Format the comment content (#4786)

crates/ruff_python_formatter/src/comments/format.rs

@@ -1,9 +1,11 @@
+use crate::comments::SourceComment;
 use crate::context::NodeLevel;
 use crate::prelude::*;
 use crate::trivia::{lines_after, lines_before};
-use ruff_formatter::{format_args, write};
+use ruff_formatter::{format_args, write, FormatError, SourceCode};
 use ruff_python_ast::node::AnyNodeRef;
 use ruff_python_ast::prelude::AstNode;
+use ruff_text_size::{TextLen, TextRange, TextSize};
 
 /// Formats the leading comments of a node.
 pub(crate) fn leading_comments<T>(node: &T) -> FormatLeadingComments
@@ -30,10 +32,7 @@ impl Format<PyFormatContext<'_>> for FormatLeadingComments<'_> {
             let lines_after_comment = lines_after(f.context().contents(), slice.end());
             write!(
                 f,
-                [
-                    source_text_slice(slice.range(), ContainsNewlines::No),
-                    empty_lines(lines_after_comment)
-                ]
+                [format_comment(comment), empty_lines(lines_after_comment)]
             )?;
 
             comment.mark_formatted();
@@ -64,7 +63,6 @@ impl Format<PyFormatContext<'_>> for FormatTrailingComments<'_> {
 
         for trailing in comments.trailing_comments(self.node) {
             let slice = trailing.slice();
-            let content = source_text_slice(slice.range(), ContainsNewlines::No);
 
             let lines_before_comment = lines_before(f.context().contents(), slice.start());
             has_empty_lines_before |= lines_before_comment > 0;
@@ -81,7 +79,10 @@ impl Format<PyFormatContext<'_>> for FormatTrailingComments<'_> {
                     f,
                     [
                         line_suffix(&format_with(|f| {
-                            write!(f, [empty_lines(lines_before_comment), content])
+                            write!(
+                                f,
+                                [empty_lines(lines_before_comment), format_comment(trailing)]
+                            )
                         })),
                         expand_parent()
                     ]
@@ -90,7 +91,7 @@ impl Format<PyFormatContext<'_>> for FormatTrailingComments<'_> {
                 write!(
                     f,
                     [
-                        line_suffix(&format_args![space(), space(), content]),
+                        line_suffix(&format_args![space(), space(), format_comment(trailing)]),
                         expand_parent()
                     ]
                 )?;
@@ -132,7 +133,7 @@ impl Format<PyFormatContext<'_>> for FormatDanglingComments<'_> {
             write!(
                 f,
                 [
-                    source_text_slice(comment.slice().range(), ContainsNewlines::No),
+                    format_comment(comment),
                     empty_lines(lines_after(f.context().contents(), comment.slice().end()))
                 ]
             )?;
@@ -146,6 +147,66 @@ impl Format<PyFormatContext<'_>> for FormatDanglingComments<'_> {
     }
 }
 
+/// Formats the content of the passed comment.
+///
+/// * Adds a whitespace between `#` and the comment text except if the first character is a `#`, `:`, `'`, or `!`
+/// * Replaces non breaking whitespaces with regular whitespaces except if in front of a `types:` comment
+const fn format_comment(comment: &SourceComment) -> FormatComment {
+    FormatComment { comment }
+}
+
+struct FormatComment<'a> {
+    comment: &'a SourceComment,
+}
+
+impl Format<PyFormatContext<'_>> for FormatComment<'_> {
+    fn fmt(&self, f: &mut Formatter<PyFormatContext<'_>>) -> FormatResult<()> {
+        let slice = self.comment.slice();
+        let comment_text = slice.text(SourceCode::new(f.context().contents()));
+
+        let trimmed = comment_text.trim_end();
+        let trailing_whitespace_len = comment_text.text_len() - trimmed.text_len();
+
+        let Some(content) = trimmed.strip_prefix('#') else {
+            return Err(FormatError::SyntaxError);
+        };
+
+        // Fast path for correctly formatted comments:
+        // * Start with a `#` and are followed by a space
+        // * Have no trailing whitespace.
+        if trailing_whitespace_len == TextSize::new(0) && content.starts_with(' ') {
+            return source_text_slice(slice.range(), ContainsNewlines::No).fmt(f);
+        }
+
+        write!(f, [source_position(slice.start()), text("#")])?;
+
+        // Starts with a non breaking space
+        let start_offset =
+            if content.starts_with('\u{A0}') && !content.trim_start().starts_with("type:") {
+                // Replace non-breaking space with a space (if not followed by a normal space)
+                "#\u{A0}".text_len()
+            } else {
+                '#'.text_len()
+            };
+
+        // Add a space between the `#` and the text if the source contains none.
+        if !content.is_empty() && !content.starts_with([' ', '!', ':', '#', '\'']) {
+            write!(f, [space()])?;
+        }
+
+        let start = slice.start() + start_offset;
+        let end = slice.range().end() - trailing_whitespace_len;
+
+        write!(
+            f,
+            [
+                source_text_slice(TextRange::new(start, end), ContainsNewlines::No),
+                source_position(slice.end())
+            ]
+        )
+    }
+}
+
 // Helper that inserts the appropriate number of empty lines before a comment, depending on the node level.
 // Top level: Up to two empty lines
 // parenthesized: A single empty line

crates/ruff_python_formatter/src/snapshots/ruff_python_formatter__tests__black_test__comments2_py.snap

