Add formatting of type parameters in class and function definitions (#6161)

Part of #5062 
Closes https://github.com/astral-sh/ruff/issues/5931

Implements formatting of a sequence of type parameters in a dedicated
struct for reuse by classes, functions, and type aliases (preparing for
#5929). Adds formatting of type parameters in class and function
definitions — previously, they were just elided.

crates/ruff_python_formatter/tests/snapshots/black_compatibility@py_312__type_params.py.snap

@@ -1,159 +0,0 @@
----
-source: crates/ruff_python_formatter/tests/fixtures.rs
-input_file: crates/ruff_python_formatter/resources/test/fixtures/black/py_312/type_params.py
----
-## Input
-
-```py
-def func  [T ](): pass
-async def func [ T ] (): pass
-class C[ T ] : pass
-
-def all_in[T   :   int,U : (bytes, str),*   Ts,**P](): pass
-
-def really_long[WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine](): pass
-
-def even_longer[WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine: WhatIfItHadABound](): pass
-
-def it_gets_worse[WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine, ItCouldBeGenericOverMultipleTypeVars](): pass
-
-def magic[Trailing, Comma,](): pass
-```
-
-## Black Differences
-
-```diff
---- Black
-+++ Ruff
-@@ -1,40 +1,30 @@
--def func[T]():
-+def func():
-     pass
- 
- 
--async def func[T]():
-+async def func():
-     pass
- 
- 
--class C[T]:
-+class C:
-     pass
- 
- 
--def all_in[T: int, U: (bytes, str), *Ts, **P]():
-+def all_in():
-     pass
- 
- 
--def really_long[
--    WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine
--]():
-+def really_long():
-     pass
- 
- 
--def even_longer[
--    WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine: WhatIfItHadABound
--]():
-+def even_longer():
-     pass
- 
- 
--def it_gets_worse[
--    WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine,
--    ItCouldBeGenericOverMultipleTypeVars,
--]():
-+def it_gets_worse():
-     pass
- 
- 
--def magic[
--    Trailing,
--    Comma,
--]():
-+def magic():
-     pass
-```
-
-## Ruff Output
-
-```py
-def func():
-    pass
-
-
-async def func():
-    pass
-
-
-class C:
-    pass
-
-
-def all_in():
-    pass
-
-
-def really_long():
-    pass
-
-
-def even_longer():
-    pass
-
-
-def it_gets_worse():
-    pass
-
-
-def magic():
-    pass
-```
-
-## Black Output
-
-```py
-def func[T]():
-    pass
-
-
-async def func[T]():
-    pass
-
-
-class C[T]:
-    pass
-
-
-def all_in[T: int, U: (bytes, str), *Ts, **P]():
-    pass
-
-
-def really_long[
-    WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine
-]():
-    pass
-
-
-def even_longer[
-    WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine: WhatIfItHadABound
-]():
-    pass
-
-
-def it_gets_worse[
-    WhatIsTheLongestTypeVarNameYouCanThinkOfEnoughToMakeBlackSplitThisLine,
-    ItCouldBeGenericOverMultipleTypeVars,
-]():
-    pass
-
-
-def magic[
-    Trailing,
-    Comma,
-]():
-    pass
-```
-
-

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

@@ -27,6 +27,17 @@ b3 = [
     aksjdhflsakhdflkjsadlfajkslhfdkjsaldajlahflashdfljahlfksajlhfajfjfsaahflakjslhdfkjalhdskjfa,
     aksjdhflsakhdflkjsadlfajkslhfdkjsaldajlahflashdfljahlfksajlhfajfjfsaahflakjslhdfkjalhdskjfa
 ]
+
+# Comment placement in non-empty lists
+c1 = [ # trailing open bracket
+    # leading item
+    1,
+
+    # between
+
+    2, # trailing item
+    # leading close bracket
+] # trailing close bracket
 ```
 
 ## Output
@@ -53,6 +64,16 @@ b3 = [
     aksjdhflsakhdflkjsadlfajkslhfdkjsaldajlahflashdfljahlfksajlhfajfjfsaahflakjslhdfkjalhdskjfa,
     aksjdhflsakhdflkjsadlfajkslhfdkjsaldajlahflashdfljahlfksajlhfajfjfsaahflakjslhdfkjalhdskjfa,
 ]
+
+# Comment placement in non-empty lists
+c1 = [
+    # trailing open bracket
+    # leading item
+    1,
+    # between
+    2,  # trailing item
+    # leading close bracket
+]  # trailing close bracket
 ```
 
 

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

@@ -49,6 +49,14 @@ class TestTrailingComment2: # trailing comment
     pass
 
 
+class TestTrailingComment3[T]: # trailing comment
+    pass
+
+
+class TestTrailingComment4[T](A): # trailing comment
+    pass
+
+
 class Test:
     """Docstring"""
 
