Extract out a source_span package from source_maps.

pkg/source_span/test/source_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;
+  setUp(() {
+    span = new SourceSpan(
+        new SourceLocation(5, sourceUrl: "foo.dart"),
+        new SourceLocation(12, sourceUrl: "foo.dart"),
+        "foo bar");
+  });
+
+  group('errors', () {
+    group('for new SourceSpan()', () {
+      test('source URLs must match', () {
+        var start = new SourceLocation(0, sourceUrl: "foo.dart");
+        var end = new SourceLocation(1, sourceUrl: "bar.dart");
+        expect(() => new SourceSpan(start, end, "_"), throwsArgumentError);
+      });
+
+      test('end must come after start', () {
+        var start = new SourceLocation(1);
+        var end = new SourceLocation(0);
+        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 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);
+      });
+
+      test('spans may not be disjoint', () {
+        var other = new SourceSpan(
+            new SourceLocation(13, sourceUrl: 'foo.dart'),
+            new SourceLocation(14, sourceUrl: 'foo.dart'),
+            "_");
+
+        expect(() => span.union(other), throwsArgumentError);
+      });
+    });
+
+    test('for compareTo() source URLs must match', () {
+      var other = new SourceSpan(
+          new SourceLocation(12, sourceUrl: "bar.dart"),
+          new SourceLocation(13, sourceUrl: "bar.dart"),
+          "_");
+
+      expect(() => span.compareTo(other), throwsArgumentError);
+    });
+  });
+
+  test('fields work correctly', () {
+    expect(span.start, equals(new SourceLocation(5, sourceUrl: "foo.dart")));
+    expect(span.end, equals(new SourceLocation(12, sourceUrl: "foo.dart")));
+    expect(span.sourceUrl, equals(Uri.parse("foo.dart")));
+    expect(span.length, equals(7));
+  });
+
+  group("union()", () {
+    test("works with a preceding adjacent span", () {
+      var other = new SourceSpan(
+          new SourceLocation(0, sourceUrl: "foo.dart"),
+          new SourceLocation(5, sourceUrl: "foo.dart"),
+          "hey, ");
+
+      var result = span.union(other);
+      expect(result.start, equals(other.start));
+      expect(result.end, equals(span.end));
+      expect(result.text, equals("hey, foo bar"));
+    });
+
+    test("works with a preceding overlapping span", () {
+      var other = new SourceSpan(
+          new SourceLocation(0, sourceUrl: "foo.dart"),
+          new SourceLocation(8, sourceUrl: "foo.dart"),
+          "hey, foo");
+
+      var result = span.union(other);
+      expect(result.start, equals(other.start));
+      expect(result.end, equals(span.end));
+      expect(result.text, equals("hey, foo bar"));
+    });
+
+    test("works with a following adjacent span", () {
+      var other = new SourceSpan(
+          new SourceLocation(12, sourceUrl: "foo.dart"),
+          new SourceLocation(16, sourceUrl: "foo.dart"),
+          " baz");
+
+      var result = span.union(other);
+      expect(result.start, equals(span.start));
+      expect(result.end, equals(other.end));
+      expect(result.text, equals("foo bar baz"));
+    });
+
+    test("works with a following overlapping span", () {
+      var other = new SourceSpan(
+          new SourceLocation(9, sourceUrl: "foo.dart"),
+          new SourceLocation(16, sourceUrl: "foo.dart"),
+          "bar baz");
+
+      var result = span.union(other);
+      expect(result.start, equals(span.start));
+      expect(result.end, equals(other.end));
+      expect(result.text, equals("foo bar baz"));
+    });
+
+    test("works with an internal overlapping span", () {
+      var other = new SourceSpan(
+          new SourceLocation(7, sourceUrl: "foo.dart"),
+          new SourceLocation(10, sourceUrl: "foo.dart"),
+          "o b");
+
+      expect(span.union(other), equals(span));
+    });
+
+    test("works with an external overlapping span", () {
+      var other = new SourceSpan(
+          new SourceLocation(0, sourceUrl: "foo.dart"),
+          new SourceLocation(16, sourceUrl: "foo.dart"),
+          "hey, foo bar baz");
+
+      expect(span.union(other), equals(other));
+    });
+  });
+
+  group("message()", () {

[Siggi Cherem (dart-lang), 2014/07/16 21:26:10]

Let's bring back some of the tests we have in the source_maps package. We had a
lot of subtle bugs in the past and many of those tests were there as regression
coverage. In particular: 
 - tests for getLine/getColumn for every character of the source text (we
automated that process that given the line + column + line-starts computes the
offset, then verify that calling getLine/getColumn returns the same as the
input.