@@ -349,7 +349,7 @@ instruction()#comment with bad spacing
          # yup
          for element in collection.select_elements()
          # right
-@@ -140,34 +132,26 @@
+@@ -140,28 +132,20 @@
              # and round and round we go
          # and round and round we go
  
@@ -386,13 +386,6 @@ instruction()#comment with bad spacing
  #######################
  ### SECTION COMMENT ###
  #######################
- 
- 
--instruction()  # comment with bad spacing
-+instruction()  #comment with bad spacing
- 
- # END COMMENTS
- # MORE END COMMENTS
 ```
 
 ## Ruff Output
@@ -551,7 +544,7 @@ class Test:
 #######################
 
 
-instruction()  #comment with bad spacing
+instruction()  # comment with bad spacing
 
 # END COMMENTS
 # MORE END COMMENTS

crates/ruff_python_formatter/src/snapshots/ruff_python_formatter__tests__black_test__comments8_py.snap

@@ -1,53 +0,0 @@
----
-source: crates/ruff_python_formatter/src/lib.rs
-expression: snapshot
-input_file: crates/ruff_python_formatter/resources/test/fixtures/black/simple_cases/comments8.py
----
-## Input
-
-```py
-# The percent-percent comments are Spyder IDE cells.
-# Both `#%%`` and `# %%` are accepted, so `black` standardises
-# to the latter.
-
-#%%
-# %%
-```
-
-## Black Differences
-
-```diff
---- Black
-+++ Ruff
-@@ -2,5 +2,5 @@
- # Both `#%%`` and `# %%` are accepted, so `black` standardises
- # to the latter.
- 
--# %%
-+#%%
- # %%
-```
-
-## Ruff Output
-
-```py
-# The percent-percent comments are Spyder IDE cells.
-# Both `#%%`` and `# %%` are accepted, so `black` standardises
-# to the latter.
-
-#%%
-# %%
-```
-
-## Black Output
-
-```py
-# The percent-percent comments are Spyder IDE cells.
-# Both `#%%`` and `# %%` are accepted, so `black` standardises
-# to the latter.
-
-# %%
-# %%
-```
-
-

crates/ruff_python_formatter/src/snapshots/ruff_python_formatter__tests__black_test__comments_non_breaking_space_py.snap

@@ -42,23 +42,19 @@ def function(a:int=42):
 +    # DEFAULT_TYPE_ATTRIBUTES,
  )
 -
--result = 1  # A simple comment
+ result = 1  # A simple comment
 -result = (1,)  # Another one
 -
--result = 1  #  type: ignore
--result = 1  # This comment is talking about type: ignore
--square = Square(4)  #  type: Optional[Square]
++result = (    1, )  # Another one
+ result = 1  #  type: ignore
+ result = 1  # This comment is talking about type: ignore
+ square = Square(4)  #  type: Optional[Square]
 -
 -
 -def function(a: int = 42):
 -    """This docstring is already formatted
 -    a
 -    b
-+result = 1  # A simple comment
-+result = (    1, )  # Another one
-+result = 1  # type: ignore
-+result = 1  # This comment is talking about type: ignore
-+square = Square(4)  # type: Optional[Square]
 +def function(a:int=42):
 +    """ This docstring is already formatted
 +       a
@@ -76,11 +72,11 @@ def function(a:int=42):
 from .config import (  ConfigTypeAttributes,    Int,    Path,    # String,
     # DEFAULT_TYPE_ATTRIBUTES,
 )
-result = 1  # A simple comment
-result = (    1, )  # Another one
-result = 1  # type: ignore
-result = 1  # This comment is talking about type: ignore
-square = Square(4)  # type: Optional[Square]
+result = 1  # A simple comment
+result = (    1, )  # Another one
+result = 1  #  type: ignore
+result = 1  # This comment is talking about type: ignore
+square = Square(4)  #  type: Optional[Square]
 def function(a:int=42):
     """ This docstring is already formatted
        a

crates/ruff_python_formatter/src/snapshots/ruff_python_formatter__tests__black_test__fmtskip7_py.snap

@@ -19,22 +19,19 @@ d = "thisisasuperlongstringthisisasuperlongstringthisisasuperlongstringthisisasu
 +++ Ruff
 @@ -1,4 +1,4 @@
 -a = "this is some code"
--b =     5  # fmt:skip
--c = 9  # fmt: skip
--d = "thisisasuperlongstringthisisasuperlongstringthisisasuperlongstringthisisasuperlongstring"  # fmt:skip
 +a =     "this is some code"
-+b =     5  #fmt:skip
-+c = 9  #fmt: skip
-+d = "thisisasuperlongstringthisisasuperlongstringthisisasuperlongstringthisisasuperlongstring"  #fmt:skip
+ b =     5  # fmt:skip
+ c = 9  # fmt: skip
+ d = "thisisasuperlongstringthisisasuperlongstringthisisasuperlongstringthisisasuperlongstring"  # fmt:skip
 ```
 
 ## Ruff Output
 
 ```py
 a =     "this is some code"
-b =     5  #fmt:skip
-c = 9  #fmt: skip
-d = "thisisasuperlongstringthisisasuperlongstringthisisasuperlongstringthisisasuperlongstring"  #fmt:skip
+b =     5  # fmt:skip
+c = 9  # fmt: skip
+d = "thisisasuperlongstringthisisasuperlongstringthisisasuperlongstringthisisasuperlongstring"  # fmt:skip
 ```
 
 ## Black Output