Handle brackets in collection file paths

AUTHORS

@@ -211,6 +211,7 @@ Harald Armin Massa
 Harshna
 Henk-Jaap Wagenaar
 Henry Schreiner
+Himanshu
 Holger Kohr
 Hugo van Kemenade
 Hui Wang (coldnight)

changelog/15217.bugfix.rst

@@ -0,0 +1 @@
+Fixed test collection for Python files whose names contain square brackets.

src/_pytest/main.py

@@ -1152,11 +1152,19 @@ def resolve_collection_argument(
     If the path doesn't exist, raise UsageError.
     If the path is a directory and selection parts are present, raise UsageError.
     """
-    base, squacket, rest = arg.partition("[")
-    strpath, *parts = base.split("::")
-    if squacket and not parts:
+    selection_start = arg.find("::")
+    strpath = arg if selection_start == -1 else arg[:selection_start]
+    if "[" in strpath and not safe_exists(absolutepath(invocation_path / strpath)):
         raise UsageError(f"path cannot contain [] parametrization: {arg}")
-    parametrization = f"{squacket}{rest}" if squacket else None
+
+    path_and_parts = arg
+    parametrization = None
+    if selection_start != -1:
+        parametrization_start = arg.find("[", selection_start + 2)
+        if parametrization_start != -1:
+            path_and_parts = arg[:parametrization_start]
+            parametrization = arg[parametrization_start:]
+    strpath, *parts = path_and_parts.split("::")
     module_name = None
     if as_pypath:
         pyarg_strpath = search_pypath(

testing/test_main.py

@@ -166,6 +166,23 @@ def test_file(self, invocation_path: Path) -> None:
             original_index=40,
         )
 
+    def test_file_with_brackets_in_name(
+        self, invocation_path: Path, pytester: Pytester
+    ) -> None:
+        path = invocation_path / "src/pkg/test_[helper].py"
+        path.write_text("def test_example(): pass\n", encoding="utf-8")
+
+        assert resolve_collection_argument(invocation_path, str(path), 0) == (
+            CollectionArgument(
+                path=path,
+                parts=[],
+                parametrization=None,
+                module_name=None,
+                original_index=0,
+            )
+        )
+        pytester.runpytest(str(path)).assert_outcomes(passed=1)
+
     def test_dir(self, invocation_path: Path) -> None:
         """Directory and parts."""
         assert resolve_collection_argument(