Merge pull request #5679 from wikimedia/dedupe-summary-requests

Activity tab - Dedupe in-flight summary requests

Author: tonisevener

WMFData/Sources/WMFData/Data Controllers/Saved Articles/WMFSavedArticlesDataController.swift

@@ -14,7 +14,7 @@ public actor WMFSavedArticlesDataController {
     // MARK: - Lifecycle
 
     public init(coreDataStore: WMFCoreDataStore? = WMFDataEnvironment.current.coreDataStore,
-                articleSummaryDataController: WMFArticleSummaryDataController = .init()
+                articleSummaryDataController: WMFArticleSummaryDataController = WMFArticleSummaryDataController.shared
     ) {
         self._coreDataStore = coreDataStore
         self.articleSummaryDataController = articleSummaryDataController

WMFData/Sources/WMFData/Data Controllers/Shared/WMFArticleSummaryDataController.swift

@@ -11,8 +11,9 @@ public actor WMFArticleSummaryDataController: WMFArticleSummaryDataControlling {
     public static var shared = WMFArticleSummaryDataController()
 
     private var cache: [WMFPage: WMFArticleSummary] = [:]
+    private var inFlightRequests: [WMFPage: [(Result<WMFArticleSummary, Error>) -> Void]] = [:]
 
-    public init() {
+    private init() {
         self.service = WMFDataEnvironment.current.basicService
     }
 
@@ -24,14 +25,26 @@ public actor WMFArticleSummaryDataController: WMFArticleSummaryDataControlling {
             return
         }
 
+        // Check if there's already an in-flight request for this page
+        if inFlightRequests[wmfPage] != nil {
+            // Queue this completion to be called when the in-flight request completes
+            inFlightRequests[wmfPage]?.append(completion)
+            return
+        }
+        
+        // Initialize the in-flight request tracking with the first completion
+        inFlightRequests[wmfPage] = [completion]
+        
         guard let service else {
-            completion(.failure(WMFDataControllerError.basicServiceUnavailable))
+            let error = WMFDataControllerError.basicServiceUnavailable
+            resolveInFlightRequests(for: wmfPage, with: .failure(error))
             return
         }
 
         guard !title.isEmpty,
               let url = URL.wikimediaRestAPIURL(project: project, additionalPathComponents: ["page", "summary", title.spacesToUnderscores]) else {
-            completion(.failure(WMFDataControllerError.failureCreatingRequestURL))
+            let error = WMFDataControllerError.failureCreatingRequestURL
+            resolveInFlightRequests(for: wmfPage, with: .failure(error))
             return
         }
 
@@ -43,20 +56,32 @@ public actor WMFArticleSummaryDataController: WMFArticleSummaryDataControlling {
                 Task { [weak self] in
                     guard let self else { return }
                     await self.updateCache(page: wmfPage, summary: summary)
+                    await self.resolveInFlightRequests(for: wmfPage, with: result)
                 }
 
-            default:
-                break
+            case .failure:
+                Task { [weak self] in
+                    guard let self else { return }
+                    await self.resolveInFlightRequests(for: wmfPage, with: result)
+                }
             }
-            
-            completion(result)
         }
     }
 
     private func updateCache(page: WMFPage, summary: WMFArticleSummary) {
         cache[page] = summary
     }
 
+    private func resolveInFlightRequests(for page: WMFPage, with result: Result<WMFArticleSummary, Error>) {
+        guard let completions = inFlightRequests[page] else { return }
+        inFlightRequests.removeValue(forKey: page)
+        
+        // Call all waiting completions with the result
+        for completion in completions {
+            completion(result)
+        }
+    }
+    
     public func fetchArticleSummary(project: WMFProject, title: String) async throws -> WMFArticleSummary {
         return try await withCheckedThrowingContinuation { continuation in
             fetchArticleSummary(project: project, title: title) { result in

WMFData/Tests/WMFDataTests/WMFGrowthTasksDataControllerTests.swift

@@ -89,7 +89,7 @@ final class WMFGrowthTasksDataControllerTests: XCTestCase {
 
     func testFetchArticleSummary() async throws {
 
-        let controller = WMFArticleSummaryDataController()
+        let controller = WMFArticleSummaryDataController.shared
 
         let articleSummaryToTest = try await controller.fetchArticleSummary(project: csProject, title: "Novela (právo)")