Don't split on for-loop variable unpacks

[etc/vim.git] / black.py

diff --git a/black.py b/black.py
index d48fddbe6526d6dc2753a71c482e53afe8c2f9ee..774d91dc2a7f64ec2dbc252a55e0fe051d5c429c 100644 (file)
--- a/black.py
+++ b/black.py
@@ -55,6 +55,15 @@ class CannotSplit(Exception):
     help='How many character per line to allow.',
     show_default=True,
 )
+@click.option(
+    '--check',
+    is_flag=True,
+    help=(
+        "Don't write back the files, just return the status.  Return code 0 "
+        "means nothing changed.  Return code 1 means some files were "
+        "reformatted.  Return code 123 means there was an internal error."
+    ),
+)
 @click.option(
     '--fast/--safe',
     is_flag=True,
@@ -67,7 +76,9 @@ class CannotSplit(Exception):
     type=click.Path(exists=True, file_okay=True, dir_okay=True, readable=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, fast: bool, src: List[str]
+) -> None:
     """The uncompromising code formatter."""
     sources: List[Path] = []
     for s in src:
@@ -85,7 +96,9 @@ def main(ctx: click.Context, line_length: int, fast: bool, src: List[str]) -> No
         p = sources[0]
         report = Report()
         try:
-            changed = format_file_in_place(p, line_length=line_length, fast=fast)
+            changed = format_file_in_place(
+                p, line_length=line_length, fast=fast, write_back=not check
+            )
             report.done(p, changed)
         except Exception as exc:
             report.failed(p, str(exc))
@@ -96,7 +109,9 @@ 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, not check, fast, loop, executor
+                )
             )
         finally:
             loop.close()
@@ -106,13 +121,14 @@ def main(ctx: click.Context, line_length: int, fast: bool, src: List[str]) -> No
 async def schedule_formatting(
     sources: List[Path],
     line_length: int,
+    write_back: bool,
     fast: bool,
     loop: BaseEventLoop,
     executor: Executor,
 ) -> int:
     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
         )
         for src in sources
     }
@@ -135,15 +151,18 @@ async def schedule_formatting(
     return report.return_code
 
 
-def format_file_in_place(src: Path, line_length: int, fast: bool) -> bool:
+def format_file_in_place(
+    src: Path, line_length: int, fast: bool, write_back: bool = False
+) -> bool:
     """Format the file and rewrite if changed. Return True if changed."""
     try:
         contents, encoding = format_file(src, line_length=line_length, fast=fast)
     except NothingChanged:
         return False
 
-    with open(src, "w", encoding=encoding) as f:
-        f.write(contents)
+    if write_back:
+        with open(src, "w", encoding=encoding) as f:
+            f.write(contents)
     return True
 
 
@@ -373,6 +392,8 @@ class Line:
     comments: Dict[LeafID, Leaf] = attrib(default=Factory(dict))
     bracket_tracker: BracketTracker = attrib(default=Factory(BracketTracker))
     inside_brackets: bool = attrib(default=False)
+    has_for: bool = attrib(default=False)
+    _for_loop_variable: bool = attrib(default=False, init=False)
 
     def append(self, leaf: Leaf, preformatted: bool = False) -> None:
         has_value = leaf.value.strip()
@@ -384,8 +405,10 @@ 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)
+            self.maybe_increment_for_loop_variable(leaf)
             if self.maybe_adapt_standalone_comment(leaf):
                 return
 
@@ -489,6 +512,29 @@ class Line:
 
         return False
 
+    def maybe_increment_for_loop_variable(self, leaf: Leaf) -> bool:
+        """In a for loop, or comprehension, the variables are often unpacks.
+
+        To avoid splitting on the comma in this situation, we will increase
+        the depth of tokens between `for` and `in`.
+        """
+        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
+
+    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 maybe_adapt_standalone_comment(self, comment: Leaf) -> bool:
         """Hack a standalone comment to act as a trailing comment for line splitting.
 
@@ -1321,7 +1367,15 @@ class Report:
     @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
+        # 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:
+            return 1
+
+        return 0
 
     def __str__(self) -> str:
         """A color report of the current state.