Introduce span with line context

test/span_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:unittest/unittest.dart';
 import 'package:source_span/source_span.dart';
 import 'package:source_span/src/colors.dart' as colors;
 
 main() {
   var span;
@@ skipping 18 matching lines @@
         expect(() => new SourceSpan(start, end, "_"), throwsArgumentError);
       });
 
       test('text must be the right length', () {
         var start = new SourceLocation(0);
         var end = new SourceLocation(1);
         expect(() => new SourceSpan(start, end, "abc"), throwsArgumentError);
       });
     });
 
+    group('for new SourceSpanWithContext()', () {
+      test('context must contain text', () {
+        var start = new SourceLocation(2);
+        var end = new SourceLocation(5);
+        expect(() => new SourceSpanWithContext(
+              start, end, "abc", "--axc--"), throwsArgumentError);
+      });
+
+      test('text starts at start.column in context', () {
+        var start = new SourceLocation(3);
+        var end = new SourceLocation(5);
+        expect(() => new SourceSpanWithContext(
+              start, end, "abc", "--abc--"), throwsArgumentError);
+      });
+
+      test('text starts at start.column of line in multi-line context', () {
+        var start = new SourceLocation(4, line: 55, column: 3);
+        var end = new SourceLocation(7, line: 55, column: 6);
+        expect(() => new SourceSpanWithContext(
+              start, end, "abc", "\n--abc--"), throwsArgumentError);
+        expect(() => new SourceSpanWithContext(
+              start, end, "abc", "\n----abc--"), throwsArgumentError);
+        expect(() => new SourceSpanWithContext(
+              start, end, "abc", "\n\n--abc--"), throwsArgumentError);
+
+        // However, these are valid:
+        new SourceSpanWithContext(start, end, "abc", "\n---abc--");
+        new SourceSpanWithContext(start, end, "abc", "\n\n---abc--");
+      });
+    });
+
     group('for union()', () {
       test('source URLs must match', () {
         var other = new SourceSpan(
             new SourceLocation(12, sourceUrl: "bar.dart"),
             new SourceLocation(13, sourceUrl: "bar.dart"),
             "_");
 
         expect(() => span.union(other), throwsArgumentError);
       });
 
@@ skipping 122 matching lines @@
       expect(span.message("oh no", color: false), equals("""
 line 1, column 6 of foo.dart: oh no
 foo bar
 ^^^^^^^"""));
     });
 
     test("colorizes if color is true", () {
       expect(span.message("oh no", color: true),
           equals("""
 line 1, column 6 of foo.dart: oh no
-${colors.RED}foo bar
-^^^^^^^${colors.NONE}"""));
+${colors.RED}foo bar${colors.NONE}
+${colors.RED}^^^^^^^${colors.NONE}"""));
     });
 
     test("uses the given color if it's passed", () {
       expect(span.message("oh no", color: colors.YELLOW), equals("""
 line 1, column 6 of foo.dart: oh no
-${colors.YELLOW}foo bar
-^^^^^^^${colors.NONE}"""));
+${colors.YELLOW}foo bar${colors.NONE}
+${colors.YELLOW}^^^^^^^${colors.NONE}"""));
     });
   });
 
+  group("message() with context", () {
+    var spanWithContext;
+    setUp(() {
+      spanWithContext = new SourceSpanWithContext(
+          new SourceLocation(5, sourceUrl: "foo.dart"),
+          new SourceLocation(12, sourceUrl: "foo.dart"),
+          "foo bar",
+          "-----foo bar-----");
+    });
+
+    test("underlines under the right column", () {
+      expect(spanWithContext.message("oh no", color: colors.YELLOW), equals("""
+line 1, column 6 of foo.dart: oh no
+-----${colors.YELLOW}foo bar${colors.NONE}-----
+     ${colors.YELLOW}^^^^^^^${colors.NONE}"""));
+    });
+
+    test("supports lines of preceeding context", () {
+      var span = new SourceSpanWithContext(
+          new SourceLocation(5, line: 3, column: 5, sourceUrl: "foo.dart"),
+          new SourceLocation(12, line: 3, column: 12, sourceUrl: "foo.dart"),
+          "foo bar",
+          "previous\nlines\n-----foo bar-----\nfollowing line\n");
+
+      expect(span.message("oh no", color: colors.YELLOW), equals("""
+line 4, column 6 of foo.dart: oh no
+previous
+lines
+-----${colors.YELLOW}foo bar${colors.NONE}-----
+     ${colors.YELLOW}^^^^^^^${colors.NONE}"""));
+    });
+  });
+
   group("compareTo()", () {
     test("sorts by start location first", () {
       var other = new SourceSpan(
           new SourceLocation(6, sourceUrl: "foo.dart"),
           new SourceLocation(14, sourceUrl: "foo.dart"),
           "oo bar b");
 
       expect(span.compareTo(other), lessThan(0));
       expect(other.compareTo(span), greaterThan(0));
     });
@@ skipping 44 matching lines @@
     test("a different source URL isn't equal", () {
       var other = new SourceSpan(
           new SourceLocation(5, sourceUrl: "bar.dart"),
           new SourceLocation(12, sourceUrl: "bar.dart"),
           "foo bar");
 
       expect(span, isNot(equals(other)));
     });
   });
 }