Add build test for Flutter codelabs (#19579)

* Add build test for Flutter codelabs

* Fix indentation in build test script

* Correct filename for the codelabs build test run by travis

* Change if statement to elif

* Replace echo statements with set -x

* Add BSD-style license

* Add codelabs build test to Cirrus

* Remove codelabs_build_test from Travis.

* Remove codelabs_build_test from travis_script.sh

* Update documentation for codelabs_build_test.sh

* Update readme for build test

* Add link to open a new issue to MDC-Flutter

* Add phrase to address "if you think you really need to break this test, please escalate this"

.cirrus.yml

@@ -61,6 +61,11 @@ task:
       container:
         cpu: 4
         memory: 8G
+    - name: codelabs-build-test
+      env:
+        SHARD: codelabs-build-test
+      build_test_script: ./dev/bots/codelabs_build_test.sh
+
 
 task:
   windows_container:

dev/bots/README.md

@@ -148,3 +148,17 @@ components need to be updated or installed, follow the steps below:
 6. Run upload_android_tools.py -t ndk
    `$ cd ../..`
    `$ dev/bots/upload_android_tools.py -t ndk`
+
+## Flutter codelabs build test
+
+The Flutter codelabs exercise Material Components in the form of a demo application. Note that the 
+code for the codelabs is similar to but distinct from the code for the Shrine demo app in Flutter Gallery.
+The Flutter codelabs build test ensures that the final version of
+[Material Components for Flutter Codelabs](https://github.com/material-components/material-components-flutter-codelabs)
+can be built. This test serves as a smoke test for the Flutter framework and should not fail. Please
+address the issue from within your PR and rerun the test. If you feel that the test failing is not a
+direct result of changes made in your PR or that breaking this test is absolutely necessary, escalate this issue by
+[submitting an issue](https://github.com/material-components/material-components-flutter-codelabs/issues/new?title=%5BURGENT%5D%20Flutter%20Framework%20breaking%20PR)
+to the MDC-Flutter Team.
+
+

dev/bots/codelabs_build_test.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+# Copyright 2018 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+
+set -ex
+
+readonly SCRIPTS_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+readonly ROOT_DIR="$SCRIPTS_DIR/.."
+
+function is_expected_failure() {
+  # A test target was specified with the 'build' command.
+  grep --quiet "is not configured for Running" "$1"
+}
+
+log_file="build_log_for_104_complete.txt"
+build_command="flutter build bundle"
+
+# Attempt to build 104-complete Shrine app from the Flutter codelabs
+git clone https://github.com/material-components/material-components-flutter-codelabs.git
+cd material-components-flutter-codelabs/mdc_100_series/
+git checkout 104-complete
+
+all_builds_ok=1
+echo "$build_command"
+$build_command 2>&1 | tee "$log_file"
+
+if [ ${PIPESTATUS[0]} -eq 0 ] || is_expected_failure "$log_file"; then
+  rm "$log_file"
+else
+  all_builds_ok=0
+  echo "View https://github.com/flutter/flutter/blob/master/dev/bots/README.md for steps to resolve this failed build test." >> ${log_file}
+  echo
+  echo "Log left in $log_file."
+  echo
+fi
+
+# If any build failed, exit with a failure exit status so continuous integration
+# tools can react appropriately.
+if [ "$all_builds_ok" -eq 1 ]; then
+  exit 0
+else
+  exit 1
+fi