From 8fd211d789aeb80824890a315f57dd6d4ccfb7cb Mon Sep 17 00:00:00 2001
From: Natalie Weizenbaum <nex342@gmail.com>
Date: Sat, 2 Dec 2017 15:02:37 -0800
Subject: [PATCH] Clean up UTF-8 error handling in Dart

---
 lib/src/io/vm.dart | 21 ++++++++-------------
 pubspec.yaml       |  2 +-
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/lib/src/io/vm.dart b/lib/src/io/vm.dart
index 9471170f..565b15aa 100644
--- a/lib/src/io/vm.dart
+++ b/lib/src/io/vm.dart
@@ -26,21 +26,16 @@ String readFile(String path) {
 
   try {
     return UTF8.decode(bytes);
-  } on FormatException {
+  } on FormatException catch (error) {
+    var decodedUntilError =
+        UTF8.decode(bytes.sublist(0, error.offset), allowMalformed: true);
+    var stringOffset = decodedUntilError.length;
+    if (decodedUntilError.endsWith("�")) stringOffset--;
+
     var decoded = UTF8.decode(bytes, allowMalformed: true);
     var sourceFile = new SourceFile.fromString(decoded, url: p.toUri(path));
-
-    // TODO(nweiz): Use [FormatException.offset] instead when
-    // dart-lang/sdk#28293 is fixed.
-    for (var i = 0; i < bytes.length; i++) {
-      if (decoded.codeUnitAt(i) != 0xFFFD) continue;
-      throw new SassException(
-          "Invalid UTF-8.", sourceFile.location(i).pointSpan());
-    }
-
-    // This should be unreachable, but we'll rethrow the original exception just
-    // in case.
-    rethrow;
+    throw new SassException(
+        "Invalid UTF-8.", sourceFile.location(stringOffset).pointSpan());
   }
 }
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 84518446..7c3bb5e9 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -8,7 +8,7 @@ executables:
   dart-sass: sass
 
 environment:
-  sdk: '>=1.21.0 <2.0.0'
+  sdk: '>=1.22.0 <2.0.0'
 
 dependencies:
   args: "^0.13.0"