Don't drop comments for cases that are now syntax errors

Author: MichaReiser

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/fstring.py

@@ -285,6 +285,13 @@
          :>0
 
          }"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{x  !s
+         :>0
+         # comment 21
+         }"
 
 x = f"{
     x!s:>{

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/tstring.py

@@ -284,7 +284,12 @@
 # This is interesting. There can be a comment after the format specifier but only if it's
 # on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
 # We'll format is as trailing comments.
-x = t"{
+x = t"{x  !s
+         :>0
+         # comment 21
+         }"
+
+x = f"{
     x!s:>{
         0
         # comment 21
@@ -305,14 +310,14 @@
         """
 
 # Mix of various features.
-t"""{  # comment 26
+t"{  # comment 26
     foo # after foo
    :>{
           x # after x
           }
     # comment 27
     # comment 28
-} woah {x}"""
+} woah {x}"
 
 # Assignment statement
 

crates/ruff_python_formatter/src/comments/placement.rs

@@ -323,18 +323,27 @@ fn handle_enclosed_comment<'a>(
         AnyNodeRef::TString(tstring) => CommentPlacement::dangling(tstring, comment),
         AnyNodeRef::InterpolatedElement(element) => {
             if let Some(preceding) = comment.preceding_node() {
-                // Own line comment before format specifier
-                // ```py
-                // aaaaaaaaaaa = f"""asaaaaaaaaaaaaaaaa {
-                //    aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd
-                //    # comment
-                //    :.3f} cccccccccc"""
-                // ```
-                if comment.line_position().is_own_line()
-                    && element.format_spec.is_some()
-                    && comment.following_node().is_some()
-                {
-                    return CommentPlacement::trailing(preceding, comment);
+                if comment.line_position().is_own_line() && element.format_spec.is_some() {
+                    return if comment.following_node().is_some() {
+                        // Own line comment before format specifier
+                        // ```py
+                        // aaaaaaaaaaa = f"""asaaaaaaaaaaaaaaaa {
+                        //    aaaaaaaaaaaa + bbbbbbbbbbbb + ccccccccccccccc + dddddddd
+                        //    # comment
+                        //    :.3f} cccccccccc"""
+                        // ```
+                        CommentPlacement::trailing(preceding, comment)
+                    } else {
+                        // TODO: This can be removed once format specifiers with a newline are a syntax error.
+                        // This is to handle cases like:
+                        // ```py
+                        // x = f"{x  !s
+                        //          :>0
+                        //          # comment 21
+                        // }"
+                        // ```
+                        CommentPlacement::trailing(element, comment)
+                    };
                 }
             }
 

crates/ruff_python_formatter/src/other/interpolated_string_element.rs

@@ -241,6 +241,7 @@ impl Format<PyFormatContext<'_>> for FormatInterpolatedElement<'_> {
 
                 if conversion.is_none() && format_spec.is_none() {
                     bracket_spacing.fmt(f)?;
+                } else if comments.has_trailing_own_line(self.element) {
                 }
 
                 Ok(())
@@ -258,7 +259,15 @@ impl Format<PyFormatContext<'_>> for FormatInterpolatedElement<'_> {
                 let mut f = WithNodeLevel::new(NodeLevel::ParenthesizedExpression, f);
 
                 if self.context.is_multiline() {
-                    if format_spec.is_none() {
+                    // TODO: The `or comments.has_trailing...` can be removed once newlines in format specs are a syntax error.
+                    // This is to support the following case:
+                    // ```py
+                    // x = f"{x  !s
+                    //          :>0
+                    //          # comment 21
+                    // }"
+                    // ```
+                    if format_spec.is_none() || comments.has_trailing_own_line(self.element) {
                         group(&format_args![
                             open_parenthesis_comments,
                             soft_block_indent(&item)

crates/ruff_python_formatter/tests/snapshots/format@expression__fstring.py.snap

@@ -291,6 +291,13 @@ x = f"{x   =   !  s
          :>0
 
          }"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{x  !s
+         :>0
+         # comment 21
+         }"
 
 x = f"{
     x!s:>{
@@ -1072,6 +1079,13 @@ x = f"aaaaaaaaa { x   = !r}"
 
 # Combine conversion flags with format specifiers
 x = f"{x   =   !s:>0}"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{
+    x!s:>0
+    # comment 21
+}"
 
 x = f"{
     x!s:>{
@@ -1099,9 +1113,10 @@ x = f"""{
 f"{  # comment 26
     foo:>{  # after foo
         x  # after x
-        # comment 27
-        # comment 28
-    }} woah {x}"
+    }
+    # comment 27
+    # comment 28
+} woah {x}"
 
 
 f"""{
@@ -1892,6 +1907,13 @@ x = f"aaaaaaaaa { x   = !r}"
 
 # Combine conversion flags with format specifiers
 x = f"{x   =   !s:>0}"
+# This is interesting. There can be a comment after the format specifier but only if it's
+# on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
+# We'll format is as trailing comments.
+x = f"{
+    x!s:>0
+    # comment 21
+}"
 
 x = f"{
     x!s:>{
@@ -1919,9 +1941,10 @@ x = f"""{
 f"{  # comment 26
     foo:>{  # after foo
         x  # after x
-        # comment 27
-        # comment 28
-    }} woah {x}"
+    }
+    # comment 27
+    # comment 28
+} woah {x}"
 
 
 f"""{

crates/ruff_python_formatter/tests/snapshots/format@expression__tstring.py.snap

@@ -290,7 +290,12 @@ x = t"{x   =   !  s
 # This is interesting. There can be a comment after the format specifier but only if it's
 # on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
 # We'll format is as trailing comments.
-x = t"{
+x = t"{x  !s
+         :>0
+         # comment 21
+         }"
+
+x = f"{
     x!s:>{
         0
         # comment 21
@@ -311,14 +316,14 @@ x = t"""{"foo " +    # comment 24
         """
 
 # Mix of various features.
-t"""{  # comment 26
+t"{  # comment 26
     foo # after foo
    :>{
           x # after x
           }
     # comment 27
     # comment 28
-} woah {x}"""
+} woah {x}"
 
 # Assignment statement
 
@@ -1052,6 +1057,11 @@ x = t"{x   =   !s:>0}"
 # on it's own line. Refer to https://github.com/astral-sh/ruff/pull/7787 for more details.
 # We'll format is as trailing comments.
 x = t"{
+    x!s:>0
+    # comment 21
+}"
+
+x = f"{
     x!s:>{
         0
         # comment 21
@@ -1073,13 +1083,13 @@ x = t"""{
         """
 
 # Mix of various features.
-t"""{  # comment 26
+t"{  # comment 26
     foo:>{  # after foo
         x  # after x
     }
     # comment 27
     # comment 28
-} woah {x}"""
+} woah {x}"
 
 # Assignment statement
 

crates/ty_python_semantic/src/python_platform.rs

@@ -1,12 +1,10 @@
 use std::fmt::{Display, Formatter};
 
-use ruff_macros::RustDoc;
-
 /// The target platform to assume when resolving types.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[cfg_attr(
     feature = "serde",
-    derive(serde::Serialize, serde::Deserialize, RustDoc),
+    derive(serde::Serialize, serde::Deserialize, ruff_macros::RustDoc),
     serde(rename_all = "kebab-case")
 )]
 pub enum PythonPlatform {