Add a sass.types.Error constructor to the JS API (#627)

Closes #590

CHANGELOG.md

@@ -3,6 +3,11 @@
 * Consistently parse U+000C FORM FEED, U+000D CARRIAGE RETURN, and sequences of
   U+000D CARRIAGE RETURN followed by U+000A LINE FEED as individual newlines.
 
+### JavaScript API
+
+* Add a `sass.types.Error` constructor as an alias for `Error`. This makes our
+  custom function API compatible with Node Sass's.
+
 ## 1.17.3
 
 * Fix an edge case where slash-separated numbers were written to the stylesheet

lib/src/node.dart

@@ -56,7 +56,8 @@ void main() {
       Map: mapConstructor,
       Null: nullConstructor,
       Number: numberConstructor,
-      String: stringConstructor);
+      String: stringConstructor,
+      Error: jsErrorConstructor);
 }
 
 /// Converts Sass to CSS.

lib/src/node/types.dart

@@ -14,6 +14,8 @@ class Types {
   external set Null(function);
   external set Number(function);
   external set String(function);
+  external set Error(function);
 
-  external factory Types({Boolean, Color, List, Map, Null, Number, String});
+  external factory Types(
+      {Boolean, Color, List, Map, Null, Number, String, Error});
 }

lib/src/node/utils.dart

@@ -34,10 +34,10 @@ bool isUndefined(value) => _isUndefined.call(value) as bool;
 final _isUndefined = JSFunction("value", "return value === undefined;");
 
 @JS("Error")
-external Function get _JSError;
+external Function get jsErrorConstructor;
 
 /// Returns whether [value] is a JS Error object.
-bool isJSError(value) => instanceof(value, _JSError);
+bool isJSError(value) => instanceof(value, jsErrorConstructor);
 
 /// Invokes [function] with [thisArg] as `this`.
 Object call2(JSFunction function, Object thisArg, Object arg1, Object arg2) =>

lib/src/node/value.dart

@@ -5,6 +5,7 @@
 import 'dart:js_util';
 
 import '../value.dart';
+import 'utils.dart';
 import 'value/color.dart';
 import 'value/list.dart';
 import 'value/map.dart';
@@ -20,11 +21,14 @@ export 'value/number.dart';
 export 'value/string.dart';
 
 /// Unwraps a value wrapped with [wrapValue].
+///
+/// If [object] is a JS error, throws it.
 Value unwrapValue(object) {
   if (object != null) {
     if (object is Value) return object;
     var value = getProperty(object, 'dartValue');
     if (value != null && value is Value) return value;
+    if (isJSError(object)) throw object;
   }
   throw "$object must be a Sass value type.";
 }

package.json

@@ -4,6 +4,7 @@
     "install dependencies used for testing the Node API."
   ],
   "devDependencies": {
+    "node-sass": "^4.11.0",
     "chokidar": "^2.0.0",
     "fibers": ">=1.0.0 <4.0.0",
     "intercept-stdout": "^0.1.2"

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.17.4-dev
+version: 1.17.4
 description: A Sass implementation in Dart.
 author: Dart Team <[email protected]>
 homepage: https://github.com/sass/dart-sass

test/node_api/api.dart

@@ -75,6 +75,7 @@ class SassTypes {
   external NodeSassNullClass get Null;
   external Function get Number;
   external Function get String;
+  external Function get Error;
 }
 
 @JS()

test/node_api/function_test.dart

@@ -195,6 +195,16 @@ void main() {
       expect(error.toString(), contains('aw beans'));
     });
 
+    test("reports a synchronous sass.types.Error", () async {
+      var error = await renderError(RenderOptions(
+          data: "a {b: foo()}",
+          functions: jsify({
+            "foo": allowInterop(
+                (_) => callConstructor(sass.types.Error, ["aw beans"]))
+          })));
+      expect(error.toString(), contains('aw beans'));
+    });
+
     test("reports an asynchronous error", () async {
       var error = await renderError(RenderOptions(
           data: "a {b: foo()}",
@@ -208,6 +218,19 @@ void main() {
       expect(error.toString(), contains('aw beans'));
     });
 
+    test("reports an asynchronous sass.types.Error", () async {
+      var error = await renderError(RenderOptions(
+          data: "a {b: foo()}",
+          functions: jsify({
+            "foo": allowInterop((done) {
+              Future.delayed(Duration.zero).then((_) {
+                done(callConstructor(sass.types.Error, ["aw beans"]));
+              });
+            })
+          })));
+      expect(error.toString(), contains('aw beans'));
+    });
+
     test("reports a null return", () async {
       var error = await renderError(RenderOptions(
           data: "a {b: foo()}",