@@ -150,6 +158,60 @@ class AltCLIPOutput(
     # Copied from transformers.models.clip.modeling_clip.CLIPOutput with CLIP->AltCLIP
 ):
     ...
+
+
+class TestTypeParams[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, Cccccccccccccccccccccc]:
+    pass
+
+
+class TestTypeParams[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa, *Bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, **Cccccccccccccccccccccc]:
+    pass
+
+
+class TestTypeParams[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]:
+    pass
+
+
+class TestTypeParams[*Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]:
+    pass
+
+
+class TestTypeParams[**Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]:
+    pass
+
+
+class TestTypeParams[**P, *Ts, T]:
+    pass
+
+
+class TestTypeParams[ # trailing bracket comment
+    # leading comment
+    A,
+
+    # in between comment
+
+    B,
+    # another leading comment
+    C,
+    D, # trailing comment
+    # leading bracket comment
+]:
+    pass
+
+
+
+class TestTypeParams[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa](B, C, D):
+    pass
+
+
+
+class TestTypeParams[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa](Bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb, Cccccccccccccccccccccccc, Ddddddddddddddddddddddddd):
+    pass
+
+
+
+class TestTypeParams[A, B, C](meta=Aaaaaaaaaaaaaaaaaaaaaa):
+    pass
 ```
 
 ## Output
@@ -216,6 +278,14 @@ class TestTrailingComment2:  # trailing comment
     pass
 
 
+class TestTrailingComment3[T]:  # trailing comment
+    pass
+
+
+class TestTrailingComment4[T](A):  # trailing comment
+    pass
+
+
 class Test:
     """Docstring"""
 
@@ -318,6 +388,77 @@ class AltCLIPOutput(
     # Copied from transformers.models.clip.modeling_clip.CLIPOutput with CLIP->AltCLIP
 ):
     ...
+
+
+class TestTypeParams[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    Bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    Cccccccccccccccccccccc,
+]:
+    pass
+
+
+class TestTypeParams[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    *Bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    **Cccccccccccccccccccccc,
+]:
+    pass
+
+
+class TestTypeParams[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+]:
+    pass
+
+
+class TestTypeParams[
+    *Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+]:
+    pass
+
+
+class TestTypeParams[
+    **Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+]:
+    pass
+
+
+class TestTypeParams[**P, *Ts, T]:
+    pass
+
+
+class TestTypeParams[  # trailing bracket comment
+    # leading comment
+    A,
+    # in between comment
+    B,
+    # another leading comment
+    C,
+    D,  # trailing comment
+    # leading bracket comment
+]:
+    pass
+
+
+class TestTypeParams[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+](B, C, D):
+    pass
+
+
+class TestTypeParams[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+](
+    Bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb,
+    Cccccccccccccccccccccccc,
+    Ddddddddddddddddddddddddd,
+):
+    pass
+
+
+class TestTypeParams[A, B, C](meta=Aaaaaaaaaaaaaaaaaaaaaa):
+    pass
 ```
 
 

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

@@ -72,6 +72,52 @@ def argument_with_long_type_annotation(
 
 def test(): ...
 
+# Type parameter empty line spacing
+def test[
+    # comment
+    A,
+
+    # another
+
+    B,
+](): ...
+
+
+# Type parameter comments
+def type_param_comments[ # trailing bracket comment
+    # leading comment
+    A,
+
+    # in between comment
+
+    B,
+    # another leading comment
+    C,
+    D, # trailing comment
+    # leading bracket comment
+]():
+    # body comment
+    pass
+
+
+# Note empty type parameters is not valid syntax, e.g.
+# def test[](): ...
+
+
+# Different type parameter wrappings
+
+def single_line[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbb, Ccccccccccccccccc]():
+    pass
+
+def params_on_their_own_line[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbb, Ccccccccccc, Ddddddddddddd, Eeeeeeee]():
+    pass
+
+def param_per_line[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbb, Ccccccccccccccccc, Ddddddddddddd, Eeeeeeeeeeeeeeeee, ffffffffffff]():
+    pass
+
+def single_line_trailing_comma[A, B, C,]():
+    pass
+
 # Comment
 def with_leading_comment(): ...
 
@@ -353,6 +399,70 @@ def test():
     ...
 
 
+# Type parameter empty line spacing
+def test[
+    # comment
+    A,
+    # another
+    B,
+]():
+    ...
+
+
+# Type parameter comments
+def type_param_comments[  # trailing bracket comment
+    # leading comment
+    A,
+    # in between comment
+    B,
+    # another leading comment
+    C,
+    D,  # trailing comment
+    # leading bracket comment
+]():
+    # body comment
+    pass
+
+
+# Note empty type parameters is not valid syntax, e.g.
+# def test[](): ...
+
+
+# Different type parameter wrappings
+
+def single_line[Aaaaaaaaaaaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbb, Ccccccccccccccccc]():
+    pass
+
+
+def params_on_their_own_line[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    Bbbbbbbbbbbbbbb,
+    Ccccccccccc,
+    Ddddddddddddd,
+    Eeeeeeee,
+]():
+    pass
+
+
+def param_per_line[
+    Aaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
+    Bbbbbbbbbbbbbbb,
+    Ccccccccccccccccc,
+    Ddddddddddddd,
+    Eeeeeeeeeeeeeeeee,
+    ffffffffffff,
+]():
+    pass
+
+
+def single_line_trailing_comma[
+    A,
+    B,
+    C,
+]():
+    pass
+
+
 # Comment
 def with_leading_comment():
     ...