Use apparent_repo_name only for repository_ctx

Repurposed `apparent_repo_name` to only work with `repository_ctx`
objects after finding solutions to other repository name related
problems in bazelbuild/rules_scala#1621.

The one problem I couldn't solve (elegantly) without this function was
setting a default target name for a generated repo. Technically, such
repos could require an attribute to mirror `name`, but that seems like a
terrible user experience.

MODULE.bazel

@@ -37,3 +37,6 @@ use_repo(as_extension_test_ext, "bar", "foo")
 
 use_all_repos_test_ext = use_extension("//tests:modules_test.bzl", "use_all_repos_test_ext", dev_dependency = True)
 use_repo(use_all_repos_test_ext, "baz", "qux")
+
+apparent_repo_name_test_ext = use_extension("//tests:extensions/apparent_repo_name.bzl", "apparent_repo_name_test_ext", dev_dependency = True)
+use_repo(apparent_repo_name_test_ext, "apparent-repo-name-test")

WORKSPACE

@@ -81,3 +81,7 @@ load("//tests/directory:external_directory_tests.bzl", "external_directory_tests
 external_directory_tests(name = "external_directory_tests")
 
 register_unittest_toolchains()
+
+load("//tests:extensions/apparent_repo_name.bzl", "apparent_repo_name_test_macro")
+
+apparent_repo_name_test_macro()

docs/modules_doc.md

@@ -7,21 +7,41 @@ Skylib module containing utilities for Bazel modules and module extensions.
 ## modules.apparent_repo_name
 
 <pre>
-modules.apparent_repo_name(<a href="#modules.apparent_repo_name-label_or_name">label_or_name</a>)
+modules.apparent_repo_name(<a href="#modules.apparent_repo_name-repository_ctx">repository_ctx</a>)
 </pre>
 
-Return a repository's apparent repository name.
+Generates a repository's apparent name from a repository_ctx object.
+
+Useful when generating the default top level `BUILD` target for the
+repository.
+
+Example:
+```starlark
+_ALIAS_TARGET_TEMPLATE = """alias(
+ name = "{name}",
+ actual = "@{target_repo_name}",
+ visibility = ["//visibility:public"],
+)
+"""
+
+def _alias_repository_impl(repository_ctx):
+ repository_ctx.file("BUILD", _ALIAS_TARGET_TEMPLATE.format(
+ name = apparent_repo_name(rctx),
+ target = rctx.attr.target_repo_name,
+ ))
+```
+
 
 **PARAMETERS**
 
 
 | Name | Description | Default Value |
 | :------------- | :------------- | :------------- |
-| <a id="modules.apparent_repo_name-label_or_name"></a>label_or_name | a Label or repository name string | none |
+| <a id="modules.apparent_repo_name-repository_ctx"></a>repository_ctx | a repository_ctx object | none |
 
 **RETURNS**
 
-The apparent repository name
+An apparent repo name derived from repository_ctx.name
 
 
 <a id="modules.as_extension"></a>

lib/modules.bzl

@@ -114,38 +114,44 @@ def _use_all_repos(module_ctx, reproducible = False):
  **extension_metadata_kwargs
  )
 
-_repo_attr = (
- "repo_name" if hasattr(Label("//:all"), "repo_name") else "workspace_name"
-)
+def _apparent_repo_name(repository_ctx):
+ """Generates a repository's apparent name from a repository_ctx object.
+
+ Useful when generating the default top level `BUILD` target for the
+ repository.
 
-def _apparent_repo_name(label_or_name):
- """Return a repository's apparent repository name.
+ Example:
+ ```starlark
+ _ALIAS_TARGET_TEMPLATE = \"\"\"alias(
+ name = "{name}",
+ actual = "@{target_repo_name}",
+ visibility = ["//visibility:public"],
+ )
+ \"\"\"
+
+ def _alias_repository_impl(repository_ctx):
+ repository_ctx.file("BUILD", _ALIAS_TARGET_TEMPLATE.format(
+ name = apparent_repo_name(rctx),
+ target = rctx.attr.target_repo_name,
+ ))
+ ```
 
  Args:
- label_or_name: a Label or repository name string
+ repository_ctx: a repository_ctx object
 
  Returns:
- The apparent repository name
+ An apparent repo name derived from repository_ctx.name
  """
- repo_name = getattr(label_or_name, _repo_attr, label_or_name).lstrip("@")
- delimiter_indices = []
+ repo_name = repository_ctx.name
 
