Fix dmypy inspect on Windows (#16355)

Fixes #15780

mypy/inspections.py

@@ -215,13 +215,6 @@ def __init__(
         # Module for which inspection was requested.
         self.module: State | None = None
 
-    def parse_location(self, location: str) -> tuple[str, list[int]]:
-        if location.count(":") not in [2, 4]:
-            raise ValueError("Format should be file:line:column[:end_line:end_column]")
-        parts = location.split(":")
-        module, *rest = parts
-        return module, [int(p) for p in rest]
-
     def reload_module(self, state: State) -> None:
         """Reload given module while temporary exporting types."""
         old = self.fg_manager.manager.options.export_types
@@ -575,7 +568,7 @@ def run_inspection(
         This can be re-used by various simple inspections.
         """
         try:
-            file, pos = self.parse_location(location)
+            file, pos = parse_location(location)
         except ValueError as err:
             return {"error": str(err)}
 
@@ -617,3 +610,18 @@ def get_definition(self, location: str) -> dict[str, object]:
             result["out"] = f"No name or member expressions at {location}"
             result["status"] = 1
         return result
+
+
+def parse_location(location: str) -> tuple[str, list[int]]:
+    if location.count(":") < 2:
+        raise ValueError("Format should be file:line:column[:end_line:end_column]")
+    parts = location.rsplit(":", maxsplit=2)
+    start, *rest = parts
+    # Note: we must allow drive prefix like `C:` on Windows.
+    if start.count(":") < 2:
+        return start, [int(p) for p in rest]
+    parts = start.rsplit(":", maxsplit=2)
+    start, *start_rest = parts
+    if start.count(":") < 2:
+        return start, [int(p) for p in start_rest + rest]
+    raise ValueError("Format should be file:line:column[:end_line:end_column]")

mypy/test/testutil.py

@@ -3,6 +3,7 @@
 import os
 from unittest import TestCase, mock
 
+from mypy.inspections import parse_location
 from mypy.util import get_terminal_width
 
 
@@ -15,3 +16,7 @@ def test_get_terminal_size_in_pty_defaults_to_80(self) -> None:
         with mock.patch.object(os, "get_terminal_size", return_value=ret):
             with mock.patch.dict(os.environ, values=mock_environ, clear=True):
                 assert get_terminal_width() == 80
+
+    def test_parse_location_windows(self) -> None:
+        assert parse_location(r"C:\test.py:1:1") == (r"C:\test.py", [1, 1])
+        assert parse_location(r"C:\test.py:1:1:1:1") == (r"C:\test.py", [1, 1, 1, 1])

test-data/unit/daemon.test

@@ -372,6 +372,9 @@ foo.py:3: error: Incompatible types in assignment (expression has type "str", va
 $ dmypy inspect foo:1
 Format should be file:line:column[:end_line:end_column]
 == Return code: 2
+$ dmypy inspect foo:1:2:3
+Source file is not a Python file
+== Return code: 2
 $ dmypy inspect foo.py:1:2:a:b
 invalid literal for int() with base 10: 'a'
 == Return code: 2