Merge pull request #708 from khlopko/issue-693

#693: DataPublisher created from async function should start lazily
kean · Jun 23, 2023 · a84b6ce · a84b6ce
2 parents bf95178 + 0655d2b
commit a84b6ce
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Showing 3 changed files with 53 additions and 10 deletions.
diff --git a/Nuke.xcodeproj/project.pbxproj b/Nuke.xcodeproj/project.pbxproj
@@ -266,6 +266,7 @@
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 		0CF58FF726DAAC3800D2650D /* ImageDownsampleTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0CF58FF626DAAC3800D2650D /* ImageDownsampleTests.swift */; };
 		2DFD93B0233A6AB300D84DB9 /* ImagePipelineProcessorTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2DFD93AF233A6AB300D84DB9 /* ImagePipelineProcessorTests.swift */; };
+		4480674C2A448C9F00DE7CF8 /* DataPublisherTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4480674B2A448C9F00DE7CF8 /* DataPublisherTests.swift */; };
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@@ -537,6 +538,7 @@
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 		0CF58FF626DAAC3800D2650D /* ImageDownsampleTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ImageDownsampleTests.swift; sourceTree = "<group>"; };
 		2DFD93AF233A6AB300D84DB9 /* ImagePipelineProcessorTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ImagePipelineProcessorTests.swift; sourceTree = "<group>"; };
+		4480674B2A448C9F00DE7CF8 /* DataPublisherTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DataPublisherTests.swift; sourceTree = "<group>"; };
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@@ -709,6 +711,7 @@
 			isa = PBXGroup;
 			children = (
 				0C1E620A1D6F817700AD5CF5 /* ImageRequestTests.swift */,
+				4480674B2A448C9F00DE7CF8 /* DataPublisherTests.swift */,
 				0C7C06871BCA888800089D7F /* ImageCacheTests.swift */,
 				0C70D9772089017500A49DAC /* ImageDecoderTests.swift */,
 				0C68F608208A1F40007DC696 /* ImageDecoderRegistryTests.swift */,
@@ -1617,6 +1620,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				4480674C2A448C9F00DE7CF8 /* DataPublisherTests.swift in Sources */,
 				0CD37C9A25BA36D5006C2C36 /* ImagePipelineLoadDataTests.swift in Sources */,
 				0C75279F1D473AEF00EC6222 /* MockImageProcessor.swift in Sources */,
 				0C69FA4E1D4E222D00DA9982 /* ImagePrefetcherTests.swift in Sources */,

diff --git a/Sources/Nuke/Internal/DataPublisher.swift b/Sources/Nuke/Internal/DataPublisher.swift
@@ -34,17 +34,18 @@ final class DataPublisher {
 }
 
 private func publisher(from closure: @Sendable @escaping () async throws -> Data) -> AnyPublisher<Data, Error> {
-    let subject = PassthroughSubject<Data, Error>()
-    Task {
-        do {
-            let data = try await closure()
-            subject.send(data)
-            subject.send(completion: .finished)
-        } catch {
-            subject.send(completion: .failure(error))
+    Deferred {
+        Future { promise in
+            Task {
+                do {
+                    let data = try await closure()
+                    promise(.success(data))
+                } catch {
+                    promise(.failure(error))
+                }
+            }
         }
-    }
-    return subject.eraseToAnyPublisher()
+    }.eraseToAnyPublisher()
 }
 
 enum PublisherCompletion {

diff --git a/Tests/NukeTests/DataPublisherTests.swift b/Tests/NukeTests/DataPublisherTests.swift
@@ -0,0 +1,38 @@
+//
+//  DataPublisherTests.swift
+//
+
+import XCTest
+import Combine
+@testable import Nuke
+
+internal final class DataPublisherTests: XCTestCase {
+
+    private var cancellable: (any Nuke.Cancellable)?
+
+    func testInitNotStartsExecutionRightAway() {
+        let operation = MockOperation()
+        let publisher = DataPublisher(id: UUID().uuidString, { await operation.execute() })
+
+        XCTAssertEqual(0, operation.executeCalls)
+
+        let expOp = expectation(description: "Waits for MockOperation to complete execution")
+        cancellable = publisher.sink { completion in expOp.fulfill() } receiveValue: { _ in }
+        waitForExpectations(timeout: 0.1)
+
+        XCTAssertEqual(1, operation.executeCalls)
+    }
+
+    private final class MockOperation: @unchecked Sendable {
+
+        private(set) var executeCalls = 0
+
+        func execute() async -> Data {
+            executeCalls += 1
+            await Task.yield()
+            return Data()
+        }
+
+    }
+
+}