commit ec04b5431181421608c8ce55d1cb53626d51ab3e
Author: Yun Peng <pcloudy@google.com>
Date:   Tue Jan 30 11:39:34 2024 +0100

    Add targets to make it easier to vendor the `@maven` repository

    This change is required to support Bazel's offline bootstrap build.
    More context in https://github.com/bazelbuild/bazel/pull/17112

    Instead of checking in jar files in Bazel's source tree, Bazel wants to use rules_jvm_external
    to fetch jars dependencies. However, to support Bazel's bootstrap build,
    we need to patch rules_jvm_external for vendoring the @maven repository.

    - Generate a BUILD.vendor file to be used in the vendored `@maven` repository.
      Added a jvm_import and a filegroup rule for each downloaded jar artifact.
      The filegroup rule is required by the bootstrap Java toolchain used in Bazel's
      bootstrap build. The bootstrap Java toolchain cannot depend on a jvm_import target.
      Because the jvm_import rule depends on a java_binary tool "AddJarManifestEntry",
      which requires a Java toolchain. Depending on the jar via a filegroup rule helps
      avoid this cyclic dependency.
    - Added a filegroup rule to collect all sources needed for vendoring `@maven`,
      including BUILD.vendor, WORKSPACE and jar files.

diff --git a/coursier.bzl b/coursier.bzl
index c60c590..7b16164 100644
--- a/coursier.bzl
+++ b/coursier.bzl
@@ -53,6 +53,12 @@ bzl_library(
 )
 """

+_BUILD_VENDOR = """
+load("@rules_jvm_external//private/rules:jvm_import.bzl", "jvm_import")
+
+{vendor_targets}
+"""
+
 DEFAULT_AAR_IMPORT_LABEL = "@build_bazel_rules_android//android:rules.bzl"

 _AAR_IMPORT_STATEMENT = """\
@@ -593,7 +599,7 @@ def _pinned_coursier_fetch_impl(repository_ctx):
     )

     repository_ctx.report_progress("Generating BUILD targets..")
-    (generated_imports, jar_versionless_target_labels) = parser.generate_imports(
+    (generated_imports, jar_versionless_target_labels, generated_vendor_targets) = parser.generate_imports(
         repository_ctx = repository_ctx,
         dependencies = importer.get_artifacts(maven_install_json_content),
         explicit_artifacts = {
@@ -633,6 +639,14 @@ def _pinned_coursier_fetch_impl(repository_ctx):
         executable = False,
     )

+    repository_ctx.file(
+        "BUILD.vendor",
+        (_BUILD_VENDOR).format(
+            vendor_targets = generated_vendor_targets,
+        ),
+        executable = False,
+    )
+
     _add_outdated_files(repository_ctx, artifacts, repositories)

     # Generate a compatibility layer of external repositories for all jar artifacts.
@@ -1153,7 +1167,7 @@ def _coursier_fetch_impl(repository_ctx):
     )

     repository_ctx.report_progress("Generating BUILD targets..")
-    (generated_imports, jar_versionless_target_labels) = parser.generate_imports(
+    (generated_imports, jar_versionless_target_labels, _) = parser.generate_imports(
         repository_ctx = repository_ctx,
         dependencies = v2_lock_file.get_artifacts(lock_file_contents),
         explicit_artifacts = {
diff --git a/private/dependency_tree_parser.bzl b/private/dependency_tree_parser.bzl
index 103fe5e..21159ed 100644
--- a/private/dependency_tree_parser.bzl
+++ b/private/dependency_tree_parser.bzl
@@ -76,7 +76,8 @@ def _generate_target(
         neverlink_artifacts,
         testonly_artifacts,
         default_visibilities,
-        artifact):
+        artifact,
+        vendor_targets):
     to_return = []
     simple_coord = strip_packaging_and_classifier_and_version(artifact["coordinates"])
     target_label = escape(simple_coord)
@@ -284,6 +285,7 @@ def _generate_target(
     target_import_string.append(")")

     to_return.append("\n".join(target_import_string))
+    vendor_targets.append("\n".join(target_import_string))

     # 10. Create a versionless alias target
     #
@@ -294,6 +296,9 @@ def _generate_target(
     versioned_target_alias_label = escape(strip_packaging_and_classifier(artifact["coordinates"]))
     to_return.append("alias(\n\tname = \"%s\",\n\tactual = \"%s\",\n%s)" %
                      (versioned_target_alias_label, target_label, alias_visibility))
+    file_group_target_string = "filegroup(\n\tname = \"%s\",\n\tsrcs = [\"%s\"],\n%s)" % (target_label + "_file", artifact_path, alias_visibility)
+    to_return.append(file_group_target_string)
+    vendor_targets.append(file_group_target_string)

     # 11. If using maven_install.json, use a genrule to copy the file from the http_file
     # repository into this repository.
@@ -356,6 +361,9 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
                     if repository_ctx.attr.maven_install_json:
                         all_imports.append(_genrule_copy_artifact_from_http_file(artifact, default_visibilities))

+    artifact_paths = []
+    vendor_targets = []
+
     # Iterate through the list of artifacts, and generate the target declaration strings.
     for artifact in dependencies:
         artifact_path = artifact["file"]
@@ -390,9 +398,9 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
             # Override target labels with the user provided mapping, instead of generating
             # a jvm_import/aar_import based on information in dep_tree.
             seen_imports[target_label] = True
-            all_imports.append(
-                "alias(\n\tname = \"%s\",\n\tactual = \"%s\",\n\tvisibility = [\"//visibility:public\"],)" % (target_label, labels_to_override.get(target_label)),
-            )
+            alias = "alias(\n\tname = \"%s\",\n\tactual = \"%s\",\n\tvisibility = [\"//visibility:public\"],)" % (target_label, labels_to_override.get(target_label))
+            all_imports.append(alias)
+            vendor_targets.append(alias)
             if repository_ctx.attr.maven_install_json:
                 # Provide the downloaded artifact as a file target.
                 all_imports.append(_genrule_copy_artifact_from_http_file(artifact, default_visibilities))
@@ -412,6 +420,7 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
                 testonly_artifacts,
                 default_visibilities,
                 raw_artifact,
+                vendor_targets,
             ))

         elif artifact_path != None:
@@ -426,7 +435,9 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
                 testonly_artifacts,
                 default_visibilities,
                 artifact,
+                vendor_targets,
             ))
+            artifact_paths.append("\"%s\"" % artifact_path)
         else:  # artifact_path == None:
             # Special case for certain artifacts that only come with a POM file.
             # Such artifacts "aggregate" their dependencies, so they don't have
@@ -479,7 +490,10 @@ def _generate_imports(repository_ctx, dependencies, explicit_artifacts, neverlin
             all_imports.append("alias(\n\tname = \"%s\",\n\tactual = \"%s\",\n%s)" %
                                (versioned_target_alias_label, target_label, alias_visibility))

-    return ("\n".join(all_imports), jar_versionless_target_labels)
+    all_imports.append("filegroup(\n\tname = \"srcs\",\n\tsrcs = [\n\t\t%s,\n\t],\n\tvisibility = [\"//visibility:public\"],\n)" %
+                       (",\n\t\t".join(["\"BUILD.vendor\"", "\"defs.bzl\"", "\"REPO.bazel\""] + artifact_paths)))
+
+    return ("\n".join(all_imports), jar_versionless_target_labels, "\n".join(vendor_targets))

 parser = struct(
     generate_imports = _generate_imports,