Add a variant.json example

Signed-off-by: Michał Górny <mgorny@quansight.com>

Author: mgorny

peps/pep-0826.rst

@@ -190,6 +190,64 @@ keys:
   ``-`` characters with ``_`` in the normalized package name.
 
 
+Example
+'''''''
+
+.. code:: json5
+
+    {
+      // The schema URL will be replaced with the final URL on packaging.python.org
+      "$schema": "https://variants-schema.wheelnext.dev/v0.0.3.json",
+
+      "default-priorities": {
+        // MUST list all namespaces used.
+        "namespace": ["x86_64", "aarch64", "blas_lapack"],
+
+        // other fields same as in PEP 825
+        "feature": {},
+        "property": {}
+      },
+
+      "providers": {
+        // MUST list all namespaces used.
+        "aarch64": {
+          // Specifies provider plugin package. REQUIRED since there is no
+          // "static-properties" -- plugin will be queried at install time.
+          "requires": ["provider-variant-aarch64 >=0.0.1"],
+          // Overrides plugin API endpoint. OPTIONAL; without it, the API
+          // endpoint "provider_variant_aarch64" would be used.
+          "plugin-api": "provider_variant_aarch64.plugin:AArch64Plugin"
+        },
+        "blas_lapack": {
+          // Specifies compatible properties. No install-time querying is
+          // necessary.
+          "static-properties": {
+            // Values are ordered -- by default, openblas variant is preferred
+            over mkl, // and accelerate over the other two.
+            "library": ["accelerate", "openblas", "mkl"]
+          },
+          // OPTIONAL: unused since "static-properties" are available.
+          "requires": ["blas-lapack-variant-provider"]
+        },
+        "x86_64": {
+          // Specifies provider plugin package. REQUIRED since there is no
+          // "static-properties" -- plugin will be queried at install time.
+          "requires": [
+            "provider-variant-x86-64 >=0.0.1; python_version >= '3.12'",
+            "legacy-provider-variant-x86-64 >=0.0.1; python_version < '3.12'"
+          ],
+          // Overrides plugin API endpoint. REQUIRED since "requires" may
+          // evaluate to two different packages depending on Python version.
+          "plugin-api": "provider_variant_x86_64.plugin:X8664Plugin"
+        }
+      },
+
+      "variants": {
+        // same as in PEP 825
+      }
+    }
+
+
 Provider plugin API
 -------------------