feat(internal/kokoro): add script to test compatibility with samples

internal/kokoro/build_samples.sh

@@ -0,0 +1,66 @@
+#!/bin/bash
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License..
+
+# Fail on any error
+set -eo pipefail
+
+# Display commands being run
+set -x
+
+# Where google-cloud-go code is located.
+gcwd=$PWD/github/google-cloud-go
+
+cd github/golang-samples
+
+# Returns 0 if the test should be skipped because the current Go
+# version is too old for the current module.
+goVersionShouldSkip() {
+  echo "Downloading modules and checking versions"
+  modVersion="$(go list -m -f '{{.GoVersion}}')"
+  if [ -z "$modVersion" ]; then
+    # Not in a module or minimum Go version not specified, don't skip.
+    return 1
+  fi
+
+  go list -f "{{context.ReleaseTags}}" | grep -q -v "go$modVersion\b"
+}
+
+# For each module, build the code with local google-cloud-go changes.
+for i in $(find . -name go.mod); do
+  # internal: this does not need to be built to test compatibility
+  # run/events_pubsub: module requires go1.13 for cloudevents
+  if [[ $i == *"/internal/"* ]]; then
+    continue
+  fi
+
+  pushd $(dirname $i)
+  if goVersionShouldSkip; then
+    popd
+    continue
+  fi
+  # TODO(codyoss): if we spilt out modules someday we should make this programmatic.
+  go mod edit -replace cloud.google.com/go=$gcwd
+  go mod edit -replace cloud.google.com/go/bigtable=$gcwd/bigtable
+  go mod edit -replace cloud.google.com/go/bigquery=$gcwd/bigquery
+  go mod edit -replace cloud.google.com/go/datastore=$gcwd/datastore
+  go mod edit -replace cloud.google.com/go/firestore=$gcwd/firestore
+  go mod edit -replace cloud.google.com/go/logging=$gcwd/logging
+  go mod edit -replace cloud.google.com/go/pubsub=$gcwd/pubsub
+  go mod edit -replace cloud.google.com/go/spanner=$gcwd/spanner
+  go mod edit -replace cloud.google.com/go/storage=$gcwd/storage
+  echo "Building module $i"
+  go build ./...
+  popd
+done