Providers PEP: address review comments

peps/pep-9999.rst

@@ -16,7 +16,7 @@ Status: Draft
 Type: Standards Track
 Topic: Packaging
 Requires: 825
-Created: 21-Sep-2026
+Created: 22-Sep-2026
 Post-History: Pending
 
 Abstract
@@ -151,6 +151,10 @@ namespace:
    and feature values. For providers that were not trusted, it MUST
    assume that the list of compatible features is empty.
 
+For every unique provider, the tool MUST obtain the list of compatible
+features and their values only once throughout the install session and
+use it across all the packages being installed.
+
 
 Variant metadata
 ----------------
@@ -340,6 +344,10 @@ These can be implemented either as module-level functions, class methods
 or static methods. The specifics are provided in the subsequent
 sections.
 
+Any errors occurring while installing or executing the plugin API,
+including the plugin code terminating the calling process, MUST result
+in tools aborting the install process.
+
 
 API endpoint
 ''''''''''''
@@ -521,24 +529,31 @@ Example implementation
             # no runtime found, system not supported at all
             return []
 
-        return [
+        configs = [
             VariantFeatureConfig(
                 name="min_version",
                 # [current, current - 1, ..., 1]
                 values=[str(x) for x in range(current_version, 0, -1)],
                 multi_value=False,
             ),
-            VariantFeatureConfig(
-                name="gpu",
-                # this may be empty if no GPUs are supported --
-                # 'example :: gpu feature' is not supported then;
-                # but wheels with no GPU-specific code and only
-                # 'example :: min_version' could still be installed
-                values=[x for x in _ALL_GPUS if _is_gpu_available(x)],
-                multi_value=True,
-            ),
         ]
 
+        # this may be empty if no GPUs are supported --
+        # 'example :: gpu feature' is not supported then;
+        # but wheels with no GPU-specific code and only
+        # 'example :: min_version' could still be installed
+        supported_gpus = [x for x in _ALL_GPUS if _is_gpu_available(x)]
+        if supported_gpus:
+            configs.append(
+                VariantFeatureConfig(
+                    name="gpu",
+                    values=supported_gpus,
+                    multi_value=True,
+                )
+            )
+
+        return configs
+
 
 Future extensions
 '''''''''''''''''
@@ -573,16 +588,20 @@ with the same system.
 
 Within this namespace, zero or more properties can be used to express
 compatible dependency versions. For each property, the feature name MUST
-be the :ref:`normalized name <packaging:name-normalization>` of the
-dependency, whereas the value MUST be a valid release segment of a
-public version identifier, as defined by the
-:doc:`packaging:specifications/version-specifiers` specification. It
-MUST contain up to three version components, that are matched against
-the installed version same as the ``=={value}.*`` specifier. Notably,
-trailing zeroes match versions with fewer components (e.g. ``2.0``
-matches release ``2`` but not ``2.1``). This also implies that the
-property values have different semantics than PEP 440 versions, in
-particular ``2``, ``2.0`` and ``2.0.0`` represent different ranges.
+be the name of the dependency and the value MUST be a valid release
+segment of a public version identifier, as defined by the
+:doc:`packaging:specifications/version-specifiers` specification. Both
+the dependency name and version MUST be normalized according to the same
+rules as wheel files, as found in the
+:ref:`packaging:wheel-file-name-spec` of the Binary Distribution Format
+specification.
+
+The feature version MUST contain up to three version components, that
+are matched against the installed version same as the ``=={value}.*``
+specifier. Notably, trailing zeroes match versions with fewer components
+(e.g. ``2.0`` matches release ``2`` but not ``2.1``). This also implies
+that the property values have different semantics than PEP 440 versions,
+in particular ``2``, ``2.0`` and ``2.0.0`` represent different ranges.
 
 Versions with nonzero epoch are not supported.
 
@@ -765,24 +784,6 @@ The `variantlib <https://github.com/wheelnext/variantlib>`__ project
 contains a reference implementation of this PEP.
 
 
-Rejected Ideas
-==============
-
-An approach without provider plugins
-------------------------------------
-
-Rather than introducing provider plugins, the rules governing every
-variant namespace could be defined via PEPs. However, such an approach
-would be less scalable and impose additional effort on stakeholders, PEP
-editors and tool maintainers.
-
-Every new namespace would have to go through standardization process,
-followed by explicit implementation process. Deployment of new variant
-properties would be entirely dependent on tool updates. The added
-maintenance cost could lead to support for less popular variant axes not
-being accepted, or lack of feature parity between different tools.
-
-
 Acknowledgements
 ================
 
@@ -801,7 +802,7 @@ and Zanie Blue.
 Change History
 ==============
 
-- 21-Sep-2026
+- 22-Sep-2026
 
   - Initial version, split from :pep:`817` draft.
   - Namespaces have been removed from the `provider plugin API`_.
@@ -819,6 +820,12 @@ Change History
     required to be non-empty.
   - The entry point name is now used to provide the recommended
     namespace for a provider.
+  - The feature names and values in the `ABI Dependency Variant Provider
+    (Optional)`_ are now normalized according to the wheel normalization
+    rules, to match the restrictions in :pep:`825`.
+  - A provision has been added that a consistent list of compatible
+    feature names and values from a single provider must be used
+    throughout the install session.
 
 
 Appendices

peps/pep-9999/variant-schema-0.2.0.json

@@ -79,20 +79,30 @@
                   },
                   "minItems": 0,
                   "uniqueItems": true
-                },
-                "additionalProperties": false
-              }
+                }
+              },
+              "additionalProperties": false
             }
           },
           "additionalProperties": false,
           "oneOf": [
             {
               "required": ["requires"],
-              "not": {"required": ["feature-order"]}
+              "not": {
+                "anyOf": [
+                  { "required": ["feature-order"] },
+                  { "required": ["static-properties"] }
+                ]
+              }
             },
             {
               "required": ["static-properties"],
-              "not": {"required": ["plugin-api"]}
+              "not": {
+                "anyOf": [
+                  { "required": ["requires"] },
+                  { "required": ["plugin-api"] }
+                ]
+              }
             }
           ]
         }