Fix PEP 695 output for classes in the LaTeX builder (#12561)

CHANGES.rst

@@ -160,6 +160,8 @@ Bugs fixed
   Patch by Jakob Lykke Andersen and Adam Turner.
 * #11041: linkcheck: Ignore URLs that respond with non-Unicode content.
   Patch by James Addison.
+* #12543: Fix :pep:`695` formatting for LaTeX output.
+  Patch by Bénédikt Tran.
 
 Testing
 -------

sphinx/writers/latex.py

@@ -724,19 +724,21 @@ class LaTeXTranslator(SphinxTranslator):
             return e.get('multi_line_parameter_list')
 
         self.has_tp_list = False
+        self.orphan_tp_list = False
 
         for child in node:
             if isinstance(child, addnodes.desc_type_parameter_list):
                 self.has_tp_list = True
-                # recall that return annotations must follow an argument list,
-                # so signatures of the form "foo[tp_list] -> retann" will not
-                # be encountered (if they should, the `domains.python.py_sig_re`
-                # pattern must be modified accordingly)
-                arglist = next_sibling(child)
-                assert isinstance(arglist, addnodes.desc_parameterlist)
-                # tp_list + arglist: \macro{name}{tp_list}{arglist}{return}
                 multi_tp_list = has_multi_line(child)
+                arglist = next_sibling(child)
+                if isinstance(arglist, addnodes.desc_parameterlist):
+                    # tp_list + arglist: \macro{name}{tp_list}{arglist}{retann}
                     multi_arglist = has_multi_line(arglist)
+                else:
+                    # orphan tp_list:    \macro{name}{tp_list}{}{retann}
+                    # see: https://github.com/sphinx-doc/sphinx/issues/12543
+                    self.orphan_tp_list = True
+                    multi_arglist = False
 
                 if multi_tp_list:
                     if multi_arglist:
@@ -751,7 +753,7 @@ class LaTeXTranslator(SphinxTranslator):
                 break
 
             if isinstance(child, addnodes.desc_parameterlist):
-                # arglist only: \macro{name}{arglist}{return}
+                # arglist only: \macro{name}{arglist}{retann}
                 if has_multi_line(child):
                     self.body.append(CR + r'\pysigwithonelineperarg{')
                 else:
@@ -857,7 +859,13 @@ class LaTeXTranslator(SphinxTranslator):
         self.multi_line_parameter_list = node.get('multi_line_parameter_list', False)
 
     def visit_desc_parameterlist(self, node: Element) -> None:
-        if not self.has_tp_list:
+        if self.has_tp_list:
+            if self.orphan_tp_list:
+                # close type parameters list (#2)
+                self.body.append('}{')
+                # empty parameters list argument (#3)
+                return
+        else:
             # close name argument (#1), open parameters list argument (#2)
             self.body.append('}{')
         self._visit_sig_parameter_list(node, addnodes.desc_parameter)

tests/roots/test-domain-py-python_maximum_signature_line_length/index.rst

@@ -4,3 +4,16 @@ domain-py-maximum_signature_line_length
 .. py:function:: hello(name: str) -> str
 
 .. py:function:: foo([a, [b, ]]c, d[, e, f])
+
+.. py:function:: generic_arg[T]
+
+.. py:function:: generic_foo[T]()
+
+.. py:function:: generic_bar[T](x: list[T])
+
+.. py:function:: generic_ret[R]() -> R
+
+.. py:class:: MyGenericClass[X]
+
+.. py:class:: MyList[T](list[T])
+

tests/test_builders/test_build_html.py

@@ -376,3 +376,34 @@ def test_html_remove_sources_before_write_gh_issue_10786(app, warning):
 
