Changes to CLI (#2401)

Co-authored-by: Callum Fleming <howzitcal@zohomail.com>
Co-authored-by: Adam Hopkins <adam@amhopkins.com>

sanic/cli/app.py

@@ -113,6 +113,14 @@ Or, a path to a directory to run as a simple HTTP server:
                 delimiter = ":" if ":" in self.args.module else "."
                 module_name, app_name = self.args.module.rsplit(delimiter, 1)
 
+                if module_name == "" and os.path.isdir(self.args.module):
+                    raise ValueError(
+                        "App not found.\n"
+                        "   Please use --simple if you are passing a "
+                        "directory to sanic.\n"
+                        f"   eg. sanic {self.args.module} --simple"
+                    )
+
                 if app_name.endswith("()"):
                     self.args.factory = True
                     app_name = app_name[:-2]
@@ -125,9 +133,18 @@ Or, a path to a directory to run as a simple HTTP server:
                 app_type_name = type(app).__name__
 
                 if not isinstance(app, Sanic):
+                    if callable(app):
+                        solution = f"sanic {self.args.module} --factory"
+                        raise ValueError(
+                            "Module is not a Sanic app, it is a"
+                            f"{app_type_name}\n"
+                            "  If this callable returns a"
+                            f"Sanic instance try: \n{solution}"
+                        )
+
                     raise ValueError(
                         f"Module is not a Sanic app, it is a {app_type_name}\n"
-                        f"  Perhaps you meant {self.args.module}.app?"
+                        f"  Perhaps you meant {self.args.module}:app?"
                     )
         except ImportError as e:
             if module_name.startswith(e.name):

tests/fake/factory.py

@@ -0,0 +1,6 @@
+from sanic import Sanic
+
+
+def run():
+    app = Sanic("FactoryTest")
+    return app

tests/test_cli.py

@@ -57,6 +57,22 @@ def test_server_run(appname):
     assert firstline == b"Goin' Fast @ http://127.0.0.1:8000"
 
 
+def test_error_with_function_as_instance_without_factory_arg():
+    command = ["sanic", "fake.factory.run"]
+    out, err, exitcode = capture(command)
+    assert b"try: \nsanic fake.factory.run --factory" in err
+    assert exitcode != 1
+
+
+def test_error_with_path_as_instance_without_simple_arg():
+    command = ["sanic", "./fake/"]
+    out, err, exitcode = capture(command)
+    assert (
+        b"Please use --simple if you are passing a directory to sanic." in err
+    )
+    assert exitcode != 1
+
+
 @pytest.mark.parametrize(
     "cmd",
     (