Infer Database URL from project ID (#6332)

Author: schmidt-sebastian

FirebaseDatabase/CHANGELOG.md

@@ -1,3 +1,7 @@
+# Unreleased
+- [feature] The SDK can now infer a default database URL if none is provided in
+  the config.
+
 # v6.4.0
 - [changed] Functionally neutral source reorganization. (#5861)
 

FirebaseDatabase/Sources/Api/FIRDatabase.m

@@ -67,7 +67,22 @@ + (FIRDatabase *)databaseForApp:(FIRApp *)app {
         [NSException raise:@"InvalidFIRApp"
                     format:@"nil FIRApp instance passed to databaseForApp."];
     }
-    return [FIRDatabase databaseForApp:app URL:app.options.databaseURL];
+    NSString *url = app.options.databaseURL;
+    if (!url) {
+        if (!app.options.projectID) {
+            [NSException
+                 raise:@"MissingProjectId"
+                format:@"Can't determine Firebase Database URL. Be sure to "
+                       @"include a Project ID when calling "
+                       @"`FirebaseApp.configure()`."];
+        }
+        FFLog(@"I-RDB024002", @"Using default host for project %@",
+              app.options.projectID);
+        url = [NSString
+            stringWithFormat:@"https://%@-default-rtdb.firebaseio.com",
+                             app.options.projectID];
+    }
+    return [FIRDatabase databaseForApp:app URL:url];
 }
 
 + (FIRDatabase *)databaseForApp:(FIRApp *)app URL:(NSString *)url {

FirebaseDatabase/Tests/Helpers/FIRFakeApp.h

@@ -21,7 +21,7 @@
 
 @interface FIRFakeApp : NSObject
 
-- (instancetype)initWithName:(NSString *)name URL:(NSString *)url;
+- (instancetype)initWithName:(NSString *)name URL:(NSString *_Nullable)url;
 
 @property(nonatomic, readonly) FIRFakeOptions *options;
 @property(nonatomic, copy, readonly) NSString *name;

FirebaseDatabase/Tests/Helpers/FIRFakeApp.m

@@ -21,17 +21,19 @@
 #import "SharedTestUtilities/FIRComponentTestUtilities.h"
 
 @interface FIRFakeOptions : NSObject
-@property(nonatomic, readonly, copy) NSString *databaseURL;
+@property(nonatomic, readonly, copy) NSString *_Nullable databaseURL;
+@property(nonatomic, readonly, copy) NSString *projectID;
 @property(nonatomic, readonly, copy) NSString *googleAppID;
-- (instancetype)initWithURL:(NSString *)url;
+- (instancetype)initWithURL:(NSString *_Nullable)url;
 @end
 
 @implementation FIRFakeOptions
-- (instancetype)initWithURL:(NSString *)url {
+- (instancetype)initWithURL:(NSString *_Nullable)url {
   self = [super init];
   if (self) {
     _databaseURL = url;
     _googleAppID = @"fake-app-id";
+    _projectID = @"fake-project-id";
   }
   return self;
 }
@@ -64,7 +66,7 @@ - (instancetype)initWithApp:(FIRApp *)app
 
 @implementation FIRFakeApp
 
-- (instancetype)initWithName:(NSString *)name URL:(NSString *)url {
+- (instancetype)initWithName:(NSString *)name URL:(NSString *_Nullable)url {
   self = [super init];
   if (self) {
     _name = name;

FirebaseDatabase/Tests/Integration/FIRDatabaseTests.m

@@ -49,7 +49,6 @@ - (void)testDatabaseForApp {
 }
 
 - (void)testDatabaseForAppWithInvalidURLs {
-  XCTAssertThrows([self databaseForURL:nil]);
   XCTAssertThrows([self databaseForURL:@"not-a-url"]);
   XCTAssertThrows([self databaseForURL:@"http://x.example.com/paths/are/bad"]);
 }
@@ -75,6 +74,13 @@ - (void)testDatabaseForAppWithHttpsURL {
   XCTAssertEqualObjects(@"https://foo.bar.com", [database reference].URL);
 }
 
+- (void)testDatabaseForAppWithProjectId {
+  id app = [[FIRFakeApp alloc] initWithName:@"testDatabaseForAppWithURL" URL:nil];
+  FIRDatabase *database = [FIRDatabase databaseForApp:app];
+  XCTAssertEqualObjects(@"https://fake-project-id-default-rtdb.firebaseio.com",
+                        [database reference].URL);
+}
+
 - (void)testDifferentInstanceForAppWithURL {
   id app = [[FIRFakeApp alloc] initWithName:@"testDifferentInstanceForAppWithURL"
                                         URL:kFirebaseTestAltNamespace];