
 
-            yield f"{'  ' * (depth+1)}{field}="
+        yield f"{'  ' * (depth+1)}{field}="
 
-            if isinstance(value, list):
-                for item in value:
-                    # Ignore nested tuples within del statements, because we may insert
-                    # parentheses and they change the AST.
-                    if (
-                        field == "targets"
-                        and isinstance(node, (ast.Delete, ast3.Delete, ast27.Delete))
-                        and isinstance(item, (ast.Tuple, ast3.Tuple, ast27.Tuple))
-                    ):
-                        for item in item.elts:
-                            yield from _v(item, depth + 2)
+        if isinstance(value, list):
+            for item in value:
+                # Ignore nested tuples within del statements, because we may insert
+                # parentheses and they change the AST.
+                if (
+                    field == "targets"
+                    and isinstance(node, (ast.Delete, ast3.Delete, ast27.Delete))
+                    and isinstance(item, (ast.Tuple, ast3.Tuple, ast27.Tuple))
+                ):
+                    for item in item.elts:
+                        yield from _stringify_ast(item, depth + 2)
 
-                    elif isinstance(item, (ast.AST, ast3.AST, ast27.AST)):
-                        yield from _v(item, depth + 2)
+                elif isinstance(item, (ast.AST, ast3.AST, ast27.AST)):
+                    yield from _stringify_ast(item, depth + 2)
 
-            elif isinstance(value, (ast.AST, ast3.AST, ast27.AST)):
-                yield from _v(value, depth + 2)
+        elif isinstance(value, (ast.AST, ast3.AST, ast27.AST)):
+            yield from _stringify_ast(value, depth + 2)
 
+        else:
+            # Constant strings may be indented across newlines, if they are
+            # docstrings; fold spaces after newlines when comparing
+            if (
+                isinstance(node, ast.Constant)
+                and field == "value"
+                and isinstance(value, str)
+            ):
+                normalized = re.sub(r"\n[ \t]+", "\n ", value)
             else:
-                yield f"{'  ' * (depth+2)}{value!r},  # {value.__class__.__name__}"
+                normalized = value
+            yield f"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}"
 
-        yield f"{'  ' * depth})  # /{node.__class__.__name__}"
+    yield f"{'  ' * depth})  # /{node.__class__.__name__}"
 
+
+def assert_equivalent(src: str, dst: str) -> None:
+    """Raise AssertionError if `src` and `dst` aren't equivalent."""
     try:
         src_ast = parse_ast(src)
     except Exception as exc:
@@ -5864,8 +6060,8 @@ def assert_equivalent(src: str, dst: str) -> None:
             f" 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(_stringify_ast(src_ast))
+    dst_ast_str = "\n".join(_stringify_ast(dst_ast))
     if src_ast_str != dst_ast_str:
         log = dump_to_file(diff(src_ast_str, dst_ast_str, "src", "dst"))
         raise AssertionError(
@@ -6230,5 +6426,32 @@ def patched_main() -> None:
     main()
 
 
+def fix_docstring(docstring: str, prefix: str) -> str:
+    # https://www.python.org/dev/peps/pep-0257/#handling-docstring-indentation
+    if not docstring:
+        return ""
+    # Convert tabs to spaces (following the normal Python rules)
+    # and split into a list of lines:
+    lines = docstring.expandtabs().splitlines()
+    # Determine minimum indentation (first line doesn't count):
+    indent = sys.maxsize
+    for line in lines[1:]:
+        stripped = line.lstrip()
+        if stripped:
+            indent = min(indent, len(line) - len(stripped))
+    # Remove indentation (first line is special):
+    trimmed = [lines[0].strip()]
+    if indent < sys.maxsize:
+        last_line_idx = len(lines) - 2
+        for i, line in enumerate(lines[1:]):
+            stripped_line = line[indent:].rstrip()
+            if stripped_line or i == last_line_idx:
+                trimmed.append(prefix + stripped_line)
+            else:
+                trimmed.append("")
+    # Return a single string:
+    return "\n".join(trimmed)
+
+
 if __name__ == "__main__":
     patched_main()