Add support for repo_contents_cache (#15)

Author: malt3

gcs/private/BUILD.bazel

@@ -24,6 +24,7 @@ bzl_library(
         "//docs:__pkg__",
         "//gcs/private:__subpackages__",
     ],
+    deps = ["@bazel_tools//tools/build_defs/repo:utils.bzl"],
 )
 
 filegroup(

gcs/private/repo_rules/eager.bzl

@@ -24,7 +24,9 @@ def _eager_impl(repository_ctx):
 
     # start downloads
     waiters = []
+    reproducible = True
     for local_path, info in deps.items():
+        reproducible = reproducible and info_is_reproducible(info)
         args = info_to_download_args(repository_ctx.attr.bucket, local_path, info)
         waiters.append(repository_ctx.download(**args))
 
@@ -36,6 +38,11 @@ def _eager_impl(repository_ctx):
         for waiter in waiters:
             waiter.wait()
 
+    if hasattr(repository_ctx, "repo_metadata"):
+        # allows participating in repo contents cache
+        return repository_ctx.repo_metadata(reproducible = reproducible)
+    return None
+
 def info_to_download_args(bucket_name, local_path, info):
     args = {
         "url": bucket_url(bucket_name, info["remote_path"]),
@@ -51,6 +58,10 @@ def info_to_download_args(bucket_name, local_path, info):
         args["integrity"] = info["integrity"]
     return args
 
+def info_is_reproducible(info):
+    digest = info.get("sha256") or info.get("integrity")
+    return len(digest) > 0
+
 eager = repository_rule(
     implementation = _eager_impl,
     attrs = {

gcs/private/repo_rules/gcs_archive.bzl

@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 """
 
-load("//gcs/private:util.bzl", "bucket_url", "download_and_extract_args", "parse_gs_url")
+load("//gcs/private:util.bzl", "download_and_extract_args", "parse_gs_url", "update_integrity_attr")
 
 def _gcs_archive_impl(repository_ctx):
     gs_url = repository_ctx.attr.url
@@ -24,7 +24,7 @@ def _gcs_archive_impl(repository_ctx):
 
     # download && extract the repo
     args = download_and_extract_args(repository_ctx.attr, target["bucket_name"], target["remote_path"])
-    repository_ctx.download_and_extract(**args)
+    download_info = repository_ctx.download_and_extract(**args)
 
     # apply patches after extraction has finished
     for patch in repository_ctx.attr.patches:
@@ -39,6 +39,7 @@ def _gcs_archive_impl(repository_ctx):
         repository_ctx.file("BUILD.bazel", repository_ctx.attr.build_file_content)
     if has_build_file_label:
         repository_ctx.file("BUILD.bazel", repository_ctx.read(repository_ctx.attr.build_file))
+    return update_integrity_attr(repository_ctx, _gcs_archive_attrs, download_info)
 
 _gcs_archive_doc = """Downloads a Bazel repository as a compressed archive file from a GCS bucket, decompresses it,
 and makes its targets available for binding.

gcs/private/repo_rules/gcs_file.bzl

@@ -15,8 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 """
 
-load("//gcs/private:url_encoding.bzl", "url_encode")
-load("//gcs/private:util.bzl", "bucket_url", "download_args", "parse_gs_url", "have_unblocked_downloads")
+load("//gcs/private:util.bzl", "download_args", "parse_gs_url", "have_unblocked_downloads", "update_integrity_attr")
 
 def _gcs_file_impl(repository_ctx):
     gs_url = repository_ctx.attr.url
@@ -26,6 +25,7 @@ def _gcs_file_impl(repository_ctx):
     # start download
     args = download_args(repository_ctx.attr, target["bucket_name"], target["remote_path"])
     waiter = repository_ctx.download(**args)
+    download_info = waiter
 
     # populate BUILD files
     repository_ctx.file("BUILD.bazel", "exports_files(glob([\"**\"]))".format(args["output"]))
@@ -36,7 +36,8 @@ def _gcs_file_impl(repository_ctx):
 
     # wait for download to finish
     if have_unblocked_downloads():
-        waiter.wait()
+        download_info = waiter.wait()
+    return update_integrity_attr(repository_ctx, _gcs_file_attrs, download_info)
 
 _gcs_file_doc = """Downloads a file from a GCS bucket and makes it available to be used as a file group.
 

gcs/private/util.bzl

@@ -15,6 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 """
 
+load("@bazel_tools//tools/build_defs/repo:utils.bzl", "update_attrs")
 load("//gcs/private:jsonpath.bzl", "walk_jsonpath")
 load("//gcs/private:url_encoding.bzl", "url_encode")
 
@@ -141,3 +142,13 @@ def have_unblocked_downloads():
     if version[0] == 7 and version[1] < 1:
         return False
     return True
+
+def update_integrity_attr(ctx, attrs, download_info):
+    if not hasattr(ctx, "repo_metadata"):
+        # Old Bazel versions do not support repo_metadata
+        return None
+    # We don't need to override the integrity attribute if sha256 is already specified.
+    if ctx.attr.sha256 or ctx.attr.integrity:
+        return ctx.repo_metadata(reproducible = True)
+    integrity_override = {"integrity": download_info.integrity}
+    return ctx.repo_metadata(attrs_for_reproducibility = update_attrs(ctx.attr, attrs.keys(), integrity_override))