Add additional documentation in metrics proto regen.sh script.
Added additional instruction in the regen.sh script to build the
blueprint_tools and aprotoc in case the regen.sh script fails.
Bug: b/169395325
Test: ./regen.sh
Change-Id: Icb38c907fb47febc17eef1067d06d0588dd0b7ba
diff --git a/ui/metrics/metrics_proto/regen.sh b/ui/metrics/metrics_proto/regen.sh
index 343c638..8eb2d74 100755
--- a/ui/metrics/metrics_proto/regen.sh
+++ b/ui/metrics/metrics_proto/regen.sh
@@ -1,3 +1,17 @@
#!/bin/bash
-aprotoc --go_out=paths=source_relative:. metrics.proto
+# Generates the golang source file of metrics.proto protobuf file.
+
+set -e
+
+function die() { echo "ERROR: $1" >&2; exit 1; }
+
+readonly error_msg="Maybe you need to run 'lunch aosp_arm-eng && m aprotoc blueprint_tools'?"
+
+if ! hash aprotoc &>/dev/null; then
+ die "could not find aprotoc. ${error_msg}"
+fi
+
+if ! aprotoc --go_out=paths=source_relative:. metrics.proto; then
+ die "build failed. ${error_msg}"
+fi