feat: return bzlmod extension metadata for declared repositories (#237)

- Update `bazel_binaries` extension to return metadata listing the
declared repositories.
- Update `custom_test_runner` test to properly declare its repositories.

Closes #235.

MODULE.bazel

@@ -19,7 +19,13 @@ bazel_binaries = use_extension(
 )
 bazel_binaries.download(version_file = "//:.bazelversion")
 bazel_binaries.download(version = "6.4.0")
-use_repo(bazel_binaries, "bazel_binaries")
+use_repo(
+    bazel_binaries,
+    "bazel_binaries",
+    "bazel_binaries_bazelisk",
+    "build_bazel_bazel_.bazelversion",
+    "build_bazel_bazel_6_4_0",
+)
 
 download_sample_file = use_extension(
     "//examples/env_var_with_rootpath:sample_file_extension.bzl",

bazel_integration_test/bzlmod/bazel_binaries.bzl

@@ -131,19 +131,35 @@ version, version_file.\
 _BAZELISK_VERSION = "1.18.0"
 
 def _bazel_binaries_impl(module_ctx):
+    dep_names = []
+    dev_dep_names = []
+
+    def _add_dep_name(name, is_dev_dependency):
+        if is_dev_dependency:
+            dev_dep_names.append(name)
+        else:
+            dep_names.append(name)
+
+    ext_is_dev_dep = not module_ctx.root_module_has_non_dev_dependency
+
     # Create a repository for the bazelisk binary.
     bazelisk_repo_name = "bazel_binaries_bazelisk"
     _bazelisk_binary_repo_rule(
         name = bazelisk_repo_name,
         version = _BAZELISK_VERSION,
     )
+    _add_dep_name(bazelisk_repo_name, is_dev_dependency = ext_is_dev_dep)
 
     # Create version-specific bazel repos.
     version_infos = []
     for mod in module_ctx.modules:
         for download in mod.tags.download:
             vi = _declare_bazel_binary(download, bazelisk_repo_name)
             version_infos.append(vi)
+            _add_dep_name(
+                vi.repo_name,
+                is_dev_dependency = module_ctx.is_dev_dependency(download),
+            )
 
     if len(version_infos) == 0:
         fail("No versions were specified.")
@@ -158,11 +174,18 @@ def _bazel_binaries_impl(module_ctx):
         if current_vi == None:
             current_vi = version_infos[0]
 
+    bazel_binaries_repo_name = "bazel_binaries"
     _bazel_binaries_helper(
-        name = "bazel_binaries",
+        name = bazel_binaries_repo_name,
         version_to_repo = version_to_repo,
         current_version = current_vi.version,
     )
+    _add_dep_name(bazel_binaries_repo_name, is_dev_dependency = ext_is_dev_dep)
+
+    return module_ctx.extension_metadata(
+        root_module_direct_deps = dep_names,
+        root_module_direct_dev_deps = dev_dep_names,
+    )
 
 _download_tag = tag_class(
     attrs = {

examples/custom_test_runner/MODULE.bazel

@@ -34,7 +34,12 @@ bazel_binaries = use_extension(
     dev_dependency = True,
 )
 bazel_binaries.download(version_file = "//:.bazelversion")
-use_repo(bazel_binaries, "bazel_binaries")
+use_repo(
+    bazel_binaries,
+    "bazel_binaries",
+    "bazel_binaries_bazelisk",
+    "build_bazel_bazel_.bazelversion",
+)
 
 # swift_deps START
 swift_deps = use_extension(