test: setup showcase testing for codegen modules (#1957)

An initial setup for testing spring-cloud-generator using showcase:
* setup-showcase.sh: script to generate starter module for gapic-showcase: showcase-spring-starter
    - Two options: verify (default, used by the gh actions workflow) and update (-u flag, for updating “golden” showcase module in development of spring generator)
* EchoAutoConfigurationTests: handwritten unit tests to migrate/replace existing coverage in LanguageAutoConfigurationTests (currently living alongside spring-cloud-previews/google-cloud-language-starter)
* showcaseTests.yaml: new CI workflow to run showcase verification (generation diff from goldens, compile with handwritten unit tests) for spring-cloud-generator

.github/workflows/showcaseTests.yaml

@@ -0,0 +1,51 @@
+name: Generator - Showcase Tests
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    paths:
+      - 'spring-cloud-generator/**'
+  workflow_dispatch:
+
+jobs:
+  showcaseTests:
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Java 17
+        uses: actions/setup-java@v1
+        with:
+          java-version: 17
+      - name: Install buildozer
+        run: |
+          go install github.com/bazelbuild/buildtools/buildozer@latest
+          export PATH=$PATH:$(go env GOPATH)/bin
+          buildozer --version
+      - name: Install spring-cloud-gcp
+        # Installs spring-cloud-gcp from root,
+        # including spring-cloud-generator module
+        run: |
+          ./mvnw \
+            --batch-mode \
+            --show-version \
+            --threads 1.5C \
+            --define maven.test.skip=true \
+            --define maven.javadoc.skip=true \
+            install
+      - name: Verify generation of showcase-spring-starter
+        # Runs showcase-spring-starter golden tests
+        working-directory: spring-cloud-generator
+        id: verify-showcase-spring-starter
+        run: |
+          set -x
+          set -e
+          export PATH=$PATH:$(go env GOPATH)/bin
+          buildozer --version
+          bash scripts/generate-showcase.sh
+      - name: Unit tests for showcase-spring-starter
+        # Runs showcase-spring-starter unit tests
+        working-directory: spring-cloud-generator
+        run: |
+          cd showcase/showcase-spring-starter && mvn verify

spring-cloud-generator/README.md

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+# Generator - Spring Boot Starters for Google Client Libraries
+
+
+## Development Workflow
+
+For local development in the `spring-cloud-generator` submodule,
+first build `spring-cloud-gcp` from root:
+
+```
+mvn clean install -DskipTests
+```
+
+### Generation of Spring Boot Starters
+
+Corresponding workflow file: [generateAutoConfigs.yml](/.github/workflows/generateAutoConfigs.yml)
+
+Script: [generate.sh](scripts/generate.sh)
+
+Requirements (to run commands below):
+* Java 17
+* [bazelisk](https://github.com/bazelbuild/bazelisk)
+* [buildozer](https://github.com/bazelbuild/buildtools/tree/master/buildozer)
+* [jq](https://jqlang.github.io/jq/download/)
+* [xmllint](https://gnome.pages.gitlab.gnome.org/libxml2/xmllint.html)
+* For MacOS, set up [gnu-sed](https://formulae.brew.sh/formula/gnu-sed) to use as `sed`
+
+To execute the generation process locally, run (from the `spring-cloud-generator` directory):
+```
+bash scripts/generate.sh
+```
+
+### Showcase Testing for the Generator
+
+Corresponding workflow file: [showcaseTests.yml](/.github/workflows/showcaseTests.yml)
+
+Script: [generate-showcase.sh](scripts/generate-showcase.sh)
+
+Requirements (to run commands below):
+* Java 17
+* [bazelisk](https://github.com/bazelbuild/bazelisk)
+* [buildozer](https://github.com/bazelbuild/buildtools/tree/master/buildozer)
+* For MacOS, set up [gnu-sed](https://formulae.brew.sh/formula/gnu-sed) to use as `sed`
+
+To execute showcase golden tests locally, run (from the `spring-cloud-generator` directory):
+```
+bash scripts/generate-showcase.sh
+```
+* This runs the generator for showcase clients and compares its output against the expected golden `showcase-spring-starter` module. 
+
+To update showcase golden tests locally, run ((from the `spring-cloud-generator` directory):
+```
+bash scripts/generate-showcase.sh -u
+```
+* This runs the generator for showcase clients and overwrites the golden module `showcase-spring-starter`.
+
+To execute showcase unit tests locally, run (from the `spring-cloud-generator` directory):
+```
+cd showcase/showcase-spring-starter && mvn verify
+```
+* This compiles the generated `showcase-spring-starter` module and runs handwritten unit tests under `showcase-spring-starter/test`.

