Handle typing collisions and add validation to a files module for overlaping declarations (#582)

* Fix 'typing' import collisions.

* Fix formatting.

* Fix self-test issues.

* Validation for modules, different typing configurations

* add readme

* make warning

* fix format

---------

Co-authored-by: Scott Hendricks <scott.hendricks@confluent.io>

tests/test_module_validation.py

@@ -0,0 +1,111 @@
+from typing import (
+    List,
+    Optional,
+    Set,
+)
+
+import pytest
+
+from betterproto.plugin.module_validation import ModuleValidator
+
+
+@pytest.mark.parametrize(
+    ["text", "expected_collisions"],
+    [
+        pytest.param(
+            ["import os"],
+            None,
+            id="single import",
+        ),
+        pytest.param(
+            ["import os", "import sys"],
+            None,
+            id="multiple imports",
+        ),
+        pytest.param(
+            ["import os", "import os"],
+            {"os"},
+            id="duplicate imports",
+        ),
+        pytest.param(
+            ["from os import path", "import os"],
+            None,
+            id="duplicate imports with alias",
+        ),
+        pytest.param(
+            ["from os import path", "import os as os_alias"],
+            None,
+            id="duplicate imports with alias",
+        ),
+        pytest.param(
+            ["from os import path", "import os as path"],
+            {"path"},
+            id="duplicate imports with alias",
+        ),
+        pytest.param(
+            ["import os", "class os:"],
+            {"os"},
+            id="duplicate import with class",
+        ),
+        pytest.param(
+            ["import os", "class os:", "  pass", "import sys"],
+            {"os"},
+            id="duplicate import with class and another",
+        ),
+        pytest.param(
+            ["def test(): pass", "class test:"],
+            {"test"},
+            id="duplicate class and function",
+        ),
+        pytest.param(
+            ["def test(): pass", "def test(): pass"],
+            {"test"},
+            id="duplicate functions",
+        ),
+        pytest.param(
+            ["def test(): pass", "test = 100"],
+            {"test"},
+            id="function and variable",
+        ),
+        pytest.param(
+            ["def test():", "    test = 3"],
+            None,
+            id="function and variable in function",
+        ),
+        pytest.param(
+            [
+                "def test(): pass",
+                "'''",
+                "def test(): pass",
+                "'''",
+                "def test_2(): pass",
+            ],
+            None,
+            id="duplicate functions with multiline string",
+        ),
+        pytest.param(
+            ["def test(): pass", "# def test(): pass"],
+            None,
+            id="duplicate functions with comments",
+        ),
+        pytest.param(
+            ["from test import (", "    A", "   B", "   C", ")"],
+            None,
+            id="multiline import",
+        ),
+        pytest.param(
+            ["from test import (", "    A", "   B", "   C", ")", "from test import A"],
+            {"A"},
+            id="multiline import with duplicate",
+        ),
+    ],
+)
+def test_module_validator(text: List[str], expected_collisions: Optional[Set[str]]):
+    line_iterator = iter(text)
+    validator = ModuleValidator(line_iterator)
+    valid = validator.validate()
+    if expected_collisions is None:
+        assert valid
+    else:
+        assert set(validator.collisions.keys()) == expected_collisions
+        assert not valid