Post / Page creation: Don't send default Post.authorID to the API

RELEASE-NOTES.txt

@@ -1,5 +1,6 @@
 21.4
 -----
+* [*] Fixed an issue where publishing Posts and Pages could fail under certain conditions. [#19717]
 * [*] Share extension navigation bar is no longer transparent [#19700]
 
 21.3

WordPress/Classes/Services/PostService.h

@@ -160,6 +160,13 @@ forceDraftIfCreating:(BOOL)forceDraftIfCreating
            success:(nullable void (^)(void))success
            failure:(void (^)(NSError * _Nullable error))failure;
 
+/**
+ Creates a RemotePost from an AbstractPost to be used for API calls.
+
+ @param post The AbstractPost used to create the RemotePost
+ */
+- (RemotePost *)remotePostWithPost:(AbstractPost *)post;
+
 @end
 
 NS_ASSUME_NONNULL_END

WordPress/Classes/Services/PostService.m

@@ -814,7 +814,11 @@ - (RemotePost *)remotePostWithPost:(AbstractPost *)post
     remotePost.password = post.password;
     remotePost.type = @"post";
     remotePost.authorAvatarURL = post.authorAvatarURL;
-    remotePost.authorID = post.authorID;
+    // If a Post's authorID is 0 (the default Core Data value)
+    // or nil, don't send it to the API.
+    if (post.authorID.integerValue != 0) {
+        remotePost.authorID = post.authorID;
+    }
     remotePost.excerpt = post.mt_excerpt;
     remotePost.slug = post.wp_slug;
 

WordPress/WordPressTest/Services/PostServiceWPComTests.swift

@@ -293,6 +293,49 @@ class PostServiceWPComTests: CoreDataTestCase {
         wait(for: [expectation], timeout: timeout)
     }
 
+    /// The default `Post.authorID` value (currently 0 in the Core Data model) should
+    /// be `nil` for `RemotePost`s.
+    func testRemotePostAuthorIDNilForDefaultPostAuthorID() {
+        // Given
+        let post = PostBuilder(mainContext).build()
+        try! mainContext.save()
+
+        // When
+        let remotePost = self.service.remotePost(with: post)
+
+        // Then
+        XCTAssertNil(remotePost.authorID)
+    }
+
+    /// `Post.authorID`s set to `nil` should be `nil` for `RemotePost`s.
+    func testRemotePostAuthorIDNilForNilPostAuthorID() {
+        // Given
+        let post = PostBuilder(mainContext).build()
+        post.authorID = nil
+        try! mainContext.save()
+
+        // When
+        let remotePost = self.service.remotePost(with: post)
+
+        // Then
+        XCTAssertNil(remotePost.authorID)
+    }
+
+    /// `Post.authorID`s set to a valid value should be reflected in `RemotePost`s.
+    func testRemotePostAuthorSetForValidPostAuthorID() {
+        // Given
+        let expectedAuthorID: NSNumber = 1
+        let post = PostBuilder(mainContext).build()
+        post.authorID = expectedAuthorID
+        try! mainContext.save()
+
+        // When
+        let remotePost = self.service.remotePost(with: post)
+
+        // Then
+        XCTAssertEqual(remotePost.authorID, expectedAuthorID)
+    }
+
     private func createRemotePost(_ status: BasePost.Status = .draft) -> RemotePost {
         let remotePost = RemotePost(siteID: 1,
                                     status: status.rawValue,