address changes

Firestore/Source/Auth/FSTCredentialsProvider.h

@@ -29,7 +29,7 @@ NS_ASSUME_NONNULL_BEGIN
 /**
  * `FSTVoidTokenErrorBlock` is a block that gets a token or an error.
  *
- * @param token An auth token as a string.
+ * @param token An auth token, either valid or invalid when error occurred.
  * @param error The error if one occurred, or else `nil`.
  */
 typedef void (^FSTVoidGetTokenResultBlock)(const firebase::firestore::auth::Token &token,

Firestore/Source/Auth/FSTCredentialsProvider.mm

@@ -119,7 +119,7 @@ - (void)getTokenForcingRefresh:(BOOL)forceRefresh
             NSError *cancelError = [NSError errorWithDomain:FIRFirestoreErrorDomain
                                                        code:FIRFirestoreErrorCodeAborted
                                                    userInfo:errorInfo];
-            completion({"", User::Unauthenticated()}, cancelError);
+            completion(Token::Invalid(), cancelError);
           } else {
             Token result(util::MakeStringView(token), _currentUser);
             completion(result, error);

Firestore/Source/Auth/FSTEmptyCredentialsProvider.mm

@@ -19,8 +19,10 @@
 #import "Firestore/Source/Util/FSTAssert.h"
 #import "Firestore/Source/Util/FSTDispatchQueue.h"
 
+#include "Firestore/core/src/firebase/firestore/auth/token.h"
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
 
+using firebase::firestore::auth::Token;
 using firebase::firestore::auth::User;
 
 NS_ASSUME_NONNULL_BEGIN
@@ -29,7 +31,8 @@ @implementation FSTEmptyCredentialsProvider
 
 - (void)getTokenForcingRefresh:(BOOL)forceRefresh
                     completion:(FSTVoidGetTokenResultBlock)completion {
-  completion({"", User::Unauthenticated()}, nil);
+  // Invalid token will force the GRPC fallback to use default settings.
+  completion(Token::Invalid(), nil);
 }
 
 - (void)setUserChangeListener:(nullable FSTVoidUserBlock)block {

Firestore/Source/Remote/FSTDatastore.mm

@@ -301,22 +301,24 @@ - (void)invokeRPCWithFactory:(GRPCProtoCall * (^)(void))rpcFactory
                 errorHandler:(FSTVoidErrorBlock)errorHandler {
   // 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
-  [self.credentials getTokenForcingRefresh:NO
-                                completion:^(const Token &result, NSError *_Nullable error) {
-                                  error = [FSTDatastore firestoreErrorForError:error];
-                                  [self.workerDispatchQueue dispatchAsyncAllowingSameQueue:^{
-                                    if (error) {
-                                      errorHandler(error);
-                                    } else {
-                                      GRPCProtoCall *rpc = rpcFactory();
-                                      [FSTDatastore
-                                          prepareHeadersForRPC:rpc
-                                                    databaseID:&self.databaseInfo->database_id()
-                                                         token:result.token()];
-                                      [rpc start];
-                                    }
-                                  }];
-                                }];
+  [self.credentials
+      getTokenForcingRefresh:NO
+                  completion:^(const Token &result, NSError *_Nullable error) {
+                    error = [FSTDatastore firestoreErrorForError:error];
+                    [self.workerDispatchQueue dispatchAsyncAllowingSameQueue:^{
+                      if (error) {
+                        errorHandler(error);
+                      } else {
+                        GRPCProtoCall *rpc = rpcFactory();
+                        [FSTDatastore
+                            prepareHeadersForRPC:rpc
+                                      databaseID:&self.databaseInfo->database_id()
+                                           token:(result.is_valid() ? result.token()
+                                                                    : absl::string_view())];
+                        [rpc start];
+                      }
+                    }];
+                  }];
 }
 
 - (FSTWatchStream *)createWatchStream {
@@ -338,9 +340,12 @@ + (void)prepareHeadersForRPC:(GRPCCall *)rpc
                   databaseID:(const DatabaseId *)databaseID
                        token:(const absl::string_view)token {
   rpc.oauth2AccessToken =
-      [[NSString alloc] initWithBytes:const_cast<void *>(static_cast<const void *>(token.data()))
-                               length:token.length()
-                             encoding:NSUTF8StringEncoding];
+      token.data() == nullptr
+          ? nil
+          : [[NSString alloc]
+                initWithBytes:const_cast<void *>(static_cast<const void *>(token.data()))
+                       length:token.length()
+                     encoding:NSUTF8StringEncoding];
   rpc.requestHeaders[kXGoogAPIClientHeader] = [FSTDatastore googAPIClientHeaderValue];
   // This header is used to improve routing and project isolation by the backend.
   rpc.requestHeaders[kGoogleCloudResourcePrefix] =

Firestore/Source/Remote/FSTStream.mm

@@ -285,7 +285,7 @@ - (void)resumeStartWithToken:(const Token &)token error:(NSError *)error {
   _rpc = [self createRPCWithRequestsWriter:self.requestsWriter];
   [FSTDatastore prepareHeadersForRPC:_rpc
                           databaseID:&self.databaseInfo->database_id()
-                               token:token.token()];
+                               token:(token.is_valid() ? token.token() : absl::string_view())];
   FSTAssert(_callbackFilter == nil, @"GRX Filter must be nil");
   _callbackFilter = [[FSTCallbackFilter alloc] initWithStream:self];
   [_rpc startWithWriteable:_callbackFilter];

Firestore/core/src/firebase/firestore/auth/token.cc

@@ -21,7 +21,15 @@ namespace firestore {
 namespace auth {
 
 Token::Token(const absl::string_view token, const User& user)
-    : token_(token), user_(user) {
+    : token_(token), user_(user), is_valid_(true) {
+}
+
+Token::Token() : token_(), user_(User::Unauthenticated()), is_valid_(false) {
+}
+
+const Token& Token::Invalid() {
+  static const Token kInvalidToken;
+  return kInvalidToken;
 }
 
 }  // namespace auth

Firestore/core/src/firebase/firestore/auth/token.h

@@ -20,6 +20,7 @@
 #include <string>
 
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
+#include "Firestore/core/src/firebase/firestore/util/firebase_assert.h"
 #include "absl/strings/string_view.h"
 
 namespace firebase {
@@ -45,6 +46,7 @@ class Token {
 
   /** The actual raw token. */
   const std::string& token() const {
+    FIREBASE_ASSERT(is_valid_);
     return token_;
   }
 
@@ -56,9 +58,19 @@ class Token {
     return user_;
   }
 
+  bool is_valid() const {
+    return is_valid_;
+  }
+
+  /** Returns an invalid token. */
+  static const Token& Invalid();
+
  private:
+  Token();
+
   const std::string token_;
   const User user_;
+  const bool is_valid_;
 };
 
 }  // namespace auth

Firestore/core/test/firebase/firestore/auth/token_test.cc

@@ -26,6 +26,14 @@ TEST(Token, Getter) {
   Token token("token", User("abc"));
   EXPECT_EQ("token", token.token());
   EXPECT_EQ(User("abc"), token.user());
+  EXPECT_TRUE(token.is_valid());
+}
+
+TEST(Token, InvalidToken) {
+  const Token& token = Token::Invalid();
+  EXPECT_ANY_THROW(token.token());
+  EXPECT_EQ(User::Unauthenticated(), token.user());
+  EXPECT_FALSE(token.is_valid());
 }
 
 }  // namespace auth