python: unify code to generate ID from value

In the following

    @pytest.mark.parametrize(..., ids=[val])

the ID values are only allowed to be `str`, `float`, `int` or `bool`.

In the following

    @pytest.mark.parametrize(..., [val])

    @pytest.mark.parametrize(..., [pytest.param(..., id=val])

a different code path is used, which also allows `bytes`, `complex`,
`re.Pattern`, `Enum` and anything with a `__name__`.

In the interest of consistency, use the latter code path for all cases.

src/_pytest/fixtures.py

@@ -939,10 +939,7 @@ def __init__(
         params: Optional[Sequence[object]],
         unittest: bool = False,
         ids: Optional[
-            Union[
-                Tuple[Union[None, str, float, int, bool], ...],
-                Callable[[Any], Optional[object]],
-            ]
+            Union[Tuple[Optional[object], ...], Callable[[Any], Optional[object]]]
         ] = None,
     ) -> None:
         self._fixturemanager = fixturemanager
@@ -1093,18 +1090,8 @@ def pytest_fixture_setup(
 
 
 def _ensure_immutable_ids(
-    ids: Optional[
-        Union[
-            Iterable[Union[None, str, float, int, bool]],
-            Callable[[Any], Optional[object]],
-        ]
-    ],
-) -> Optional[
-    Union[
-        Tuple[Union[None, str, float, int, bool], ...],
-        Callable[[Any], Optional[object]],
-    ]
-]:
+    ids: Optional[Union[Sequence[Optional[object]], Callable[[Any], Optional[object]]]]
+) -> Optional[Union[Tuple[Optional[object], ...], Callable[[Any], Optional[object]]]]:
     if ids is None:
         return None
     if callable(ids):
@@ -1148,9 +1135,8 @@ class FixtureFunctionMarker:
     scope: "Union[_ScopeName, Callable[[str, Config], _ScopeName]]"
     params: Optional[Tuple[object, ...]] = attr.ib(converter=_params_converter)
     autouse: bool = False
-    ids: Union[
-        Tuple[Union[None, str, float, int, bool], ...],
-        Callable[[Any], Optional[object]],
+    ids: Optional[
+        Union[Tuple[Optional[object], ...], Callable[[Any], Optional[object]]]
     ] = attr.ib(
         default=None,
         converter=_ensure_immutable_ids,
@@ -1191,10 +1177,7 @@ def fixture(
     params: Optional[Iterable[object]] = ...,
     autouse: bool = ...,
     ids: Optional[
-        Union[
-            Iterable[Union[None, str, float, int, bool]],
-            Callable[[Any], Optional[object]],
-        ]
+        Union[Sequence[Optional[object]], Callable[[Any], Optional[object]]]
     ] = ...,
     name: Optional[str] = ...,
 ) -> FixtureFunction:
@@ -1209,10 +1192,7 @@ def fixture(
     params: Optional[Iterable[object]] = ...,
     autouse: bool = ...,
     ids: Optional[
-        Union[
-            Iterable[Union[None, str, float, int, bool]],
-            Callable[[Any], Optional[object]],
-        ]
+        Union[Sequence[Optional[object]], Callable[[Any], Optional[object]]]
     ] = ...,
     name: Optional[str] = None,
 ) -> FixtureFunctionMarker:
@@ -1226,10 +1206,7 @@ def fixture(
     params: Optional[Iterable[object]] = None,
     autouse: bool = False,
     ids: Optional[
-        Union[
-            Iterable[Union[None, str, float, int, bool]],
-            Callable[[Any], Optional[object]],
-        ]
+        Union[Sequence[Optional[object]], Callable[[Any], Optional[object]]]
     ] = None,
     name: Optional[str] = None,
 ) -> Union[FixtureFunctionMarker, FixtureFunction]:
@@ -1271,7 +1248,7 @@ def fixture(
         the fixture.
 
     :param ids:
-        List of string ids each corresponding to the params so that they are
+        Sequence of ids each corresponding to the params so that they are
         part of the test id. If no ids are provided they will be generated
         automatically from the params.
 

