Fix consumer is never called when extract uncompressed 0 byte entry

Sources/ZIPFoundation/Data+Serialization.swift

@@ -44,9 +44,14 @@ extension Data {
 
     static func consumePart(of size: Int, chunkSize: Int, skipCRC32: Bool = false,
                             provider: Provider, consumer: Consumer) throws -> CRC32 {
+        var checksum = CRC32(0)
+        guard size > 0 else {
+            try consumer(Data())
+            return checksum
+        }
+
         let readInOneChunk = (size < chunkSize)
         var chunkSize = readInOneChunk ? size : chunkSize
-        var checksum = CRC32(0)
         var bytesRead = 0
         while bytesRead < size {
             let remainingSize = size - bytesRead

Tests/ZIPFoundationTests/ZIPFoundationReadingTests.swift

@@ -227,6 +227,24 @@ extension ZIPFoundationTests {
         XCTAssert(entriesRead == 0)
     }
 
+    func testExtractUncompressedEmptyFile() {
+        // We had a logic error, where completion handlers for empty entries were not called
+        // Ensure that this edge case works
+        var didCallCompletion = false
+        let archive = self.archive(for: #function, mode: .read)
+        guard let entry = archive["empty.txt"] else { XCTFail("Failed to extract entry."); return }
+
+        do {
+            _ = try archive.extract(entry) { (data) in
+                XCTAssertEqual(data.count, 0)
+                didCallCompletion = true
+            }
+        } catch {
+            XCTFail("Unexpected error while trying to extract empty file of uncompressed archive.")
+        }
+        XCTAssert(didCallCompletion)
+    }
+
     func testExtractUncompressedEntryCancelation() {
         let archive = self.archive(for: #function, mode: .read)
         guard let entry = archive["original"] else { XCTFail("Failed to extract entry."); return }

Tests/ZIPFoundationTests/ZIPFoundationTests.swift

@@ -286,6 +286,7 @@ extension ZIPFoundationTests {
             ("testExtractMSDOSArchive", testExtractMSDOSArchive),
             ("testExtractUncompressedDataDescriptorArchive", testExtractUncompressedDataDescriptorArchive),
             ("testExtractUncompressedFolderEntries", testExtractUncompressedFolderEntries),
+            ("testExtractUncompressedEmptyFile", testExtractUncompressedEmptyFile),
             ("testExtractZIP64ArchiveErrorConditions", testExtractZIP64ArchiveErrorConditions),
             ("testFileAttributeHelperMethods", testFileAttributeHelperMethods),
             ("testFilePermissionHelperMethods", testFilePermissionHelperMethods),