  # Bazed on this pattern from the Bazel source:
  # com.google.devtools.build.lib.cmdline.RepositoryName.VALID_REPO_NAME
- for i in range(len(repo_name)):
+ for i in range(len(repo_name) - 1, -1, -1):
  c = repo_name[i]
  if not (c.isalnum() or c in "_-."):
- delimiter_indices.append(i)
-
- if len(delimiter_indices) == 0:
- # Already an apparent repo name, apparently.
- return repo_name
-
- if len(delimiter_indices) == 1:
- # The name is for a top level module, possibly containing a version ID.
- return repo_name[:delimiter_indices[0]]
+ return repo_name[i + 1:]
 
- return repo_name[delimiter_indices[-1] + 1:]
+ return repo_name
 
 modules = struct(
  as_extension = _as_extension,

tests/extensions/apparent_repo_name.bzl

@@ -0,0 +1,22 @@
+"""Repo rule and module extension used to test modules.apparent_repo_name"""
+
+load("//lib:modules.bzl", "modules")
+
+def _apparent_repo_name_test_repo_impl(repository_ctx):
+ repo_name = modules.apparent_repo_name(repository_ctx)
+ test_file = "repo-name.bzl"
+ repository_ctx.file("WORKSPACE")
+ repository_ctx.file("BUILD", """exports_files(["%s"])""" % test_file)
+ repository_ctx.file(test_file, "REPO_NAME = \"%s\"" % repo_name)
+
+apparent_repo_name_test_repo = repository_rule(
+ _apparent_repo_name_test_repo_impl,
+)
+
+def apparent_repo_name_test_macro(*args):
+ apparent_repo_name_test_repo(name = "apparent-repo-name-test")
+
+apparent_repo_name_test_ext = module_extension(
+ lambda _: apparent_repo_name_test_macro(),
+ doc = "Only used for testing modules.apparent_repo_name()",
+)

tests/modules_test.bzl

@@ -14,6 +14,7 @@
 
 """Test usage of modules.bzl."""
 
+load("@apparent-repo-name-test//:repo-name.bzl", "REPO_NAME")
 load("//lib:modules.bzl", "modules")
 load("//lib:unittest.bzl", "asserts", "unittest")
 load("//rules:build_test.bzl", "build_test")
@@ -54,91 +55,14 @@ def _apparent_repo_name_test(ctx):
 
  asserts.equals(
  env,
- "",
- modules.apparent_repo_name(""),
- msg = "Handles the empty string as input",
- )
-
- asserts.equals(
- env,
- "foo",
- modules.apparent_repo_name("foo"),
- msg = (
- "Return the original name unchanged if it doesn't start with `@`.",
- ),
- )
-
- asserts.equals(
- env,
- "foo",
- modules.apparent_repo_name("@foo"),
- msg = "Return the original name without `@` if already apparent.",
- )
-
- foo_label = Label("@foo")
- foo_canonical_name = getattr(
- foo_label,
- "repo_name" if hasattr(foo_label, "repo_name") else "workspace_name",
- )
- asserts.equals(
- env,
- "foo",
- modules.apparent_repo_name(foo_canonical_name),
- msg = "Return the apparent name from a canonical name string.",
- )
-
- asserts.equals(
- env,
- "",
- modules.apparent_repo_name(Label("//:all")),
- msg = "Returns the empty string for a main repository Label.",
- )
-
- asserts.equals(
- env,
- "",
- modules.apparent_repo_name(Label("@bazel_skylib//:all")),
+ "apparent-repo-name-test",
+ REPO_NAME,
  msg = " ".join([
- "Returns the empty string for a Label containing the main",
- "repository's module name.",
+ "Returns the original name unchanged under WORKSPACE, and",
+ "the apparent repo name under Bzlmod.",
  ]),
  )
 
- asserts.equals(
- env,
- "foo",
- modules.apparent_repo_name(Label("@foo")),
- msg = "Return the apparent name from a Label.",
- )
-
- asserts.equals(
- env,
- "rules_pkg",
- modules.apparent_repo_name(Label("@rules_pkg")),
- msg = " ".join([
- "Top level module repos have the canonical name delimiter at the",
- "end. Therefore, this should not return the empty string, but the",
- "name without the leading `@` and trailing delimiter.",
- ]),
- )
-
- asserts.equals(
- env,
- "stardoc" if _is_bzlmod_enabled else "io_bazel_stardoc",
- modules.apparent_repo_name(Label("@io_bazel_stardoc")),
- msg = " ".join([
- "Label values will already map bazel_dep repo_names to",
- "actual repo names under Bzlmod (no-op under WORKSPACE).",
- ]),
- )
-
- asserts.equals(
- env,
- "foo",
- modules.apparent_repo_name("foo+1.2.3"),
- msg = "Ignores version numbers in canonical repo names",
- )
-
  return unittest.end(env)
 
 apparent_repo_name_test = unittest.make(_apparent_repo_name_test)