Improve the YamlScalar.span values with trailing whitespace

Fixes https://github.com/dart-lang/yaml/issues/51

Also remove dead line from changelog

pkgs/yaml/CHANGELOG.md

diff --git a/pkgs/yaml/CHANGELOG.md b/pkgs/yaml/CHANGELOG.md
index 143e1c2..c0b3063 100644
--- a/pkgs/yaml/CHANGELOG.md
+++ b/pkgs/yaml/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 2.1.16
+
+* Improve the `span` associated with `YamlScalar` values with trailing
+  whitespace.
+
 ## 2.1.15
 
 * Set max SDK version to `<3.0.0`, and adjust other dependencies.
@@ -110,12 +115,10 @@
   constructors make it possible to use the same API to access non-YAML data as
   YAML data.
 
-* Make `YamlException` inherit from source_map's [`SpanFormatException`][]. This
+* Make `YamlException` inherit from source_map's `SpanFormatException`. This
   improves the error formatting and allows callers access to source range
   information.
 
-[SpanFormatException]: (http://www.dartdocs.org/documentation/source_maps/0.9.2/index.html#source_maps/source_maps.SpanFormatException)
-
 ## 1.0.0+1
 
 * Fix a variable name typo.

pkgs/yaml/lib/src/parser.dart

diff --git a/pkgs/yaml/lib/src/parser.dart b/pkgs/yaml/lib/src/parser.dart
index bffaa17..0971e7f 100644
--- a/pkgs/yaml/lib/src/parser.dart
+++ b/pkgs/yaml/lib/src/parser.dart
@@ -303,7 +303,22 @@
 
       _state = _states.removeLast();
       _scanner.scan();
-      return ScalarEvent(span.expand(token.span), token.value, token.style,
+
+      span = span.expand(token.span);
+      if (span.text != token.value) {
+        // If the only difference between the span and the token is trailing
+        // whitespace
+        if (span.text.trimRight() == token.value) {
+          span = span.file.span(
+            span.start.offset,
+            // TODO(kevmoo): The length of `token.value` may be incorrect
+            // with some UNICODE values. Find a more clean solution.
+            span.start.offset + token.value.length,
+          );
+        }
+      }
+
+      return ScalarEvent(span, token.value, token.style,
           anchor: anchor, tag: tag);
     }
 

pkgs/yaml/pubspec.yaml

diff --git a/pkgs/yaml/pubspec.yaml b/pkgs/yaml/pubspec.yaml
index da41f3a..d0fb672 100644
--- a/pkgs/yaml/pubspec.yaml
+++ b/pkgs/yaml/pubspec.yaml
@@ -1,5 +1,5 @@
 name: yaml
-version: 2.1.16-dev
+version: 2.1.16
 
 description: A parser for YAML.
 author: Dart Team <misc@dartlang.org>

pkgs/yaml/test/span_test.dart

diff --git a/pkgs/yaml/test/span_test.dart b/pkgs/yaml/test/span_test.dart
index 7ef61d3..09e461c 100644
--- a/pkgs/yaml/test/span_test.dart
+++ b/pkgs/yaml/test/span_test.dart
@@ -8,13 +8,6 @@
 import 'package:test/test.dart';
 import 'package:yaml/yaml.dart';
 
-void _expectSpan(SourceSpan source, String expected) {
-  final result = source.message('message');
-  printOnFailure("r'''\n$result'''");
-
-  expect(result, expected);
-}
-
 void main() {
   YamlMap yaml;
 
@@ -33,7 +26,6 @@
     _expectSpan(
       yaml.nodes['num'].span,
       r'''
-line 2, column 9: message
   ╷
 2 │  "num": 42,
   │         ^^
@@ -45,7 +37,6 @@
     _expectSpan(
       yaml.nodes['null'].span,
       r'''
-line 7, column 10: message
   ╷
 7 │  "null": null
   │          ^^^^
@@ -64,7 +55,6 @@
       _expectSpan(
         nestedMap.nodes['null'].span,
         r'''
-line 4, column 11: message
   ╷
 4 │   "null": null,
   │           ^^^^
@@ -76,14 +66,15 @@
       _expectSpan(
         nestedMap.nodes['num'].span,
         r'''
-line 5, column 10: message
   ╷
-5 │     "num": 42
-  │ ┌──────────^
-6 │ │  },
-  │ └─^
+5 │   "num": 42
+  │          ^^
   ╵''',
       );
     });
   });
 }
+
+void _expectSpan(SourceSpan source, String expected) {
+  expect(source.highlight(), expected);
+}