Fix duplicated labels in TeX output (#11093)

sphinx/writers/latex.py

@@ -1499,7 +1499,26 @@ def add_target(id: str) -> None:
                 pass
             else:
                 add_target(node['refid'])
-        for id in node['ids']:
+        # Temporary fix for https://github.com/sphinx-doc/sphinx/issues/11093
+        # TODO: investigate if a more elegant solution exists (see comments of #11093)
+        if node.get('ismod', False):
+            # Detect if the previous nodes are label targets. If so, remove
+            # the refid thereof from node['ids'] to avoid duplicated ids.
+            def has_dup_label(sib: Element | None) -> bool:
+                return isinstance(sib, nodes.target) and sib.get('refid') in node['ids']
+
+            prev: Element | None = get_prev_node(node)
+            if has_dup_label(prev):
+                ids = node['ids'][:]  # copy to avoid side-effects
+                while has_dup_label(prev):
+                    ids.remove(prev['refid'])
+                    prev = get_prev_node(prev)
+            else:
+                ids = iter(node['ids'])  # read-only iterator
+        else:
+            ids = iter(node['ids'])  # read-only iterator
+
+        for id in ids:
             add_target(id)
 
     def depart_target(self, node: Element) -> None:

tests/roots/test-latex-labels-before-module/automodule1.py

@@ -0,0 +1,2 @@
+"""docstring"""
+

tests/roots/test-latex-labels-before-module/automodule2a.py

@@ -0,0 +1,2 @@
+"""docstring"""
+

tests/roots/test-latex-labels-before-module/automodule2b.py

@@ -0,0 +1,2 @@
+"""docstring"""
+

tests/roots/test-latex-labels-before-module/automodule3.py

@@ -0,0 +1,2 @@
+"""docstring"""
+

tests/roots/test-latex-labels-before-module/conf.py

@@ -0,0 +1,8 @@
+import os
+import sys
+
+sys.path.insert(0, os.path.abspath('.'))
+
+extensions = ['sphinx.ext.autodoc']
+
+nitpicky = True

tests/roots/test-latex-labels-before-module/index.rst

@@ -0,0 +1,48 @@
+latex-labels-before-module
+==========================
+
+.. _label_1a:
+.. _label_1b:
+
+.. module:: module1
+
+   text
+
+.. _label_2:
+
+.. module:: module2a
+
+   text
+
+.. module:: module2b
+
+   text
+
+.. _label_3:
+
+.. module:: module3
+
+   text
+
+.. _label_auto_1a:
+.. _label_auto_1b:
+
+.. automodule:: automodule1
+
+   text
+
+.. _label_auto_2:
+
+.. automodule:: automodule2a
+
+   text
+
+.. automodule:: automodule2b
+
+   text
+
+.. _label_auto_3:
+
+.. automodule:: automodule3
+
+   text

tests/test_build_latex.py

@@ -1708,3 +1708,30 @@ def test_copy_images(app, status, warning):
         'rimg.png',
         'testimäge.png',
     }
+
+
+@pytest.mark.sphinx('latex', testroot='latex-labels-before-module')
+def test_duplicated_labels_before_module(app, status, warning):
+    app.build()
+    content: str = (app.outdir / 'python.tex').read_text()
+
+    def count_label(name):
+        text = r'\phantomsection\label{\detokenize{%s}}' % name
+        return content.count(text)
+
+    pattern = r'\\phantomsection\\label\{\\detokenize\{index:label-(?:auto-)?\d+[a-z]*}}'
+    expect_labels = {match.group() for match in re.finditer(pattern, content)}
+    result_labels = set()
+
+    # iterate over the (explicit) labels in the corresponding index.rst
+    for rst_label_name in {
+        'label_1a', 'label_1b', 'label_2', 'label_3',
+        'label_auto_1a', 'label_auto_1b', 'label_auto_2', 'label_auto_3',
+    }:
+        tex_label_name = 'index:' + rst_label_name.replace('_', '-')
+        tex_label_code = r'\phantomsection\label{\detokenize{%s}}' % tex_label_name
+        assert content.count(tex_label_code) == 1, f'duplicated label: {tex_label_name!r}'
+        result_labels.add(tex_label_code)
+
+    # sort the labels for a better visual diff, if any
+    assert sorted(result_labels) == sorted(expect_labels)