Only lookup local post when quering with "wp_jp_foreign_id" (#24586)

* Add an unit test to reproduce the linear issue JETPACK-537

The user's site have multiple posts with the same "wp_jp_foreign_id".

https://linear.app/a8c/issue/JETPACK-537

* Only lookup local post when quering with "wp_jp_foreign_id"

Author: crazytonyli

Sources/WordPressData/Objective-C/PostHelper.m

@@ -182,7 +182,7 @@ + (NSArray *)mergePosts:(NSArray <RemotePost *> *)remotePosts
         if (post == nil) {
             NSUUID *foreignID = remotePost.foreignID;
             if (foreignID != nil) {
-                post = [blog lookupPostWithForeignID:foreignID inContext:context];
+                post = [blog lookupLocalPostWithForeignID:foreignID inContext:context];
             }
         }
         if (!post) {

Sources/WordPressData/Swift/Blog+Post.swift

@@ -35,10 +35,10 @@ extension Blog {
     ///
     /// - Parameter foreignID: The foreign ID associated with the post; used to deduplicate new posts.
     /// - Returns: The `AbstractPost` associated with the given foreign ID.
-    @objc(lookupPostWithForeignID:inContext:)
-    public func lookupPost(withForeignID foreignID: UUID, in context: NSManagedObjectContext) -> AbstractPost? {
+    @objc(lookupLocalPostWithForeignID:inContext:)
+    public func lookupLocalPost(withForeignID foreignID: UUID, in context: NSManagedObjectContext) -> AbstractPost? {
         let request = NSFetchRequest<AbstractPost>(entityName: NSStringFromClass(AbstractPost.self))
-        request.predicate = NSPredicate(format: "blog = %@ AND original = NULL AND \(#keyPath(AbstractPost.foreignID)) == %@", self, foreignID as NSUUID)
+        request.predicate = NSPredicate(format: "blog = %@ AND original = NULL AND (postID = NULL OR postID <= 0) AND \(#keyPath(AbstractPost.foreignID)) == %@", self, foreignID as NSUUID)
         request.fetchLimit = 1
         return (try? context.fetch(request))?.first
     }

Tests/KeystoneTests/Tests/Services/PostRepositoryTests.swift

@@ -217,6 +217,30 @@ class PostRepositoryTests: CoreDataTestCase {
         }
     }
 
+    func testFetchPostsWithTheSameForeignID() async throws {
+        let posts = try (1...10).map {
+            let post = try XCTUnwrap(RemotePost(siteID: 1, status: "publish", title: "Post: Test", content: "This is a test post"))
+            post.postID = NSNumber(value: $0)
+            post.type = "post"
+
+            // Assign the same foreign id to a few posts
+            if $0 <= 3 {
+                post.metadata = [[
+                    "id": 1234,
+                    "key": PostHelper.foreignIDKey,
+                    "value": "892D484C-9972-47DE-8103-03A7FDE4EFCC"
+                ]]
+            }
+
+            return post
+        }
+
+        remoteMock.remotePostsToReturnOnSyncPostsOfType = [posts]
+
+        let _ = try await repository.paginate(type: Post.self, statuses: [.publish], offset: 0, number: 100, in: blogID)
+        let numberOfPosts = try await contextManager.performQuery { $0.countObjects(ofType: Post.self) }
+        XCTAssertEqual(numberOfPosts, 10)
+    }
 }
 
 // These mock classes are copied from PostServiceWPComTests. We can't simply remove the `private` in the original class