Fix the MoveModuleTargets transform (#11647)

This resolves a regression introduced in GH-10478
(commit 97d2c5da2f).

CHANGES

@@ -4,6 +4,8 @@ Release 7.2.4 (in development)
 Bugs fixed
 ----------
 
+* #11618: Fix a regression in the MoveModuleTargets transform,
+  introduced in #10478 (#9662).
 
 Release 7.2.3 (released Aug 23, 2023)
 =====================================

sphinx/transforms/__init__.py

@@ -145,10 +145,14 @@ class MoveModuleTargets(SphinxTransform):
         for node in list(self.document.findall(nodes.target)):
             if not node['ids']:
                 continue
-            if ('ismod' in node and
-                    node.parent.__class__ is nodes.section and
-                    # index 0 is the section title node
-                    node.parent.index(node) == 1):
+            if (
+                'ismod' in node
+                and type(node.parent) is nodes.section
+                # index 0: section title node
+                # index 1: index node
+                # index 2: target node
+                and node.parent.index(node) == 2
+            ):
                 node.parent['ids'][0:0] = node['ids']
                 node.parent.remove(node)
 

tests/test_transforms_move_module_targets.py

@@ -0,0 +1,77 @@
+import pytest
+from docutils import nodes
+
+from sphinx import addnodes
+from sphinx.testing.util import SphinxTestApp
+from sphinx.transforms import MoveModuleTargets
+
+CONTENT_PY = """\
+move-module-targets
+===================
+
+.. py:module:: fish_licence.halibut
+"""
+CONTENT_JS = """\
+move-module-targets
+===================
+
+.. js:module:: fish_licence.halibut
+"""
+
+
+@pytest.mark.parametrize('content', [
+    CONTENT_PY,  # Python
+    CONTENT_JS,  # JavaScript
+])
+@pytest.mark.usefixtures("rollback_sysmodules")
+def test_move_module_targets(tmp_path, content):
+    # Test for the MoveModuleTargets transform
+    tmp_path.joinpath("conf.py").touch()
+    tmp_path.joinpath("index.rst").write_text(content, encoding="utf-8")
+
+    app = SphinxTestApp('dummy', srcdir=tmp_path)
+    app.build(force_all=True)
+    document = app.env.get_doctree('index')
+    section = document[0]
+
+    # target ID has been lifted into the section node
+    assert section["ids"] == ['module-fish_licence.halibut', 'move-module-targets']
+    # nodes.target has been removed from 'section'
+    assert isinstance(section[0], nodes.title)
+    assert isinstance(section[1], addnodes.index)
+    assert len(section) == 2
+
+
+@pytest.mark.usefixtures("rollback_sysmodules")
+def test_move_module_targets_no_section(tmp_path):
+    # Test for the MoveModuleTargets transform
+    tmp_path.joinpath("conf.py").touch()
+    tmp_path.joinpath("index.rst").write_text(".. py:module:: fish_licence.halibut\n", encoding="utf-8")
+
+    app = SphinxTestApp('dummy', srcdir=tmp_path)
+    app.build(force_all=True)
+    document = app.env.get_doctree('index')
+
+    assert document["ids"] == []
+
+
+@pytest.mark.usefixtures("rollback_sysmodules")
+def test_move_module_targets_disabled(tmp_path):
+    # Test for the MoveModuleTargets transform
+    tmp_path.joinpath("conf.py").touch()
+    tmp_path.joinpath("index.rst").write_text(CONTENT_PY, encoding="utf-8")
+
+    app = SphinxTestApp('dummy', srcdir=tmp_path)
+    app.registry.transforms.remove(MoveModuleTargets)  # disable the transform
+    app.build(force_all=True)
+    document = app.env.get_doctree('index')
+    section = document[0]
+
+    # target ID is not lifted into the section node
+    assert section["ids"] == ['move-module-targets']
+    assert section[2]["ids"] == ['module-fish_licence.halibut']
+    # nodes.target remains in 'section'
+    assert isinstance(section[0], nodes.title)
+    assert isinstance(section[1], addnodes.index)
+    assert isinstance(section[2], nodes.target)
+    assert len(section) == 3