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

Author: gomri15

changelog/13737.feature.rst

@@ -0,0 +1,4 @@
+Added the ``--require-unique-paramset-ids`` flag to pytest.
+
+When passed, this flag causes pytest to raise an exception upon detection of non-unique parameter set IDs,
+rather than attempting to generate them automatically.

doc/en/reference/reference.rst

@@ -2220,6 +2220,10 @@ All the command-line flags can be obtained by running ``pytest --help``::
       --doctest-continue-on-failure
                             For a given doctest, continue to run after the first
                             failure
+      --require-unique-paramset-ids
+                            If pytest generates non-unique parameter ids, raise an
+                            error rather than fixing this.  Useful if you collect in one
+                            process, and then execute tests in independent workers.
 
     test session debugging and configuration:
       -c, --config-file FILE

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="When passed, this flag causes pytest to raise an exception upon detection of non-unique parameter set IDs"
+        "rather than attempting to generate them automatically.",
+    )
 
     group = parser.getgroup("pytest-warnings")
     group.addoption(

src/_pytest/python.py

@@ -50,6 +50,7 @@
 from _pytest.config import Config
 from _pytest.config import hookimpl
 from _pytest.config.argparsing import Parser
+from _pytest.config.exceptions import UsageError
 from _pytest.deprecated import check_ispytest
 from _pytest.fixtures import FixtureDef
 from _pytest.fixtures import FixtureRequest
@@ -902,6 +903,25 @@ 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 UsageError(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

@@ -5,6 +5,7 @@
 from pathlib import Path
 from pathlib import PurePath
 import pprint
+import re
 import shutil
 import sys
 import tempfile
@@ -2031,3 +2032,40 @@ def test_namespace_packages(pytester: Pytester, import_mode: str):
             "      <Function test_module3>",
         ]
     )
+
+
+@pytest.mark.parametrize(
+    "parametrize_args, expected_indexs",
+    [
+        ("[(1, 1), (1, 1)]", {"1-1": [0, 1]}),
+        ("[(1, 1), (1, 2), (1, 1)]", {"1-1": [0, 2]}),
+        ("[(1, 1), (2, 2), (1, 1)]", {"1-1": [0, 2]}),
+        ("[(1, 1), (2, 2), (1, 2), (2, 1), (1, 1)]", {"1-1": [0, 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, x', {parametrize_args})
+        def test1(y, x):
+            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', 'x'[]]",
+            "E*function name: test1",
+            "E*test name: test_option_parametrize_require_unique_paramset_ids.py::test1",
+            f"E*duplicates: {fnmatch_escape_repr(expected_indexs)}",
+        ]
+    )
+
+
+def fnmatch_escape_repr(obj):
+    return re.sub(r"[*?[\]]", (lambda m: f"[{m.group()}]"), repr(obj))