src/_pytest/python.py

@@ -940,14 +940,17 @@ class IdMaker:
     # ParameterSet.
     idfn: Optional[Callable[[Any], Optional[object]]]
     # Optionally, explicit IDs for ParameterSets by index.
-    ids: Optional[Sequence[Union[None, str]]]
+    ids: Optional[Sequence[Optional[object]]]
     # Optionally, the pytest config.
     # Used for controlling ASCII escaping, and for calling the
     # :hook:`pytest_make_parametrize_id` hook.
     config: Optional[Config]
     # Optionally, the ID of the node being parametrized.
     # Used only for clearer error messages.
     nodeid: Optional[str]
+    # Optionally, the ID of the function being parametrized.
+    # Used only for clearer error messages.
+    func_name: Optional[str]
 
     def make_unique_parameterset_ids(self) -> List[str]:
         """Make a unique identifier for each ParameterSet, that may be used to
@@ -982,9 +985,7 @@ def _resolve_ids(self) -> Iterable[str]:
                 yield parameterset.id
             elif self.ids and idx < len(self.ids) and self.ids[idx] is not None:
                 # ID provided in the IDs list - parametrize(..., ids=[...]).
-                id = self.ids[idx]
-                assert id is not None
-                yield _ascii_escaped_by_config(id, self.config)
+                yield self._idval_from_value_required(self.ids[idx], idx)
             else:
                 # ID not provided - generate it.
                 yield "-".join(
@@ -1053,6 +1054,25 @@ def _idval_from_value(self, val: object) -> Optional[str]:
             return name
         return None
 
+    def _idval_from_value_required(self, val: object, idx: int) -> str:
+        """Like _idval_from_value(), but fails if the type is not supported."""
+        id = self._idval_from_value(val)
+        if id is not None:
+            return id
+
+        # Fail.
+        if self.func_name is not None:
+            prefix = f"In {self.func_name}: "
+        elif self.nodeid is not None:
+            prefix = f"In {self.nodeid}: "
+        else:
+            prefix = ""
+        msg = (
+            f"{prefix}ids contains unsupported value {saferepr(val)} (type: {type(val)!r}) at index {idx}. "
+            "Supported types are: str, bytes, int, float, complex, bool, enum, regex or anything with a __name__."
+        )
+        fail(msg, pytrace=False)
+
     @staticmethod
     def _idval_from_argname(argname: str, idx: int) -> str:
         """Make an ID for a parameter in a ParameterSet from the argument name
@@ -1182,10 +1202,7 @@ def parametrize(
         argvalues: Iterable[Union[ParameterSet, Sequence[object], object]],
         indirect: Union[bool, Sequence[str]] = False,
         ids: Optional[
-            Union[
-                Iterable[Union[None, str, float, int, bool]],
-                Callable[[Any], Optional[object]],
-            ]
+            Union[Iterable[Optional[object]], Callable[[Any], Optional[object]]]
         ] = None,
         scope: "Optional[_ScopeName]" = None,
         *,
@@ -1316,10 +1333,7 @@ def _resolve_parameter_set_ids(
         self,
         argnames: Sequence[str],
         ids: Optional[
-            Union[
-                Iterable[Union[None, str, float, int, bool]],
-                Callable[[Any], Optional[object]],
-            ]
+            Union[Iterable[Optional[object]], Callable[[Any], Optional[object]]]
         ],
         parametersets: Sequence[ParameterSet],
         nodeid: str,
@@ -1349,16 +1363,22 @@ def _resolve_parameter_set_ids(
             idfn = None
             ids_ = self._validate_ids(ids, parametersets, self.function.__name__)
         id_maker = IdMaker(
-            argnames, parametersets, idfn, ids_, self.config, nodeid=nodeid
+            argnames,
+            parametersets,
+            idfn,
+            ids_,
+            self.config,
+            nodeid=nodeid,
+            func_name=self.function.__name__,
         )
         return id_maker.make_unique_parameterset_ids()
 
     def _validate_ids(
         self,
-        ids: Iterable[Union[None, str, float, int, bool]],
+        ids: Iterable[Optional[object]],
         parametersets: Sequence[ParameterSet],
         func_name: str,
-    ) -> List[Union[None, str]]:
+    ) -> List[Optional[object]]:
         try:
             num_ids = len(ids)  # type: ignore[arg-type]
         except TypeError:
@@ -1373,22 +1393,7 @@ def _validate_ids(
             msg = "In {}: {} parameter sets specified, with different number of ids: {}"
             fail(msg.format(func_name, len(parametersets), num_ids), pytrace=False)
 
-        new_ids = []
-        for idx, id_value in enumerate(itertools.islice(ids, num_ids)):
-            if id_value is None or isinstance(id_value, str):
-                new_ids.append(id_value)
-            elif isinstance(id_value, (float, int, bool)):
-                new_ids.append(str(id_value))
-            else:
-                msg = (  # type: ignore[unreachable]
-                    "In {}: ids must be list of string/float/int/bool, "
-                    "found: {} (type: {!r}) at index {}"
-                )
-                fail(
-                    msg.format(func_name, saferepr(id_value), type(id_value), idx),
-                    pytrace=False,
-                )
-        return new_ids
+        return list(itertools.islice(ids, num_ids))
 
     def _resolve_arg_value_types(
         self,