chore: add apidiff to showcase test (#730)

.github/workflows/ci.yaml

@@ -66,15 +66,26 @@ jobs:
         sudo ln -s /usr/src/protoc/bin/protoc /usr/local/bin/protoc
     - name: Install tools and dependencies
       run: |
+        go install golang.org/x/exp/cmd/apidiff
         go install github.com/golang/protobuf/protoc-gen-go
         curl -sSL https://github.com/googleapis/googleapis/archive/master.zip > googleapis.zip
         unzip googleapis.zip -x "googleapis-master/google/ads/*"
         mv googleapis-master /tmp/googleapis
+    - name: Create Go package API baseline
+      if: "!contains(github.event.pull_request.labels.*.name, 'breaking change allowed')"
+      run: |
+        cd showcase
+        apidiff -w pkg.latest github.com/googleapis/gapic-showcase/client
     - name: Run integration tests
       run: |
         export PATH=$PATH:protobuf/bin
         export GOOGLEAPIS=/tmp/googleapis
         make test
+    - name: Compare regenerated code to baseline
+      if: "!contains(github.event.pull_request.labels.*.name, 'breaking change allowed')"
+      run: |
+        cd showcase
+        apidiff -incompatible pkg.latest github.com/googleapis/gapic-showcase/client > diff.txt && cat diff.txt && ! [ -s diff.txt ]
   bazel-build:
     runs-on: ubuntu-latest
     container: gcr.io/gapic-images/googleapis:latest

showcase/showcase.bash

@@ -39,7 +39,12 @@ protoc \
 	--go_gapic_opt 'grpc-service-config=showcase_grpc_service_config.json' \
 	--go_gapic_opt 'api-service-config=showcase_v1beta1.yaml' \
 	--descriptor_set_in=<(curl -sSL https://github.com/googleapis/gapic-showcase/releases/download/v$SHOWCASE_SEMVER/gapic-showcase-$SHOWCASE_SEMVER.desc) \
-	google/showcase/v1beta1/echo.proto google/showcase/v1beta1/identity.proto google/showcase/v1beta1/sequence.proto google/showcase/v1beta1/compliance.proto
+	google/showcase/v1beta1/echo.proto \
+	google/showcase/v1beta1/identity.proto \
+	google/showcase/v1beta1/sequence.proto \
+	google/showcase/v1beta1/testing.proto \
+	google/showcase/v1beta1/messaging.proto \
+	google/showcase/v1beta1/compliance.proto
 
 hostos=$(go env GOHOSTOS)
 hostarch=$(go env GOHOSTARCH)