Merge pull request #27 from cwakamo/fix-empty-views-and-images

[PlaygroundLogger] Better handle encoding of empty images and views.

Author: cwakamo

PlaygroundLogger/PlaygroundLogger/OpaqueRepresentations/AppKit/NSImage+OpaqueImageRepresentable.swift

@@ -34,7 +34,14 @@
 
         func encodeImage(into encoder: LogEncoder, withFormat format: LogEncoder.Format) throws {
             guard let bitmapRep = self.bestBitmapRepresentation else {
-                throw LoggingError.encodingFailure(reason: "Failed to get a bitmap representation of this NSImage")
+                if size == .zero {
+                    // If we couldn't get a bitmap representation because the image was empty, encode empty PNG data.
+                    encoder.encode(number: 0)
+                    return
+                }
+                else {
+                    throw LoggingError.encodingFailure(reason: "Failed to get a bitmap representation of this NSImage")
+                }
             }
 
             try bitmapRep.encodeImage(into: encoder, withFormat: format)

PlaygroundLogger/PlaygroundLogger/OpaqueRepresentations/AppKit/NSView+OpaqueImageRepresentable.swift

@@ -16,7 +16,14 @@
     extension NSView: OpaqueImageRepresentable {
         func encodeImage(into encoder: LogEncoder, withFormat format: LogEncoder.Format) throws {
             guard let bitmapRep = self.bitmapImageRepForCachingDisplay(in: self.bounds) else {
-                throw LoggingError.encodingFailure(reason: "Unable to create a bitmap representation of this NSView")
+                if self.bounds == .zero {
+                    // If we couldn't get a bitmap representation because the view is zero-sized, encode empty PNG data.
+                    encoder.encode(number: 0)
+                    return
+                }
+                else {
+                    throw LoggingError.encodingFailure(reason: "Unable to create a bitmap representation of this NSView")
+                }
             }
 
             self.cacheDisplay(in: self.bounds, to: bitmapRep)

PlaygroundLogger/PlaygroundLogger/OpaqueRepresentations/UIKit/UIImage+OpaqueImageRepresentable.swift

@@ -16,7 +16,15 @@
     extension UIImage: OpaqueImageRepresentable {
         func encodeImage(into encoder: LogEncoder, withFormat format: LogEncoder.Format) throws {
             guard let pngData = UIImagePNGRepresentation(self) else {
-                throw LoggingError.encodingFailure(reason: "Failed to convert UIImage to PNG")
+                if size == .zero {
+                    // We tried encoding an empty image, so it understandably failed.
+                    // In this case, simply encode empty PNG data.
+                    encoder.encode(number: 0)
+                    return
+                }
+                else {
+                    throw LoggingError.encodingFailure(reason: "Failed to convert UIImage to PNG")
+                }
             }
 
             encoder.encode(number: UInt64(pngData.count))

PlaygroundLogger/PlaygroundLoggerTests/LogEntryTests.swift

@@ -15,6 +15,12 @@ import XCTest
 
 import Foundation
 
+#if os(macOS)
+    import AppKit
+#elseif os(iOS) || os(tvOS)
+    import UIKit
+#endif
+
 class LogEntryTests: XCTestCase {
     func testNilIUO() throws {
         let nilIUO: Int! = nil
@@ -30,4 +36,48 @@ class LogEntryTests: XCTestCase {
         XCTAssertEqual(totalChildrenCount, 0)
         XCTAssert(children.isEmpty)
     }
+
+    func testEmptyView() throws {
+        #if os(macOS)
+            let emptyView = NSView()
+        #elseif os(iOS) || os(tvOS)
+            let emptyView = UIView()
+        #endif
+
+        let logEntry = try LogEntry(describing: emptyView, name: "emptyView", policy: .default)
+
+        guard case let .opaque(name, _, _, _, representation) = logEntry else {
+            XCTFail("Expected an opaque log entry")
+            return
+        }
+
+        XCTAssertEqual(name, "emptyView")
+        XCTAssert(representation is ImageOpaqueRepresentation)
+
+        // Try to encode the log entry. This operation shouldn't throw; if it does, it will fail the test.
+        let encoder = LogEncoder()
+        try logEntry.encode(with: encoder, format: .current)
+    }
+
+    func testEmptyImage() throws {
+        #if os(macOS)
+            let emptyImage = NSImage()
+        #elseif os(iOS) || os(tvOS)
+            let emptyImage = UIImage()
+        #endif
+
+        let logEntry = try LogEntry(describing: emptyImage, name: "emptyImage", policy: .default)
+
+        guard case let .opaque(name, _, _, _, representation) = logEntry else {
+            XCTFail("Expected an opaque log entry")
+            return
+        }
+
+        XCTAssertEqual(name, "emptyImage")
+        XCTAssert(representation is ImageOpaqueRepresentation)
+
+        // Try to encode the log entry. This operation shouldn't throw; if it does, it will fail the test.
+        let encoder = LogEncoder()
+        try logEntry.encode(with: encoder, format: .current)
+    }
 }