feat(spanner): configurable logger (#6958)

Expose logger in ClientConfig so consumers can set a logger.

This is useful when using spannertest which logs a lot of harmless
errors.

Fixes: #6957

Co-authored-by: rahul2393 <irahul@google.com>

spanner/client.go

@@ -143,9 +143,9 @@ type ClientConfig struct {
 	// Recommended format: ``application-or-tool-ID/major.minor.version``.
 	UserAgent string
 
-	// logger is the logger to use for this client. If it is nil, all logging
+	// Logger is the logger to use for this client. If it is nil, all logging
 	// will be directed to the standard logger.
-	logger *log.Logger
+	Logger *log.Logger
 }
 
 func contextWithOutgoingMetadata(ctx context.Context, md metadata.MD) context.Context {
@@ -220,7 +220,7 @@ func NewClientWithConfig(ctx context.Context, database string, config ClientConf
 		config.incStep = DefaultSessionPoolConfig.incStep
 	}
 	// Create a session client.
-	sc := newSessionClient(pool, database, config.UserAgent, sessionLabels, metadata.Pairs(resourcePrefixHeader, database), config.logger, config.CallOptions)
+	sc := newSessionClient(pool, database, config.UserAgent, sessionLabels, metadata.Pairs(resourcePrefixHeader, database), config.Logger, config.CallOptions)
 	// Create a session pool.
 	config.SessionPoolConfig.sessionLabels = sessionLabels
 	sp, err := newSessionPool(sc, config.SessionPoolConfig)
@@ -231,7 +231,7 @@ func NewClientWithConfig(ctx context.Context, database string, config ClientConf
 	c = &Client{
 		sc:           sc,
 		idleSessions: sp,
-		logger:       config.logger,
+		logger:       config.Logger,
 		qo:           getQueryOptions(config.QueryOptions),
 		ro:           config.ReadOptions,
 		ao:           config.ApplyOptions,

spanner/pdml_test.go

@@ -114,7 +114,7 @@ func TestPartitionedUpdate_WithDeadline(t *testing.T) {
 	logger := log.New(os.Stderr, "", log.LstdFlags)
 	server, client, teardown := setupMockedTestServerWithConfig(t, ClientConfig{
 		SessionPoolConfig: DefaultSessionPoolConfig,
-		logger:            logger,
+		Logger:            logger,
 	})
 	defer teardown()
 

spanner/session_test.go

@@ -1122,7 +1122,7 @@ func TestErrorOnPrepareSession(t *testing.T) {
 					WriteSessions:       0.5,
 					HealthCheckInterval: time.Millisecond,
 				},
-				logger: logger,
+				Logger: logger,
 			})
 		defer teardown()
 		// Discard logging until trying to prepare sessions has stopped.
@@ -1244,7 +1244,7 @@ func TestSessionNotFoundOnPrepareSession(t *testing.T) {
 				HealthCheckInterval:       time.Millisecond,
 				healthCheckSampleInterval: time.Millisecond,
 			},
-			logger: logger,
+			Logger: logger,
 		})
 	defer teardown()
 	// Discard logging until trying to prepare sessions has stopped.