Change CredentialsProvider::TokenListener to use StatusOr<Token> (#945)

* Change CredentialsProvider::TokenListener to use StatusOr

Rather than a token plus error code/msg.

* Eliminate the concept of an invalid Token

Instead, we'll just use StatusOr<Token>. Note that unauthenticated
tokens are handled as a special case; they're created via:
  Token::Unauthenticated()
and are otherwise "valid", though attempting to retrieve the raw token
on one of these tokens will cause an assertion failure.

2 files changed, 12 insertions, 15 deletions

diff --git a/Firestore/Source/Remote/FSTDatastore.mm b/Firestore/Source/Remote/FSTDatastore.mm
index e63017a..63499df 100644
--- a/Firestore/Source/Remote/FSTDatastore.mm
+++ b/Firestore/Source/Remote/FSTDatastore.mm
@@ -305,20 +305,18 @@ typedef GRPCProtoCall * (^RPCFactory)(void);
   // TODO(mikelehen): We should force a refresh if the previous RPC failed due to an expired token,
   // but I'm not sure how to detect that right now. http://b/32762461
   _credentials->GetToken(
-      /*force_refresh=*/false,
-      [self, rpcFactory, errorHandler](Token result, const int64_t error_code,
-                                       const absl::string_view error_msg) {
-        NSError *error = util::WrapNSError(error_code, error_msg);
+      /*force_refresh=*/false, [self, rpcFactory, errorHandler](util::StatusOr<Token> result) {
         [self.workerDispatchQueue dispatchAsyncAllowingSameQueue:^{
-          if (error) {
-            errorHandler(error);
+          if (!result.ok()) {
+            errorHandler(util::MakeNSError(result.status()));
           } else {
             GRPCProtoCall *rpc = rpcFactory();
+            const Token &token = result.ValueOrDie();
             [FSTDatastore
                 prepareHeadersForRPC:rpc
                           databaseID:&self.databaseInfo->database_id()
-                               token:(result.user().is_authenticated() ? result.token()
-                                                                       : absl::string_view())];
+                               token:(token.user().is_authenticated() ? token.token()
+                                                                      : absl::string_view())];
             [rpc start];
           }
         }];
diff --git a/Firestore/Source/Remote/FSTStream.mm b/Firestore/Source/Remote/FSTStream.mm
index 019b0bc..a5c36c8 100644
--- a/Firestore/Source/Remote/FSTStream.mm
+++ b/Firestore/Source/Remote/FSTStream.mm
@@ -265,17 +265,15 @@ static const NSTimeInterval kIdleTimeout = 60.0;
   _delegate = delegate;
 
   _credentials->GetToken(
-      /*force_refresh=*/false,
-      [self](Token result, const int64_t error_code, const absl::string_view error_msg) {
-        NSError *error = util::WrapNSError(error_code, error_msg);
+      /*force_refresh=*/false, [self](util::StatusOr<Token> result) {
         [self.workerDispatchQueue dispatchAsyncAllowingSameQueue:^{
-          [self resumeStartWithToken:result error:error];
+          [self resumeStartWithToken:result];
         }];
       });
 }
 
 /** Add an access token to our RPC, after obtaining one from the credentials provider. */
-- (void)resumeStartWithToken:(const Token &)token error:(NSError *)error {
+- (void)resumeStartWithToken:(const util::StatusOr<Token> &)result {
   [self.workerDispatchQueue verifyIsCurrentQueue];
 
   if (self.state == FSTStreamStateStopped) {
@@ -287,9 +285,9 @@ static const NSTimeInterval kIdleTimeout = 60.0;
 
   // TODO(mikelehen): We should force a refresh if the previous RPC failed due to an expired token,
   // but I'm not sure how to detect that right now. http://b/32762461
-  if (error) {
+  if (!result.ok()) {
     // RPC has not been started yet, so just invoke higher-level close handler.
-    [self handleStreamClose:error];
+    [self handleStreamClose:util::MakeNSError(result.status())];
     return;
   }
 
@@ -297,6 +295,7 @@ static const NSTimeInterval kIdleTimeout = 60.0;
   _rpc = [self createRPCWithRequestsWriter:self.requestsWriter];
   [_rpc setResponseDispatchQueue:self.workerDispatchQueue.queue];
 
+  const Token &token = result.ValueOrDie();
   [FSTDatastore
       prepareHeadersForRPC:_rpc
                 databaseID:&self.databaseInfo->database_id()