Collect code coverage stats on Travis (#2913)

This currently only working for the main Firebase Example on iOS.

Author: Corrob

scripts/build.sh

@@ -188,6 +188,9 @@ case "$product-$method-$platform" in
         test
 
     if [[ $platform == 'iOS' ]]; then
+      # Code Coverage collection is only working on iOS currently.
+      ./scripts/collect_metrics.sh 'Example/Firebase.xcworkspace' "AllUnitTests_$platform"
+
       # Run integration tests (not allowed on PRs)
       if [ "$TRAVIS_PULL_REQUEST" == "false" ]; then
         RunXcodebuild \

scripts/collect_metrics.sh

@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+
+# Copyright 2019 Google
+#
+# 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.
+
+# USAGE: ./collect_metrics.sh workspace scheme
+#
+# Collects project health metrics and uploads them to a database. Currently just collects code
+# coverage for the provided workspace and scheme. Assumes that those tests have already been
+# executed.
+
+set -euo pipefail
+
+if [[ $# -ne 2 ]]; then
+  cat 1>&2 <<EOF
+USAGE: $0 workspace scheme
+
+Collects project health metrics and uploads them to a database. Currently just collects code
+coverage for the provided workspace and scheme. Assumes that those tests have already been
+executed.
+EOF
+  exit 1
+fi
+
+if [[ ! -z "${TRAVIS_PULL_REQUEST}" ]]; then
+  WORKSPACE="$1"
+  SCHEME="$2"
+
+  gem install xcov
+  xcov --workspace "${WORKSPACE}" --scheme "${SCHEME}" --output_directory Metrics --json_report
+  cd Metrics
+  swift build
+  .build/debug/Metrics -c report.json -p "${TRAVIS_PULL_REQUEST}"
+  cd ..
+fi