wip

Author: aignas

examples/bzlmod/MODULE.bazel

@@ -37,6 +37,17 @@ python.toolchain(
     python_version = "3.10",
 )
 
+# One can override the actual toolchain versions that are available
+python.override(
+    available_python_versions = [
+        "3.10.9",
+        "3.9.19",
+    ],
+)
+python.version_override(
+    version = "3.10.2",
+)
+
 # You only need to load this repositories if you are using multiple Python versions.
 # See the tests folder for various examples on using multiple Python versions.
 # The names "python_3_9" and "python_3_10" are autmatically created by the repo

python/private/python.bzl

@@ -289,15 +289,20 @@ def _process_tag_classes(mod):
         for tag in mod.tags.override:
             base_url = tag.base_url
             if tag.available_python_versions:
+                all_known_versions = sorted(available_versions)
                 available_versions = {
-                    v: available_versions[v]
+                    v: available_versions.get(v, fail("unknown version {}, known versions: {}".format(
+                        v,
+                        all_known_versions,
+                    )))
                     for v in tag.available_python_versions
                 }
 
             if tag.register_all_versions and mod.name != "rules_python":
                 fail("This override can only be used by 'rules_python'")
             elif tag.register_all_versions:
                 register_all = True
+
             break
 
         if register_all: