feat: add example with go proto codegen

.bazelrc

@@ -1,4 +1,8 @@
 import %workspace%/tools/preset.bazelrc
+common --@protobuf//bazel/toolchains:prefer_prebuilt_protoc
+
+# Cause a build failure when files in the source tree don't match their generated counterparts.
+common --@diff.bzl//diff:validate_diffs
 
 # Don’t want to push a rules author to update their deps if not needed.
 # https://bazel.build/reference/command-line-reference#flag--check_direct_dependencies

.github/workflows/ci.yaml

@@ -13,6 +13,11 @@ concurrency:
   # See https://docs.github.com/en/actions/using-jobs/using-concurrency and https://docs.github.com/en/actions/learn-github-actions/contexts for more info.
   group: concurrency-group::${{ github.workflow }}::${{ github.event.pull_request.number > 0 && format('pr-{0}', github.event.pull_request.number) || github.ref_name }}${{ github.ref_name == 'main' && format('::{0}', github.run_id) || ''}}
   cancel-in-progress: ${{ github.ref_name != 'main' }}
+
+permissions:
+  contents: write
+  pull-requests: write
+
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -29,8 +34,27 @@ jobs:
       USE_BAZEL_VERSION: ${{ matrix.bazel }}
     steps:
       - uses: actions/checkout@v5
+        with:
+          # Important: checkout the PR HEAD ref so we can push commits to it.
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          fetch-depth: 0
       - uses: bazel-contrib/setup-bazel@0.18.0
+        with:
+          # just needed for Bazel 8 performance
+          bazelrc: common --incompatible_enable_proto_toolchain_resolution
       - run: bazel test //...
+      # Simulate what Aspect Workflows could do
+      # Run the build with patches requested, then apply them and run the tests again
+      - if: failure()
+        run: |
+          ./examples/test.sh //examples/...
+          git config --global user.email "marvin@aspect.build"
+          git config --global user.name "Marvin [bot]"
+          git commit -a -m "fix: apply patches"
+          git push origin "HEAD:${{ github.event.pull_request.head.ref }}"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   pre-commit:
     runs-on: ubuntu-latest

MODULE.bazel

@@ -14,6 +14,8 @@ bazel_dep(name = "bazel_lib", version = "3.0.0")
 bazel_dep(name = "diffutils", version = "3.12", dev_dependency = True)
 bazel_dep(name = "buildifier_prebuilt", version = "8.2.1", dev_dependency = True)
 bazel_dep(name = "bazelrc-preset.bzl", version = "1.6.0", dev_dependency = True)
+bazel_dep(name = "protobuf", version = "33.4", dev_dependency = True)
+bazel_dep(name = "rules_go", version = "0.60.0", dev_dependency = True)
 
 register_toolchains(
     "//tools/toolchains:all",

diff/private/diff.bzl

@@ -66,12 +66,11 @@ def _diff_rule_impl(ctx):
 
     # If both inputs are generated, there's no writable file to patch.
     is_copy_to_source = ctx.file.file1.is_source or ctx.file.file2.is_source
-    outputs = [ctx.outputs.patch, ctx.outputs.exit_code]
     ctx.actions.run_shell(
         inputs = [ctx.file.file1, ctx.file.file2] + diffinfo.tool_files,
-        outputs = outputs,
+        outputs = [ctx.outputs.patch, ctx.outputs.exit_code],
         command = command,
-        mnemonic = "DiffutilsDiff",
+        mnemonic = "Diff",
         progress_message = "Diffing %{input} to %{output}",
     )
 
@@ -82,11 +81,11 @@ def _diff_rule_impl(ctx):
         ERROR: diff command exited with non-zero status.
 
         To accept the diff, run:
-        patch -d \\$(bazel info workspace) -p0 < {patch}
-        """.format(patch = ctx.outputs.patch.path)))
+        patch -d \\$(bazel info workspace) -p0 < \\$(bazel info bazel-bin)/{patch}
+        """.format(patch = ctx.outputs.patch.short_path)))
 
     return [
-        DefaultInfo(files = depset(outputs)),
+        DefaultInfo(files = depset([ctx.file.file1])),
         OutputGroupInfo(
             _validation = depset(validation_outputs),
             # By reading the Build Events, a Bazel wrapper can identify this diff output group and apply the patch.