[webview_flutter_wkwebview] Change callback methods with a non-null return type to non-null (flutter#8564)

Callback methods that can't return nullable value are made non-null. If the error seen by issues listed below, this should make the failure happen in Dart.

Related:
flutter#162437
flutter#162368

Fixes flutter#125901

Author: bparrishMines

packages/webview_flutter/webview_flutter_wkwebview/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 3.18.1
+
+* Fixes bug that would allow the API wrapper to return `null` when a non-null value was required in
+  a callback method.
+* Changes default method to enable JavaScript for web content to
+  `WKWebpagePreferences.allowsContentJavaScript`. 
+
 ## 3.18.0
 
 * Updates internal API wrapper to use ProxyApis.

packages/webview_flutter/webview_flutter_wkwebview/darwin/Tests/PreferencesProxyAPITests.swift

@@ -8,15 +8,20 @@ import XCTest
 @testable import webview_flutter_wkwebview
 
 class PreferencesProxyAPITests: XCTestCase {
-  @MainActor func testSetJavaScriptEnabled() {
-    let registrar = TestProxyApiRegistrar()
-    let api = registrar.apiDelegate.pigeonApiWKPreferences(registrar)
+  @MainActor func testSetJavaScriptEnabled() throws {
+    if #available(iOS 14.0, macOS 11.0, *) {
+      throw XCTSkip("Required API is not available for this test.")
 
-    let instance = WKPreferences()
-    let enabled = true
-    try? api.pigeonDelegate.setJavaScriptEnabled(
-      pigeonApi: api, pigeonInstance: instance, enabled: enabled)
+    } else {
+      let registrar = TestProxyApiRegistrar()
+      let api = registrar.apiDelegate.pigeonApiWKPreferences(registrar)
 
-    XCTAssertEqual(instance.javaScriptEnabled, enabled)
+      let instance = WKPreferences()
+      let enabled = true
+      try? api.pigeonDelegate.setJavaScriptEnabled(
+        pigeonApi: api, pigeonInstance: instance, enabled: enabled)
+
+      XCTAssertEqual(instance.javaScriptEnabled, enabled)
+    }
   }
 }

packages/webview_flutter/webview_flutter_wkwebview/darwin/Tests/WebViewConfigurationProxyAPITests.swift

@@ -123,4 +123,16 @@ class WebViewConfigurationProxyAPITests: XCTestCase {
 
     XCTAssertEqual(instance.mediaTypesRequiringUserActionForPlayback, [])
   }
+
+  @available(iOS 13.0, macOS 10.15, *)
+  @MainActor func testGetDefaultWebpagePreferences() {
+    let registrar = TestProxyApiRegistrar()
+    let api = registrar.apiDelegate.pigeonApiWKWebViewConfiguration(registrar)
+
+    let instance = WKWebViewConfiguration()
+    let value = try? api.pigeonDelegate.getDefaultWebpagePreferences(
+      pigeonApi: api, pigeonInstance: instance)
+
+    XCTAssertEqual(value, instance.defaultWebpagePreferences)
+  }
 }

packages/webview_flutter/webview_flutter_wkwebview/darwin/Tests/WebpagePreferencesProxyAPITests.swift

@@ -0,0 +1,23 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import WebKit
+import XCTest
+
+@testable import webview_flutter_wkwebview
+
+class WebpagePreferencesProxyAPITests: XCTestCase {
+  @available(iOS 14.0, macOS 11.0, *)
+  @MainActor func testSetAllowsContentJavaScript() {
+    let registrar = TestProxyApiRegistrar()
+    let api = registrar.apiDelegate.pigeonApiWKWebpagePreferences(registrar)
+
+    let instance = WKWebpagePreferences()
+    let allow = true
+    try? api.pigeonDelegate.setAllowsContentJavaScript(
+      pigeonApi: api, pigeonInstance: instance, allow: allow)
+
+    XCTAssertEqual(instance.allowsContentJavaScript, allow)
+  }
+}

packages/webview_flutter/webview_flutter_wkwebview/darwin/webview_flutter_wkwebview/Sources/webview_flutter_wkwebview/PreferencesProxyAPIDelegate.swift

@@ -12,6 +12,15 @@ class PreferencesProxyAPIDelegate: PigeonApiDelegateWKPreferences {
   func setJavaScriptEnabled(
     pigeonApi: PigeonApiWKPreferences, pigeonInstance: WKPreferences, enabled: Bool
   ) throws {
-    pigeonInstance.javaScriptEnabled = enabled
+    if #available(iOS 14.0, macOS 11.0, *) {
+      // On iOS 14 and macOS 11, WKWebpagePreferences.allowsContentJavaScript should be
+      // used instead.
+      throw (pigeonApi.pigeonRegistrar as! ProxyAPIRegistrar)
+        .createUnsupportedVersionError(
+          method: "WKPreferences.javaScriptEnabled",
+          versionRequirements: "< iOS 14.0, macOS 11.0")
+    } else {
+      pigeonInstance.javaScriptEnabled = enabled
+    }
   }
 }

packages/webview_flutter/webview_flutter_wkwebview/darwin/webview_flutter_wkwebview/Sources/webview_flutter_wkwebview/ProxyAPIRegistrar.swift

@@ -273,4 +273,11 @@ class ProxyAPIDelegate: WebKitLibraryPigeonProxyApiDelegate {
   func pigeonApiURL(_ registrar: WebKitLibraryPigeonProxyApiRegistrar) -> PigeonApiURL {
     return PigeonApiURL(pigeonRegistrar: registrar, delegate: URLProxyAPIDelegate())
   }
+
+  func pigeonApiWKWebpagePreferences(_ registrar: WebKitLibraryPigeonProxyApiRegistrar)
+    -> PigeonApiWKWebpagePreferences
+  {
+    return PigeonApiWKWebpagePreferences(
+      pigeonRegistrar: registrar, delegate: WebpagePreferencesProxyAPIDelegate())
+  }
 }