Fix crashes in views with optional content (#364)

* Add TokamakStaticHTMLTests target

* Add AnyOptional, clarify conformances issues

.vscode/tasks.json

@@ -11,7 +11,7 @@
     {
       "label": "swift test",
       "type": "shell",
-      "command": "swift test"
+      "command": "swift build --product TokamakPackageTests && `xcrun --find xctest` .build/debug/TokamakPackageTests.xctest"
     },
     {
       "label": "carton dev",

Package.swift

@@ -154,5 +154,14 @@ let package = Package(
       name: "TokamakTests",
       dependencies: ["TokamakTestRenderer"]
     ),
+    // FIXME: re-enable when `ViewDeferredToRenderer` conformance conflicts issue is resolved
+    // Currently, when multiple modules that have conflicting `ViewDeferredToRenderer`
+    // implementations are linked in the same binary, only a single one is used with no defined
+    // behavior for that. We need to replace `ViewDeferredToRenderer` with a different solution
+    // that isn't prone to these hard to debug errors.
+    // .testTarget(
+    //   name: "TokamakStaticHTMLTests",
+    //   dependencies: ["TokamakStaticHTML"]
+    // ),
   ]
 )

Sources/TokamakCore/Views/AnyView.swift

@@ -59,8 +59,16 @@ public struct AnyView: View {
       bodyType = V.Body.self
       self.view = view
       if view is ViewDeferredToRenderer {
+        bodyClosure = {
+          let deferredView: Any
+          if let opt = $0 as? AnyOptional, let value = opt.value {
+            deferredView = value
+          } else {
+            deferredView = $0
+          }
           // swiftlint:disable:next force_cast
-        bodyClosure = { ($0 as! ViewDeferredToRenderer).deferredBody }
+          return (deferredView as! ViewDeferredToRenderer).deferredBody
+        }
       } else {
         // swiftlint:disable:next force_cast
         bodyClosure = { AnyView(($0 as! V).body) }

Sources/TokamakCore/Views/ViewBuilder.swift

@@ -62,6 +62,19 @@ extension Optional: View where Wrapped: View {
   }
 }
 
+protocol AnyOptional {
+  var value: Any? { get }
+}
+
+extension Optional: AnyOptional {
+  var value: Any? {
+    switch self {
+    case let .some(value): return value
+    case .none: return nil
+    }
+  }
+}
+
 @_functionBuilder public enum ViewBuilder {
   public static func buildBlock() -> EmptyView { EmptyView() }
 

Sources/TokamakGTK/Views/TextField.swift

@@ -59,25 +59,29 @@ private func bindAction(to entry: UnsafeMutablePointer<GtkWidget>, textBinding:
 extension SecureField: ViewDeferredToRenderer where Label == Text {
   public var deferredBody: AnyView {
     let proxy = _SecureFieldProxy(self)
-    return AnyView(WidgetView(build: { _ in
+    return AnyView(WidgetView(
+      build: { _ in
         build(textBinding: proxy.textBinding, label: proxy.label, visible: false)
       },
       update: { w in
         guard case let .widget(entry) = w.storage else { return }
         update(entry: entry, textBinding: proxy.textBinding, label: proxy.label)
-    }) {})
+      }
+    ) {})
   }
 }
 
 extension TextField: ViewDeferredToRenderer where Label == Text {
   public var deferredBody: AnyView {
     let proxy = _TextFieldProxy(self)
-    return AnyView(WidgetView(build: { _ in
+    return AnyView(WidgetView(
+      build: { _ in
         build(textBinding: proxy.textBinding, label: proxy.label)
       },
       update: { a in
         guard case let .widget(widget) = a.storage else { return }
         update(entry: widget, textBinding: proxy.textBinding, label: proxy.label)
-    }) {})
+      }
+    ) {})
   }
 }

Tests/TokamakStaticHTMLTests/HTMLTests.swift

@@ -0,0 +1,45 @@
+// Copyright 2020 Tokamak contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+//  Created by Max Desiatov on 07/12/2018.
+//
+
+import TokamakStaticHTML
+import XCTest
+
+final class ReconcilerTests: XCTestCase {
+  struct Model {
+    let text: Text
+  }
+
+  private struct OptionalBody: View {
+    var model: Model?
+
+    var body: some View {
+      if let text = model?.text {
+        VStack {
+          text
+
+          Spacer()
+        }
+      }
+    }
+  }
+
+  func testOptional() {
+    let renderer = StaticHTMLRenderer(OptionalBody(model: Model(text: Text("text"))))
+
+    XCTAssertEqual(renderer.html.count, 2777)
+  }
+}