fix(analyzer): only index Python files for IMPORTS resolution

build_import_index received every analyzed file (all languages) via
self.files, indexing them by dotted module name regardless of extension.
A Python `import pkg.mod` could then resolve to a same-named non-Python
file (e.g. pkg/mod.java) and create spurious IMPORTS edges.

Restrict the index to .py files. Add a regression test asserting a
.java sibling at the same dotted path is never indexed.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: DvirDukhan

api/analyzers/python/analyzer.py

@@ -155,10 +155,16 @@ def build_import_index(self, files: dict[Path, File], root: Path) -> object:
         suffix map tolerates ``src/``/``lib/`` layouts where the import name
         (``matplotlib.axes``) differs from the path-from-root
         (``lib.matplotlib.axes``).
+
+        Only Python files are indexed; ``files`` carries every analyzed
+        source file, and a Python ``import pkg.mod`` must not resolve to a
+        same-named non-Python file such as ``pkg/mod.java``.
         """
         exact: dict[str, File] = {}
         suffix: dict[str, File] = {}
         for fpath, file in files.items():
+            if fpath.suffix != '.py':
+                continue
             if self.is_dependency(str(fpath)):
                 continue
             parts = self._module_parts(fpath, root)

tests/analyzers/test_tree_sitter_base.py

@@ -75,3 +75,26 @@ def test_tree_sitter_multilanguage_fixture_graph_counts():
         {"Class": 3, "Function": 4, "Method": 2}
     )
     assert Counter(edge[0] for edge in graph.edges) == Counter({"DEFINES": 9})
+
+
+def test_build_import_index_skips_non_python_files():
+    """A Python ``import pkg.mod`` must not resolve to ``pkg/mod.java``.
+
+    ``build_import_index`` receives every analyzed file (all languages), so it
+    must only index ``.py`` files; otherwise a same-named non-Python file with
+    the same dotted path would create spurious ``IMPORTS`` edges.
+    """
+    analyzer = PythonAnalyzer()
+    root = Path("/repo")
+    py_file = File(root / "pkg" / "mod.py", None)
+    java_file = File(root / "pkg" / "mod.java", None)
+    files = {py_file.path: py_file, java_file.path: java_file}
+
+    index = analyzer.build_import_index(files, root)
+
+    assert index["exact"]["pkg.mod"] is py_file
+    assert index["suffix"]["pkg.mod"] is py_file
+    assert index["suffix"]["mod"] is py_file
+    # The .java file must not have been indexed under any dotted name.
+    assert java_file not in index["exact"].values()
+    assert java_file not in index["suffix"].values()