Don't crash on surrogate pairs. (#5)

Closes flutter#4

Author: nex3

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.0.2
+
+* `SpanScanner` no longer crashes when creating a span that contains a UTF-16
+  surrogate pair.
+
 ## 1.0.1
 
 * Fix the error text emitted by `StringScanner.expectChar()`.

lib/src/span_scanner.dart

@@ -56,7 +56,7 @@ class SpanScanner extends StringScanner implements LineScanner {
   /// [FileSpan]s as well as for error reporting. It can be a [String], a
   /// [Uri], or `null`.
   SpanScanner(String string, {sourceUrl, int position})
-      : _sourceFile = new SourceFile(string, url: sourceUrl),
+      : _sourceFile = new SourceFile.fromString(string, url: sourceUrl),
         super(string, sourceUrl: sourceUrl, position: position);
 
   /// Creates a new [SpanScanner] that eagerly computes line and column numbers.

lib/src/string_scanner.dart

@@ -204,7 +204,7 @@ class StringScanner {
     }
     if (length == null) length = match == null ? 0 : match.end - match.start;
 
-    var sourceFile = new SourceFile(string, url: sourceUrl);
+    var sourceFile = new SourceFile.fromString(string, url: sourceUrl);
     var span = sourceFile.span(position, position + length);
     throw new StringScannerException(message, span, string);
   }

pubspec.yaml

@@ -1,12 +1,12 @@
 name: string_scanner
-version: 1.0.1
+version: 1.0.2
 author: "Dart Team <[email protected]>"
 homepage: https://github.com/dart-lang/string_scanner
 description: >
   A class for parsing strings using a sequence of patterns.
 dependencies:
   charcode: "^1.1.0"
-  source_span: "^1.0.0"
+  source_span: "^1.4.0"
 dev_dependencies:
   test: ">=0.12.0 <0.13.0"
 environment:

test/span_scanner_test.dart

@@ -9,12 +9,13 @@ import 'package:test/test.dart';
 import 'utils.dart';
 
 void main() {
-  testForImplementation("lazy", () {
-    return new SpanScanner('foo\nbar\nbaz', sourceUrl: 'source');
+  testForImplementation("lazy", ([string]) {
+    return new SpanScanner(string ?? 'foo\nbar\nbaz', sourceUrl: 'source');
   });
 
-  testForImplementation("eager", () {
-    return new SpanScanner.eager('foo\nbar\nbaz', sourceUrl: 'source');
+  testForImplementation("eager", ([string]) {
+    return new SpanScanner.eager(string ?? 'foo\nbar\nbaz',
+        sourceUrl: 'source');
   });
 
   group("within", () {
@@ -23,7 +24,7 @@ void main() {
 
     var scanner;
     setUp(() {
-      var file = new SourceFile(text, url: 'source');
+      var file = new SourceFile.fromString(text, url: 'source');
       scanner = new SpanScanner.within(
           file.span(startOffset, text.indexOf(' :after')));
     });
@@ -136,6 +137,15 @@ void testForImplementation(String name, SpanScanner create()) {
       expect(span.text, equals('o\nbar\nba'));
     });
 
+    test(".spanFrom() handles surrogate pairs correctly", () {
+      scanner = create('fo\u{12345}o');
+      scanner.scan('fo');
+      var state = scanner.state;
+      scanner.scan('\u{12345}o');
+      var span = scanner.spanFrom(state);
+      expect(span.text, equals('\u{12345}o'));
+    });
+
     test(".emptySpan returns an empty span at the current location", () {
       scanner.scan('foo\nba');