Create the @scala_compiler_sources repo (bazel-contrib#1635)

* Create the `@scala_compiler_sources` repo

Contains aliases to versioned Scala compiler source repository targets.
Part of bazel-contrib#1482.

Updates the version specific repo references in the srcs attribute of
`//third_party/dependency_analyzer/src/main/io/bazel/rulesscala/dependencyanalyzer/compiler:dep_reporting_compiler`.
Now these are references to versioned targets in
`@scala_compiler_sources//`, which are aliases to those versioned
compiler source repos.

In a Bzlmod world, this enables `rules_scala` to import only the
`scala_compiler_sources` repo in `MODULE.bazel`, instead of importing
each individual versioned compiler source repo.

This then allows `rules_scala` clients to set multiple `SCALA_VERSIONS`
without requiring them to import this repo or any versioned compiler
source repo. The Bzlmodifcation of the test repos under `dt_patches`
(coming in a future change) revealed the need for this flexibility.

* Push select() into @scala_compiler_sources//:src

Requested by @simuons in bazel-contrib#1635.

Author: mbland

scala/private/macros/scala_repositories.bzl

@@ -25,6 +25,37 @@ dt_patched_compiler = repository_rule(
     implementation = _dt_patched_compiler_impl,
 )
 
+_COMPILER_SOURCE_ALIAS_TEMPLATE = """alias(
+    name = "src",
+    visibility = ["//visibility:public"],
+    actual = select({{{compiler_sources}
+    }}),
+)
+"""
+
+_COMPILER_SOURCES_ENTRY_TEMPLATE = """
+        "@io_bazel_rules_scala_config//:scala_version{scala_version_suffix}":
+            "@scala_compiler_source{scala_version_suffix}//:src","""
+
+def _compiler_sources_repo_impl(rctx):
+    sources = [
+        _COMPILER_SOURCES_ENTRY_TEMPLATE.format(
+            scala_version_suffix = version_suffix(scala_version),
+        )
+        for scala_version in SCALA_VERSIONS
+    ]
+    build_content = _COMPILER_SOURCE_ALIAS_TEMPLATE.format(
+        compiler_sources = "".join(sources),
+    )
+    rctx.file("BUILD", content = build_content, executable = False)
+
+compiler_sources_repo = repository_rule(
+    implementation = _compiler_sources_repo_impl,
+    attrs = {
+        "scala_versions": attr.string_list(mandatory = True),
+    },
+)
+
 def _validate_scalac_srcjar(srcjar):
     if type(srcjar) != "dict":
         return False
@@ -137,6 +168,11 @@ def rules_scala_setup(scala_compiler_srcjar = None):
     for scala_version in SCALA_VERSIONS:
         dt_patched_compiler_setup(scala_version, scala_compiler_srcjar)
 
+    compiler_sources_repo(
+        name = "scala_compiler_sources",
+        scala_versions = SCALA_VERSIONS,
+    )
+
 def _artifact_ids(scala_version):
     return [
         "io_bazel_rules_scala_scala_library",

third_party/dependency_analyzer/src/main/io/bazel/rulesscala/dependencyanalyzer/compiler/BUILD

@@ -1,13 +1,8 @@
 load("//scala:scala.bzl", "scala_library_for_plugin_bootstrapping")
-load("@io_bazel_rules_scala_config//:config.bzl", "SCALA_VERSIONS")
-load("@io_bazel_rules_scala//scala:scala_cross_version.bzl", "version_suffix")
 
 scala_library_for_plugin_bootstrapping(
     name = "dep_reporting_compiler",
-    srcs = select({
-        "@io_bazel_rules_scala_config//:scala_version" + version_suffix(v): ["@scala_compiler_source%s//:src" % version_suffix(v)]
-        for v in SCALA_VERSIONS
-    }),
+    srcs = ["@scala_compiler_sources//:src"],
     scalac_jvm_flags = ["-Xmx128M"],  # fixme - workaround for a failing test
     visibility = ["//visibility:public"],
     deps = ["//scala/private/toolchain_deps:scala_compile_classpath"],