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.

5 files changed, 51 insertions, 50 deletions

diff --git a/Firestore/core/src/firebase/firestore/auth/credentials_provider.h b/Firestore/core/src/firebase/firestore/auth/credentials_provider.h
index b9a8a24..1aa76df 100644
--- a/Firestore/core/src/firebase/firestore/auth/credentials_provider.h
+++ b/Firestore/core/src/firebase/firestore/auth/credentials_provider.h
@@ -23,6 +23,7 @@
 #include "Firestore/core/include/firebase/firestore/firestore_errors.h"
 #include "Firestore/core/src/firebase/firestore/auth/token.h"
 #include "Firestore/core/src/firebase/firestore/auth/user.h"
+#include "Firestore/core/src/firebase/firestore/util/statusor.h"
 #include "absl/strings/string_view.h"
 
 namespace firebase {
@@ -30,12 +31,7 @@ namespace firestore {
 namespace auth {
 
 // `TokenErrorListener` is a listener that gets a token or an error.
-// token: An auth token as a string, or nullptr if error occurred.
-// error_code: The error code if one occurred, or else FirestoreErrorCode::Ok.
-// error_msg: The error if one occurred, or else nullptr.
-typedef std::function<void(
-    Token token, const int64_t error_code, const absl::string_view error_msg)>
-    TokenListener;
+typedef std::function<void(util::StatusOr<Token>)> TokenListener;
 
 // Listener notified with a User change.
 typedef std::function<void(User user)> UserChangeListener;
diff --git a/Firestore/core/src/firebase/firestore/auth/empty_credentials_provider.cc b/Firestore/core/src/firebase/firestore/auth/empty_credentials_provider.cc
index 0fa70c0..da4198d 100644
--- a/Firestore/core/src/firebase/firestore/auth/empty_credentials_provider.cc
+++ b/Firestore/core/src/firebase/firestore/auth/empty_credentials_provider.cc
@@ -26,8 +26,9 @@ void EmptyCredentialsProvider::GetToken(bool force_refresh,
                                         TokenListener completion) {
   UNUSED(force_refresh);
   if (completion) {
-    // Invalid token will force the GRPC fallback to use default settings.
-    completion(Token::Invalid(), FirestoreErrorCode::Ok, "");
+    // Unauthenticated token will force the GRPC fallback to use default
+    // settings.
+    completion(Token::Unauthenticated());
   }
 }
 
diff --git a/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.mm b/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.mm
index 1babe82..2bd3acc 100644
--- a/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.mm
+++ b/Firestore/core/src/firebase/firestore/auth/firebase_credentials_provider_apple.mm
@@ -23,6 +23,9 @@
 #include "Firestore/core/src/firebase/firestore/util/firebase_assert.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
+// NB: This is also defined in Firestore/Source/Public/FIRFirestoreErrors.h
+NSString* const FIRFirestoreErrorDomain = @"FIRFirestoreErrorDomain";
+
 namespace firebase {
 namespace firestore {
 namespace auth {
@@ -84,27 +87,38 @@ void FirebaseCredentialsProvider::GetToken(bool force_refresh,
   int initial_user_counter = contents_->user_counter;
 
