vendoring.bzl: Adding a way to dynamically choose whether to use vend…

…ored repo or pull it from git.

Needed to build in environments that do not support git submodules, because all our vendored repos are actually not vendored, but are submodules.

Currently not used for any of the packages we have.

WORKSPACE

@@ -1,6 +1,8 @@
 # -*-Python-*-
 workspace(name="yatc")
 
+load(":vendoring.bzl", "vendored_git_repository", "new_vendored_git_repository")
+
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 local_repository(

vendoring.bzl

@@ -0,0 +1,66 @@
+# -*- mode: python; -*-
+# vim: set syntax=python:
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository", "new_git_repository")
+
+def _vendored_git_repository_impl(repository_ctx):
+  url = repository_ctx.attr.url
+  schemaless_url = url.split("://", 1)[1]
+  local_path = repository_ctx.workspace_root.get_child("vendor", schemaless_url)
+  if local_path.get_child("WORKSPACE").exists or local_path.get_child("WORKSPACE.bazel").exists:
+    # git submodule init --update was run.
+
+    if repository_ctx.attr.build_file_content:
+      native.new_local_repository(
+        name = repository_ctx.attr.name,
+        path = local_path,
+        build_file_content = repository_ctx.attr.build_file_content,
+      )
+    else:
+      native.local_repository(
+        name = repository_ctx.attr.name,
+        path = local_path,
+      )
+  else:
+    # Vendored path is not a valid Bazel repo
+    # Assume it's a submodule for now.
+    # TODO: read .gitmodules to avoid the need for commit to be passed, and to detect an invalid submodule being defined.
+    # TODO: if github, fetch with http_archive / http_file.
+
+    if repository_ctx.attr.build_file_content:
+      new_git_repository(
+        name = repository_ctx.attr.name,
+        url = repository_ctx.attr.url,
+        commit = repository_ctx.attr.commit,
+        tag = repository_ctx.attr.tag,
+        build_file_content = repository_ctx.attr.build_file_content,
+      )
+    else:
+      git_repository(
+        name = repository_ctx.attr.name,
+        url = repository_ctx.attr.url,
+        commit = repository_ctx.attr.commit,
+        tag = repository_ctx.attr.tag,
+      )
+
+
+_vendored_git_repository_rule = repository_rule(
+  implementation = _vendored_git_repository_impl,
+  attrs = {
+    "url": attr.string(),
+    # "sha256": attr.string(), # Only applicable if we use http_archive.
+    "commit": attr.string(),
+    "tag": attr.string(),
+
+    "build_file_content": attr.string(), # If empty, assume not new_*_repository.
+  },
+)
+
+
+def vendored_git_repository(name, url, commit = None, tag = None):
+  _vendored_git_repository_rule(name = name, url = url, commit = commit, tag = tag)
+
+
+def new_vendored_git_repository(name, url, build_file_content, commit = None, tag = None):
+  _vendored_git_repository_rule(name = name, url = url, commit = commit, tag = tag, build_file_content = build_file_content)