From a34ad7790416dac4680e201d00f95be37b5de93c Mon Sep 17 00:00:00 2001
From: Cody Oss <6331106+codyoss@users.noreply.github.com>
Date: Fri, 15 Sep 2023 12:02:14 -0500
Subject: [PATCH] feat(internal): add some feature flags for new auth libs
 (#2163)

We will use the internaloption to start to enable new auth lib for a small number of clients in the future. The envvar will be undocumented and used exclusively in our own testing environments. We will enable it on all of our repos as the first part of functional testing that all existing integration tests continue to work as normal when routing through the new auth layers.
---
 internal/settings.go                    | 17 +++++++++++++++++
 option/internaloption/internaloption.go | 13 +++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/internal/settings.go b/internal/settings.go
index 3a3874df112..84f9302dcfa 100644
--- a/internal/settings.go
+++ b/internal/settings.go
@@ -9,6 +9,8 @@ import (
 	"crypto/tls"
 	"errors"
 	"net/http"
+	"os"
+	"strconv"
 
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
@@ -16,6 +18,10 @@ import (
 	"google.golang.org/grpc"
 )
 
+const (
+	newAuthLibEnVar = "GOOGLE_API_GO_EXPERIMENTAL_USE_NEW_AUTH_LIB"
+)
+
 // DialSettings holds information needed to establish a connection with a
 // Google API service.
 type DialSettings struct {
@@ -47,6 +53,7 @@ type DialSettings struct {
 	ImpersonationConfig           *impersonate.Config
 	EnableDirectPath              bool
 	EnableDirectPathXds           bool
+	EnableNewAuthLibrary          bool
 	AllowNonDefaultServiceAccount bool
 
 	// Google API system parameters. For more information please read:
@@ -77,6 +84,16 @@ func (ds *DialSettings) HasCustomAudience() bool {
 	return len(ds.Audiences) > 0
 }
 
+func (ds *DialSettings) IsNewAuthLibraryEnabled() bool {
+	if ds.EnableNewAuthLibrary {
+		return true
+	}
+	if b, err := strconv.ParseBool(os.Getenv(newAuthLibEnVar)); err == nil {
+		return b
+	}
+	return false
+}
+
 // Validate reports an error if ds is invalid.
 func (ds *DialSettings) Validate() error {
 	if ds.SkipValidation {
diff --git a/option/internaloption/internaloption.go b/option/internaloption/internaloption.go
index 3b8461d1da9..b2b249eec68 100644
--- a/option/internaloption/internaloption.go
+++ b/option/internaloption/internaloption.go
@@ -150,6 +150,19 @@ func (w *withCreds) Apply(o *internal.DialSettings) {
 	o.InternalCredentials = (*google.Credentials)(w)
 }
 
+// EnableNewAuthLibrary returns a ClientOption that specifies if libraries in this
+// module to delegate auth to our new library. This option will be removed in
+// the future once all clients have been moved to the new auth layer.
+func EnableNewAuthLibrary() option.ClientOption {
+	return enableNewAuthLibrary(true)
+}
+
+type enableNewAuthLibrary bool
+
+func (w enableNewAuthLibrary) Apply(o *internal.DialSettings) {
+	o.EnableNewAuthLibrary = bool(w)
+}
+
 // EmbeddableAdapter is a no-op option.ClientOption that allow libraries to
 // create their own client options by embedding this type into their own
 // client-specific option wrapper. See example for usage.