test.bash: do not run golden tests by default

The golden tests are sensitive to the exact version used:
* Protobuf toolchain since the generated Descriptor is dependendent on protoc
(for example, default json_names were auto-populated in later versions of protoc)
* Go toolchain since the generated .pb.go files is dependent on the exact output
of gofmt and the gzip compression used.

There are other areas where it depends on unstable output, but the above are the
major causes.

Since test.bash ensures that the golden tests are run with exact versions of the
protobuf and Go toolchains, we can ensure that the tests are reproducible across
different developer workstations.

Thus, we add a "golden" build tag to disable them for normal invocations of
"go test ./..." and only run them if test.bash is run.

If test.bash is ever updated with newer versions, the golden testdata can be
updated at the same time.

Change-Id: Ia2b7b039aad2ddaef7652e332215bf9403a6d856
Reviewed-on: https://go-review.googlesource.com/c/142458
Reviewed-by: Damien Neil <dneil@google.com>

cmd/protoc-gen-go-grpc/golden_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !race
+// +build golden
 
 package main
 

cmd/protoc-gen-go/golden_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !race
+// +build golden
 
 package main
 

protogen/protogen_test.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// +build golden
+
 package protogen
 
 import (

test.bash

@@ -85,11 +85,16 @@ for GO_VERSION in ${GO_VERSIONS[@]}; do
 	}
 
 	go build ./...
-	go test ./...
 	go test -race ./...
 	go test -race -tags purego ./...
 	go test -race -tags proto1_legacy ./...
 
+	# Only run golden tests with the latest Go version since
+	# the test results are sensitive to the exact version used.
+	if [ $GO_VERSION = $GO_LATEST ]; then
+		go test -tags golden ./...
+	fi
+
 	unset go # to avoid confusing later invocations of "go"
 done