spring-cloud-generator/scripts/generate-showcase.sh

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+#!/bin/bash
+
+# To VERIFY: ./scripts/generate-showcase.sh
+# To UPDATE: /scripts/generate-showcase.sh -u
+UPDATE=0
+while getopts u flag
+do
+    case "${flag}" in
+        u) UPDATE=1;;
+    esac
+done
+
+# For reusing bazel setup modifications and post-processing steps
+source ./scripts/generate-steps.sh
+
+# If not set, assume working directory is spring-cloud-generator
+if [[ -z "$SPRING_GENERATOR_DIR" ]]; then
+  SPRING_GENERATOR_DIR=`pwd`
+fi
+SPRING_ROOT_DIR=${SPRING_GENERATOR_DIR}/..
+SHOWCASE_STARTER_OLD_DIR=${SPRING_GENERATOR_DIR}/showcase/showcase-spring-starter
+SHOWCASE_STARTER_NEW_DIR=${SPRING_GENERATOR_DIR}/showcase/showcase-spring-starter-generated
+
+# Verifies newly generated showcase-spring-starter against goldens
+#
+# $1 - directory containing existing showcase-spring-starter (golden)
+# $2 - directory containing newly generated showcase-spring-starter
+function verify(){
+  OLD_DIR=$1
+  NEW_DIR=$2
+  SHOWCASE_STARTER_DIFF=$(diff -r ${NEW_DIR}/src/main ${OLD_DIR}/src/main)
+  SHOWCASE_STARTER_POM_DIFF=$(diff -r ${NEW_DIR}/pom.xml ${OLD_DIR}/pom.xml)
+  if [ "$SHOWCASE_STARTER_DIFF" != "" ] || [ "$SHOWCASE_STARTER_POM_DIFF" != "" ]
+  then
+      echo "Differences detected in generated showcase starter module: "
+      echo "Diff from src/main: "
+      echo $SHOWCASE_STARTER_DIFF
+      echo "Diff from pom.xml: "
+      echo $SHOWCASE_STARTER_POM_DIFF
+      exit 1;
+  else
+      echo "No differences found in showcase-spring-starter"
+      rm -r ${NEW_DIR}
+  fi
+}
+
+# Setup, generation, and post-processing steps for showcase-spring-starter
+#
+# $1 - target directory for generated starter
+function generate_showcase_spring_starter(){
+  SHOWCASE_STARTER_DIR=$1
+
+  # Compute the parent project version.
+  cd ${SPRING_ROOT_DIR}
+  PROJECT_VERSION=$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout)
+  cd ${SPRING_GENERATOR_DIR}
+  GAPIC_GENERATOR_JAVA_VERSION=$(mvn help:evaluate -Dexpression=gapic-generator-java-bom.version -q -DforceStdout)
+
+  # Clone sdk-platform-java (with showcase library)
+  git clone https://github.com/googleapis/sdk-platform-java.git
+  git checkout "v${GAPIC_GENERATOR_JAVA_VERSION}"
+
+  # Install showcase client libraries locally
+  cd sdk-platform-java && mvn clean install -B -ntp -DskipTests -Dclirr.skip -Dcheckstyle.skip
+  cd showcase && mvn clean install
+  GAPIC_SHOWCASE_CLIENT_VERSION=$(mvn help:evaluate -Dexpression=project.version -q -DforceStdout)
+
+  # Alternative: if showcase client library is available on Maven Central,
+  # Instead of downloading sdk-platform-java/showcase (for client library, and generation setup),
+  # Can instead download googleapis (for generation setup) and gapic-showcase (for protos)
+
+  # Modify sdk-platform-java/WORKSPACE
+  modify_workspace_file "../WORKSPACE" ".." "../../scripts/resources/googleapis_modification_string.txt"
+  # Modify sdk-platform-java/showcase/BUILD.bazel
+  buildozer 'new_load @spring_cloud_generator//:java_gapic_spring.bzl java_gapic_spring_library' BUILD.bazel:__pkg__
+  modify_build_file "BUILD.bazel"
+
+  # Invoke bazel target for generating showcase-spring-starter
+  bazelisk build --tool_java_language_version=17 --tool_java_runtime_version=remotejdk_17 //showcase:showcase_java_gapic_spring
+
+  # Post-process generated modules
+  copy_and_unzip "../bazel-bin/showcase/showcase_java_gapic_spring-spring.srcjar" "showcase_java_gapic_spring-spring.srcjar" "${SPRING_GENERATOR_DIR}/showcase" ${SHOWCASE_STARTER_DIR}
+  modify_starter_pom ${SHOWCASE_STARTER_DIR}/pom.xml "com.google.cloud" "gapic-showcase" $PROJECT_VERSION
+
+  # Additional pom.xml modifications for showcase starter
+  # Add explicit gapic-showcase version
+  sed -i '/^ *<artifactId>gapic-showcase<\/artifactId>*/a \ \ \ \ \ \ <version>'"$GAPIC_SHOWCASE_CLIENT_VERSION"'</version>' ${SHOWCASE_STARTER_DIR}/pom.xml
+  # Update relative path to parent pom (different repo structure from starters)
+  RELATIVE_PATH="\ \ \ \ <relativePath>..\/..\/..\/spring-cloud-gcp-starters\/pom.xml<\/relativePath>"
+  sed -i 's/^ *<relativePath>.*/'"$RELATIVE_PATH"'/g' ${SHOWCASE_STARTER_DIR}/pom.xml
+
+  # Run google-java-format on generated code
+  run_formatter ${SHOWCASE_STARTER_DIR}
+
+  # Remove downloaded repos
+  rm -rf ${SPRING_GENERATOR_DIR}/sdk-platform-java
+}
+
+if [[ UPDATE -ne 0 ]]; then
+    echo "Running script to perform showcase-spring-starter update"
+    generate_showcase_spring_starter ${SHOWCASE_STARTER_OLD_DIR}
+  else
+    echo "Running script to perform showcase-spring-starter verification"
+    generate_showcase_spring_starter ${SHOWCASE_STARTER_NEW_DIR}
+    verify ${SHOWCASE_STARTER_OLD_DIR} ${SHOWCASE_STARTER_NEW_DIR}
+fi