feat: add --require-unique-paramset-ids option skips pytest internal logic of id generation

Author: gomri15

changelog/13737.feature.rst

@@ -0,0 +1,3 @@
+Added flag --require-unique-paramset-ids to pytest that when set to true will
+make pytest raise an exception when non-unique
+paramset ids are detected instead of attempting to generate them

src/_pytest/main.py

@@ -90,6 +90,13 @@ def pytest_addoption(parser: Parser) -> None:
         action="store_true",
         help="(Deprecated) alias to --strict-markers",
     )
+    group.addoption(
+        "--require-unique-paramset-ids",
+        action="store_true",
+        default=False,
+        help="Stops pytest automatically generating unique parameter set IDs. "
+        "and raises an error if there are any duplicates.",
+    )
 
     group = parser.getgroup("pytest-warnings")
     group.addoption(

src/_pytest/python.py

@@ -902,6 +902,25 @@ def make_unique_parameterset_ids(self) -> list[str | _HiddenParam]:
         resolved_ids = list(self._resolve_ids())
         # All IDs must be unique!
         if len(resolved_ids) != len(set(resolved_ids)):
+            if self.config and self.config.cache._config.getoption(
+                "require_unique_paramset_ids"
+            ):
+                duplicate_indexs = defaultdict(list)
+                for i, val in enumerate(resolved_ids):
+                    duplicate_indexs[val].append(i)
+
+                # Keep only duplicates
+                duplicates = {k: v for k, v in duplicate_indexs.items() if len(v) > 1}
+                raise Exception(f"""
+                    Because: require_unique_parameterset_ids is set, pytest won't
+                    attempt to generate unique IDs for parameter sets.
+                    argument values: {self.parametersets}
+                    argument names: {self.argnames}
+                    function name: {self.func_name}
+                    test name: {self.nodeid}
+                    resolved (with non-unique) IDs: {resolved_ids}
+                    duplicates: {duplicates}
+                    """)
             # Record the number of occurrences of each ID.
             id_counts = Counter(resolved_ids)
             # Map the ID to its next suffix.

testing/test_collection.py

@@ -2031,3 +2031,34 @@ def test_namespace_packages(pytester: Pytester, import_mode: str):
             "      <Function test_module3>",
         ]
     )
+
+
+@pytest.mark.parametrize(
+    "parametrize_args, expected_indexs",
+    [
+        ("[1, 1, 3]", "{'1': [[]0, 1[]]}"),
+        ("[1, 1, 3, 2, 2]", "{'1': [[]0, 1[]], '2': [[]3, 4[]]}"),
+    ],
+)
+def test_option_parametrize_require_unique_paramset_ids(
+    pytester: Pytester, parametrize_args, expected_indexs
+) -> None:
+    pytester.makepyfile(
+        f"""
+        import pytest
+        @pytest.mark.parametrize('y', {parametrize_args})
+        def test1(y):
+            pass
+    """
+    )
+    result = pytester.runpytest("--require-unique-paramset-ids")
+    result.stdout.fnmatch_lines(
+        [
+            "E*Because: require_unique_parameterset_ids is set, pytest won't",
+            "E*attempt to generate unique IDs for parameter sets.",
+            "E*argument names: [[]'y'[]]",
+            "E*function name: test1",
+            "E*test name: test_option_parametrize_require_unique_paramset_ids.py::test1",
+            f"E*duplicates: {expected_indexs!s}",
+        ]
+    )