commit 569fe4da2530d7b1356265d7cc62ca74f93ec7e5
Author: Yun Peng <pcloudy@google.com>
Date:   Thu Jan 5 16:37:29 2023 +0800

    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 901a6b0..d763f01 100644
--- a/coursier.bzl
+++ b/coursier.bzl
@@ -47,6 +47,12 @@ 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 = """\
@@ -577,7 +583,7 @@ 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,
         dep_tree = dep_tree,
         explicit_artifacts = {
@@ -616,6 +622,14 @@ 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.
@@ -1135,7 +1149,7 @@ 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,
         dep_tree = dep_tree,
         explicit_artifacts = {
diff --git a/private/dependency_tree_parser.bzl b/private/dependency_tree_parser.bzl
index 8515bf5..7653dea 100644
--- a/private/dependency_tree_parser.bzl
+++ b/private/dependency_tree_parser.bzl
@@ -107,6 +107,9 @@ def _generate_imports(repository_ctx, dep_tree, explicit_artifacts, neverlink_ar
     for jetify_include_artifact in repository_ctx.attr.jetify_include_list:
         jetify_include_dict[jetify_include_artifact] = None
 
+    artifact_paths = []
+    vendor_targets = []
+
     # Iterate through the list of artifacts, and generate the target declaration strings.
     for artifact in dep_tree["dependencies"]:
         artifact_path = artifact["file"]
@@ -336,6 +339,7 @@ def _generate_imports(repository_ctx, dep_tree, explicit_artifacts, neverlink_ar
             target_import_string.append(")")
 
             all_imports.append("\n".join(target_import_string))
+            vendor_targets.append("\n".join(target_import_string))
 
             # 10. Create a versionless alias target
             #
@@ -346,6 +350,9 @@ def _generate_imports(repository_ctx, dep_tree, explicit_artifacts, neverlink_ar
             versioned_target_alias_label = escape(strip_packaging_and_classifier(artifact["coord"]))
             all_imports.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)
+            all_imports.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.
@@ -359,6 +366,9 @@ def _generate_imports(repository_ctx, dep_tree, explicit_artifacts, neverlink_ar
             if repository_ctx.attr.maven_install_json:
                 all_imports.append(_genrule_copy_artifact_from_http_file(artifact, default_visibilities))
 
+            # 12. collect the artifact_path for the filegroup rule collecting all necessary sources for vendoring
+            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
@@ -410,7 +420,10 @@ def _generate_imports(repository_ctx, dep_tree, explicit_artifacts, neverlink_ar
             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\"", "\"WORKSPACE\""] + artifact_paths)))
+
+    return ("\n".join(all_imports), jar_versionless_target_labels, "\n".join(vendor_targets))
 
 parser = struct(
     generate_imports = _generate_imports,