Fix fastloop app initialization error (#17)

* Refactor infer_application_path to improve module discovery

Co-authored-by: luke <luke@smartshare.io>

* bump

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Luke Lombardi <luke@beam.cloud>

Author: 3 people

fastloop/fastloop.py

@@ -150,12 +150,16 @@ def run(
         config.graceful_timeout = shutdown_timeout
         config.debug = debug
 
+        # For debug/reload mode, we need an application path for hypercorn to reload
+        application_path = None
         if config.debug:
             config.use_reloader = True
-            if not hasattr(config, "application_path"):
-                config.application_path = infer_application_path(self)
+            application_path = infer_application_path(self)
+            if application_path:
+                config.application_path = application_path
 
-        if not hasattr(config, "application_path"):
+        # Use direct serve if no valid application_path (works without reload)
+        if not application_path:
             asyncio.run(hypercorn.asyncio.serve(self, config))
             return
 

fastloop/utils.py

@@ -47,8 +47,8 @@ def infer_application_path(app_instance: Any, fallback_var: str = "app") -> str
     """
     Infer the application path for Hypercorn reload support.
 
-    Try (1) to locate the app in its defining module and use 'module:var',
-    else (2) derive module from sys.argv[0] and use 'module:fallback_var'.
+    Searches loaded modules to find where app_instance is stored as a variable,
+    then falls back to argv-based inference.
 
     Args:
         app_instance: The FastLoop/FastAPI application instance
@@ -57,31 +57,47 @@ def infer_application_path(app_instance: Any, fallback_var: str = "app") -> str
     Returns:
         Application path string like "module.path:app" or None if cannot be determined
     """
-    # (1) Introspect app if it has an 'app' attribute (e.g., FastLoop wrapping FastAPI)
-    # Note: We don't fall back to app_instance here because app_instance.__module__
-    # would be "fastloop.fastloop" (where the class is defined), not the user's module.
-    # If there's no 'app' attribute, we fall through to argv-based inference.
-    app = getattr(app_instance, "app", None)
-    if app is not None and getattr(app, "__module__", None):
-        mod_name = app.__module__
+    # (1) Search loaded modules for the app_instance
+    # Skip fastloop package modules to avoid returning "fastloop.fastloop:app"
+    # which doesn't exist (FastLoop is a class, not an instance there)
+    for mod_name, mod in list(sys.modules.items()):
+        # Skip fastloop package, private modules, and None modules
+        if (
+            mod is None
+            or mod_name.startswith("fastloop")
+            or mod_name.startswith("_")
+        ):
+            continue
+
         try:
-            mod = importlib.import_module(mod_name)
             for name, val in vars(mod).items():
-                if val is app:
+                if val is app_instance:
                     return f"{mod_name}:{name}"
-            # app object found but variable name not recoverable — use fallback var
-            return f"{mod_name}:{fallback_var}"
-        except BaseException:
-            pass  # fall through to argv-based inference
+        except Exception:
+            continue
 
-    # (2) Derive dotted module from the script path in sys.argv[0]
+    # (2) If app_instance has an 'app' attribute, try that (for wrapper patterns)
+    app = getattr(app_instance, "app", None)
+    if app is not None and getattr(app, "__module__", None):
+        mod_name = app.__module__
+        # Skip fastloop package
+        if not mod_name.startswith("fastloop"):
+            try:
+                mod = importlib.import_module(mod_name)
+                for name, val in vars(mod).items():
+                    if val is app:
+                        return f"{mod_name}:{name}"
+            except Exception:
+                pass
+
+    # (3) Derive dotted module from the script path in sys.argv[0]
     script = Path(sys.argv[0]).resolve()
     if script.suffix == ".py":
         # Find the first sys.path entry that contains the script
         for base in map(Path, sys.path):
             try:
                 rel = script.relative_to(base.resolve())
-            except BaseException:
+            except Exception:
                 continue
 
             # Convert path/to/module.py -> path.to.module

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "fastloop"
-version = "0.1.73"
+version = "0.1.74"
 description = "A Python package for deploying stateful loops"
 readme = "README.md"
 requires-python = ">=3.12"

tests/test_app_initialization.py

@@ -75,6 +75,60 @@ def test_falls_back_to_argv_inference(self):
                     assert "myapp.main" in result
                     assert ":app" in result
 
+    def test_finds_app_in_external_module(self):
+        """
+        Regression test for app defined in separate module (like internal_agents.app).
+
+        When a FastLoop instance is created in a user module and imported into main,
+        infer_application_path should find it in that module.
+
+        This is the pattern:
+            # mypackage/app.py
+            app = FastLoop(name="my-app")
+
+            # mypackage/main.py
+            from mypackage.app import app
+            app.run()
+        """
+        import types
+
+        # Create a mock module simulating 'mypackage.app'
+        mock_module = types.ModuleType("mypackage.app")
+        app = FastLoop(name="external-module-app")
+        mock_module.app = app
+
+        # Register the mock module
+        sys.modules["mypackage.app"] = mock_module
+
+        try:
+            result = infer_application_path(app)
+
+            # Should find the app in our mock module
+            assert result is not None, "infer_application_path should find app in external module"
+            assert result == "mypackage.app:app", f"Expected 'mypackage.app:app', got '{result}'"
+            assert not result.startswith("fastloop."), "Should not resolve to fastloop package"
+        finally:
+            # Clean up
+            del sys.modules["mypackage.app"]
+
+    def test_finds_app_with_different_variable_name(self):
+        """Test that app is found even if stored with a different variable name."""
+        import types
+
+        mock_module = types.ModuleType("mypackage.server")
+        app = FastLoop(name="custom-var-app")
+        mock_module.my_server = app  # Different variable name
+
+        sys.modules["mypackage.server"] = mock_module
+
+        try:
+            result = infer_application_path(app)
+
+            assert result is not None
+            assert result == "mypackage.server:my_server"
+        finally:
+            del sys.modules["mypackage.server"]
+
 
 class TestFastLoopWithLoops:
     """Tests for FastLoop app with registered loops."""