C, warn on tag mismatch

Author: jakobandersen

sphinx/domains/c.py

@@ -3784,6 +3784,22 @@ def _resolve_xref_inner(self, env: BuildEnvironment, fromdocname: str, builder:
                 return None, None
             # TODO: conditionally warn about xrefs with incorrect tagging?
 
+        # check if tags are used correctly
+        sName = s.get_full_nested_name()
+        assert len(name.names) <= len(sName.names)
+        for n, ns in zip(reversed(name.names), reversed(sName.names)):
+            if n.tag is None:
+                continue
+            assert ns.tag is not None
+            assert (n.tag == '') == (ns.tag == '')
+            if n.tag != ns.tag:
+                logger.warning(
+                    "C '%s' cross-reference uses wrong tag:"
+                    " reference name is '%s' but found name is '%s'."
+                    " Full reference name is '%s'."
+                    " Full found name is '%s'.",
+                    typ, n, ns, name, sName, location=node)
+
         # TODO: check role type vs. object type
 
         declaration = s.declaration

tests/roots/test-domain-c/wrong-tags.rst

@@ -0,0 +1,14 @@
+.. c:namespace:: @wrong_tag
+
+.. c:struct:: A
+
+	.. c:var:: int i
+
+- :c:var:`A.i`
+- :c:var:`union A.i`
+- :c:var:`enum A.i`
+
+.. c:function:: void f1(union A a)
+.. c:function:: void f2(enum A a)
+
+.. c:var:: int union A.j

tests/test_domain_c.py

@@ -688,6 +688,26 @@ def test_duplicate_tags(app, warning):
     assert "Declaration is '.. c:enum:: A'." in ws[3]
 
 
+@pytest.mark.sphinx(testroot='domain-c', confoverrides={'nitpicky': True})
+def test_build_domain_c_wrong_tags(app, warning):
+    app.builder.build_all()
+    ws = filter_warnings(warning, "wrong-tags")
+    template = ".rst:%d: WARNING: C '%s' cross-reference uses wrong tag:"\
+               " reference name is '%s' but found name is '%s'."\
+               " Full reference name is '%s'."\
+               " Full found name is '%s'."
+    expected = [
+        template % (8, 'var', 'union A', 'struct A', 'union A.i', '@wrong_tag.struct A.i'),
+        template % (9, 'var', 'enum A', 'struct A', 'enum A.i', '@wrong_tag.struct A.i'),
+        template % (11, 'identifier', 'union A', 'struct A', 'union A', '@wrong_tag.struct A'),
+        template % (13, 'identifier', 'enum A', 'struct A', 'enum A', '@wrong_tag.struct A'),
+        template % (14, 'identifier', 'union A', 'struct A', 'union A', '@wrong_tag.struct A'),
+    ]
+    for i in range(len(expected)):
+        assert expected[i] in ws[i]
+    assert len(ws) == len(expected)
+
+
 def test_build_domain_c_semicolon(app, warning):
     text = """
 .. c:member:: int member;