feat: support user-defined functions and classes in Ren'Py python

- Converter: def/return/global/nonlocal, class (inheritance, property,
  staticmethod, classmethod), lambda, *args/**kwargs and call-site unpacking.
  Unsupported dunder methods, generators and unknown decorators are still refused
- Player: closures, super(), instances that survive save/load, isinstance,
  hasattr/getattr/setattr, map/filter/sorted(key=), recursion limit
- audit_ir accepts calls to names, classes and methods the game defines itself;
  unknown renpy.* calls still block the import. Volume/pan/pause/replay calls
  are accepted as presentation-only no-ops; build.* settings are skipped
- Tests: IR fixture compiled from tests/fixtures/classes.py (tests/make_ir.py)
  and run in the interpreter; converter tests updated

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

backend/tests/make_ir.py

@@ -0,0 +1,17 @@
+"""Compile a Python file to PGVN IR JSON: python -m tests.make_ir SOURCE.py OUT.json"""
+import json
+import sys
+from pathlib import Path
+
+from app import pgvn
+from app.converter import pyexpr
+
+
+def main(source: Path, out: Path) -> None:
+    code = pyexpr.parse_stmts(source.read_text(encoding="utf-8"))
+    pgvn.statements(code)
+    out.write_text(json.dumps(code, ensure_ascii=False, separators=(",", ":")), encoding="utf-8")
+
+
+if __name__ == "__main__":
+    main(Path(sys.argv[1]), Path(sys.argv[2]))

backend/tests/test_compatibility.py

@@ -78,7 +78,7 @@ def test_renpy_only_declarations_are_not_execution_blockers(tmp_path):
 
 
 @pytest.mark.parametrize("source,reason", [
-    ('init python:\n    def helper():\n        pass\nlabel start:\n    "Hi"', "init python"),
+    ('init python:\n    def helper():\n        yield 1\nlabel start:\n    "Hi"', "init python"),
     ('label start:\n    $ result = renpy.show_screen("map")', "renpy.show_screen"),
     ('label start:\n    jump missing', "missing"),
 ])

backend/tests/test_converter.py

@@ -29,7 +29,7 @@ def test_expr_translation():
     e = pyexpr.parse_expr("a >= 1 and 'x' in inv or not flag")
     assert e["k"] == "bool" and e["op"] == "or"
     with pytest.raises(pyexpr.Unsupported):
-        pyexpr.parse_expr("lambda: 1")
+        pyexpr.parse_expr("(y := 1)")
 
 
 def test_say_variants():
@@ -57,10 +57,43 @@ def test_if_chain_and_menu():
 
 
 def test_unsupported_python_is_reported_not_fatal():
-    d = parse("init python:\n    def f():\n        pass\n    x = 1\nlabel start:\n    $ y = x\n")
+    d = parse("init python:\n    def f():\n        yield 1\n    x = 1\nlabel start:\n    $ y = x\n")
     assert d.warnings and d.init_code[0]["op"] == "set"
 
 
+def test_user_functions_and_classes_are_interpreted_not_rejected():
+    from app.converter.compatibility import audit_ir
+
+    d = parse(
+        "init python:\n"
+        "    class Mood(object):\n"
+        "        def __init__(self, v=0):\n"
+        "            self.v = v\n"
+        "        def up(self, n=1):\n"
+        "            self.v += n\n"
+        "            return self\n"
+        "    def bonus(m, *rest, **kw):\n"
+        "        return m.up(2).v\n"
+        "default mood = Mood()\n"
+        "label start:\n"
+        "    $ x = bonus(mood)\n"
+        "    $ mood.up()\n")
+    audit_ir(d)
+    assert not d.warnings and not d.blockers
+    assert [s["op"] for s in d.init_code] == ["class", "def"]
+
+
+def test_unknown_renpy_calls_and_unsupported_class_features_are_still_reported():
+    from app.converter.compatibility import audit_ir
+
+    d = parse("label start:\n    $ renpy.no_such_call()\n    $ missing_function()\n")
+    audit_ir(d)
+    messages = " ".join(d.warnings)
+    assert "renpy.no_such_call" in messages and "missing_function" in messages
+    d = parse("init python:\n    class A(object):\n        def __eq__(self, other):\n            return True\n")
+    assert any("__eq__" in w for w in d.warnings)
+
+
 def test_full_pipeline(data_dir, tmp_path):
     archive = build(tmp_path / "sample.zip")
     steps = []