Add a regression test for the issue's own repro

A module aliased from a different file now resolves to that module's
real, non dangling node.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
(cherry picked from commit 53877c6874)

tests/test_elixir_import_resolution.py

@@ -0,0 +1,73 @@
+"""Elixir cross-file alias/import/require/use resolution (#2556).
+
+`extract_elixir` mints a module's own node id with the defining file's stem
+(`_make_id(stem, module_name)`) but an alias/import/require/use target with
+just the bare module name (`_make_id(module_name)`) -- the two can only
+match when a module refers to itself, so a reference to a module declared
+in ANY other file was silently dropped as dangling at build time. On a real
+900-file Elixir/Phoenix project this discarded 13% of extracted edges --
+the entire internal module dependency graph.
+"""
+from __future__ import annotations
+
+from pathlib import Path
+
+from graphify.extract import extract
+
+
+def _extract(tmp_path: Path, files: dict[str, str]):
+    paths = []
+    for name, body in files.items():
+        path = tmp_path / name
+        path.parent.mkdir(parents=True, exist_ok=True)
+        path.write_text(body, encoding="utf-8")
+        paths.append(path)
+    return extract(paths, cache_root=tmp_path / "graphify-out")
+
+
+def _find(result: dict, label: str, id_contains: str = "") -> str:
+    return next(
+        node["id"]
+        for node in result["nodes"]
+        if node.get("label") == label and id_contains in node["id"]
+    )
+
+
+def _find_file(result: dict, filename: str) -> str:
+    """An `imports` edge's source is the FILE node (extract_elixir emits it
+    at file scope), not the module node the file happens to declare."""
+    return next(
+        node["id"]
+        for node in result["nodes"]
+        if node.get("label") == filename
+    )
+
+
+_REPRO_CORPUS = {
+    "lib/demo/accounts.ex": (
+        "defmodule Demo.Accounts do\n"
+        "  def list_users, do: []\n"
+        "end\n"
+    ),
+    "lib/demo/web.ex": (
+        "defmodule Demo.Web do\n"
+        "  alias Demo.Accounts\n"
+        "\n"
+        "  def index, do: Accounts.list_users()\n"
+        "end\n"
+    ),
+}
+
+
+def test_alias_resolves_to_the_module_declared_in_another_file(tmp_path: Path):
+    result = _extract(tmp_path, _REPRO_CORPUS)
+    web_file = _find_file(result, "web.ex")
+    accounts = _find(result, "Demo.Accounts")
+    imports = {
+        (e["source"], e["target"])
+        for e in result["edges"]
+        if e["relation"] == "imports"
+    }
+    assert (web_file, accounts) in imports
+    node_ids = {n["id"] for n in result["nodes"]}
+    assert accounts in node_ids, "the import target must be a real, non-dangling node"