     file = os.fsdecode(target)
     assert f'WARNING: cannot copy image file {file!r}: {file!s} does not exist' == ws[-1]
+
+
+@pytest.mark.sphinx('html', testroot='domain-py-python_maximum_signature_line_length',
+                    confoverrides={'python_maximum_signature_line_length': 1})
+def test_html_pep_695_one_type_per_line(app, cached_etree_parse):
+    app.build()
+    fname = app.outdir / 'index.html'
+    etree = cached_etree_parse(fname)
+
+    class chk:
+        def __init__(self, expect):
+            self.expect = expect
+
+        def __call__(self, nodes):
+            assert len(nodes) == 1, nodes
+            objnode = ''.join(nodes[0].itertext()).replace('\n\n', '')
+            objnode = objnode.rstrip(chr(182))  # remove '¶' symbol
+            objnode = objnode.strip('\n')  # remove surrounding new lines
+            assert objnode == self.expect
+
+    # each signature has a dangling ',' at the end of its parameters lists
+    check_xpath(etree, fname, r'.//dt[@id="generic_foo"][1]',
+                chk('generic_foo[\nT,\n]()'))
+    check_xpath(etree, fname, r'.//dt[@id="generic_bar"][1]',
+                chk('generic_bar[\nT,\n](\nx: list[T],\n)'))
+    check_xpath(etree, fname, r'.//dt[@id="generic_ret"][1]',
+                chk('generic_ret[\nR,\n]() → R'))
+    check_xpath(etree, fname, r'.//dt[@id="MyGenericClass"][1]',
+                chk('class MyGenericClass[\nX,\n]'))
+    check_xpath(etree, fname, r'.//dt[@id="MyList"][1]',
+                chk('class MyList[\nT,\n](list[T])'))

tests/test_builders/test_build_latex.py

@@ -1760,6 +1760,28 @@ def test_one_parameter_per_line(app, status, warning):
 
     assert ('\\pysigwithonelineperarg{\\sphinxbfcode{\\sphinxupquote{foo}}}' in result)
 
+    # generic_arg[T]
+    assert ('\\pysiglinewithargsretwithtypelist{\\sphinxbfcode{\\sphinxupquote{generic\\_arg}}}'
+            '{\\sphinxtypeparam{\\DUrole{n}{T}}}{}{}' in result)
+
+    # generic_foo[T]()
+    assert ('\\pysiglinewithargsretwithtypelist{\\sphinxbfcode{\\sphinxupquote{generic\\_foo}}}' in result)
+
+    # generic_bar[T](x: list[T])
+    assert ('\\pysigwithonelineperargwithtypelist{\\sphinxbfcode{\\sphinxupquote{generic\\_bar}}}' in result)
+
+    # generic_ret[R]() -> R
+    assert ('\\pysiglinewithargsretwithtypelist{\\sphinxbfcode{\\sphinxupquote{generic\\_ret}}}'
+            '{\\sphinxtypeparam{\\DUrole{n}{R}}}{}{{ $\\rightarrow$ R}}' in result)
+
+    # MyGenericClass[X]
+    assert ('\\pysiglinewithargsretwithtypelist{\\sphinxbfcode{\\sphinxupquote{class\\DUrole{w}{ '
+            '}}}\\sphinxbfcode{\\sphinxupquote{MyGenericClass}}}' in result)
+
+    # MyList[T](list[T])
+    assert ('\\pysiglinewithargsretwithtypelist{\\sphinxbfcode{\\sphinxupquote{class\\DUrole{w}{ '
+            '}}}\\sphinxbfcode{\\sphinxupquote{MyList}}}' in result)
+
 
 @pytest.mark.sphinx('latex', testroot='markup-rubric')
 def test_latex_rubric(app):

tests/test_domains/test_domain_py.py

@@ -753,7 +753,7 @@ def test_function_pep_695(app):
         S,\
         T: int,\
         U: (int, str),\
-        R: int | int,\
+        R: int | str,\
         A: int | Annotated[int, ctype("char")],\
         *V,\
         **P\
@@ -795,7 +795,7 @@ def test_function_pep_695(app):
                             desc_sig_space,
                             [desc_sig_punctuation, '|'],
                             desc_sig_space,
-                            [pending_xref, 'int'],
+                            [pending_xref, 'str'],
                         )],
                     )],
                     [desc_type_parameter, (