   std::weak_ptr<Contents> weak_contents = contents_;
-  void (^get_token_callback)(NSString*, NSError*) = ^(
-      NSString* _Nullable token, NSError* _Nullable error) {
-    std::shared_ptr<Contents> contents = weak_contents.lock();
-    if (!contents) {
-      return;
-    }
-
-    std::unique_lock<std::mutex> lock(contents->mutex);
-    if (initial_user_counter != contents->user_counter) {
-      // Cancel the request since the user changed while the request was
-      // outstanding so the response is likely for a previous user (which
-      // user, we can't be sure).
-      completion(Token::Invalid(), FirestoreErrorCode::Aborted,
-                 "getToken aborted due to user change.");
-    } else {
-      completion(
-          Token{util::MakeStringView(token), contents->current_user},
-          error == nil ? FirestoreErrorCode::Ok : error.code,
-          error == nil ? "" : util::MakeStringView(error.localizedDescription));
-    }
-  };
+  void (^get_token_callback)(NSString*, NSError*) =
+      ^(NSString* _Nullable token, NSError* _Nullable error) {
+        std::shared_ptr<Contents> contents = weak_contents.lock();
+        if (!contents) {
+          return;
+        }
+
+        std::unique_lock<std::mutex> lock(contents->mutex);
+        if (initial_user_counter != contents->user_counter) {
+          // Cancel the request since the user changed while the request was
+          // outstanding so the response is likely for a previous user (which
+          // user, we can't be sure).
+          completion(util::Status(FirestoreErrorCode::Aborted,
+                                  "getToken aborted due to user change."));
+        } else {
+          if (error == nil) {
+            if (token != nil) {
+              completion(
+                  Token{util::MakeStringView(token), contents->current_user});
+            } else {
+              completion(Token::Unauthenticated());
+            }
+          } else {
+            FirestoreErrorCode error_code = FirestoreErrorCode::Unknown;
+            if (error.domain == FIRFirestoreErrorDomain) {
+              error_code = static_cast<FirestoreErrorCode>(error.code);
+            }
+            completion(util::Status(
+                error_code, util::MakeStringView(error.localizedDescription)));
+          }
+        }
+      };
 
   [contents_->app getTokenForcingRefresh:force_refresh
                             withCallback:get_token_callback];
diff --git a/Firestore/core/src/firebase/firestore/auth/token.cc b/Firestore/core/src/firebase/firestore/auth/token.cc
index 4ee1b69..6fe5fc4 100644
--- a/Firestore/core/src/firebase/firestore/auth/token.cc
+++ b/Firestore/core/src/firebase/firestore/auth/token.cc
@@ -21,15 +21,13 @@ namespace firestore {
 namespace auth {
 
 Token::Token(const absl::string_view token, const User& user)
-    : token_(token), user_(user), is_valid_(true) {
+    : token_(token), user_(user) {
 }
 
-Token::Token() : token_(), user_(User::Unauthenticated()), is_valid_(false) {
-}
-
-const Token& Token::Invalid() {
-  static const Token kInvalidToken;
-  return kInvalidToken;
+const Token& Token::Unauthenticated() {
+  static const Token kUnauthenticatedToken(absl::string_view(),
+                                           User::Unauthenticated());
+  return kUnauthenticatedToken;
 }
 
 }  // namespace auth
diff --git a/Firestore/core/src/firebase/firestore/auth/token.h b/Firestore/core/src/firebase/firestore/auth/token.h
index ff8d2f0..4b2f3aa 100644
--- a/Firestore/core/src/firebase/firestore/auth/token.h
+++ b/Firestore/core/src/firebase/firestore/auth/token.h
@@ -46,7 +46,7 @@ class Token {
 
   /** The actual raw token. */
   const std::string& token() const {
-    FIREBASE_ASSERT(is_valid_);
+    FIREBASE_ASSERT(user_.is_authenticated());
     return token_;
   }
 
@@ -59,25 +59,17 @@ class Token {
   }
 
   /**
-   * Whether the token is a valid one.
+   * Returns a token for an unauthenticated user.
    *
-   * ## Portability notes: Invalid token is the equivalent of nil in the iOS
-   * token implementation. We use value instead of pointer for Token instance in
-   * the C++ migration.
+   * ## Portability notes: An unauthenticated token is the equivalent of
+   * nil/null in the iOS/TypeScript token implementation. We use a reference
+   * instead of a pointer for Token instances in the C++ migration.
    */
-  bool is_valid() const {
-    return is_valid_;
-  }
-
-  /** Returns an invalid token. */
-  static const Token& Invalid();
+  static const Token& Unauthenticated();
 
  private:
-  Token();
-
   const std::string token_;
   const User user_;
-  const bool is_valid_;
 };
 
 }  // namespace auth