 - putting the '^' correctly in the right column
 - putting the '^' and terminating the line correctly if the span is in the last
line of a source file (this was actually trick the first time we did this)

There are probably more that I can't remember, so it might be a good idea to
copy a few tests from there. Many of the tests used a file that had digits as
data. This was useful to easily validate the columns you use in the spans match,
since they would also match the numbers in the text.

[nweiz, 2014/07/17 20:22:08]

I'm not a big fan of automating test generation like this. I find it obfuscates
the specific cases that are likely to be problematic; I prefer calling out those
cases explicitly in test descriptions like I do here. If there are specific
cases beyond those I have there that you think should be tested, I'll add
individual tests for them, but I'd rather not add a test for every character in
a file.
There are tests for both of these in file_message_test.
I think I tested all the tricky cases, but if I missed one let me know.

[Siggi Cherem (dart-lang), 2014/07/17 22:24:39]

ok - one that just crossed my mind is to test `file.message` for a file that has
a single line without an EOL. This might be similar to your test with the empty
file + location point, but for a span.

[nweiz, 2014/07/17 23:18:15]

Done.

+    test("prints the text being described", () {
+      expect(span.message("oh no"), equalsIgnoringWhitespace("""

[Siggi Cherem (dart-lang), 2014/07/16 21:26:10]

I'd remove the 'equalsIgnoringWhitespace and just remove a few leading
characters. In the current test the underline ^^ could be off below and we
wouldn't be able to tell.

[nweiz, 2014/07/17 20:22:08]

Done.

+        line 1, column 6 of foo.dart: oh no
+        foo bar
+        ^^^^^^^
+      """));
+    });
+
+    test("gracefully handles a missing source URL", () {
+      var span = new SourceSpan(
+          new SourceLocation(5), new SourceLocation(12), "foo bar");
+
+      expect(span.message("oh no"), equalsIgnoringWhitespace("""
+        line 1, column 6: oh no
+        foo bar
+        ^^^^^^^
+      """));
+    });
+
+    test("gracefully handles empty text", () {
+      var span = new SourceSpan(
+          new SourceLocation(5), new SourceLocation(5), "");
+
+      expect(span.message("oh no"),
+          equals("line 1, column 6: oh no"));
+    });
+
+    test("doesn't colorize if color is false", () {
+      expect(span.message("oh no", color: false),
+          equalsIgnoringWhitespace("""
+        line 1, column 6 of foo.dart: oh no
+        foo bar
+        ^^^^^^^
+      """));
+    });
+
+    test("colorizes if color is true", () {
+      expect(span.message("oh no", color: true),
+          equalsIgnoringWhitespace("""
+        line 1, column 6 of foo.dart: oh no
+        ${colors.RED}foo bar
+        ^^^^^^^${colors.NONE}
+      """));
+    });
+
+    test("uses the given color if it's passed", () {
+      expect(span.message("oh no", color: colors.YELLOW),
+          equalsIgnoringWhitespace("""
+        line 1, column 6 of foo.dart: oh no
+        ${colors.YELLOW}foo bar
+        ^^^^^^^${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));
+    });
+
+    test("sorts by length second", () {
+      var other = new SourceSpan(
+          new SourceLocation(5, sourceUrl: "foo.dart"),
+          new SourceLocation(14, sourceUrl: "foo.dart"),
+          "foo bar b");
+
+      expect(span.compareTo(other), lessThan(0));
+      expect(other.compareTo(span), greaterThan(0));
+    });
+
+    test("considers equal spans equal", () {
+      expect(span.compareTo(span), equals(0));
+    });
+  });
+
+  group("equality", () {
+    test("two spans with the same locations are equal", () {
+      var other = new SourceSpan(
+          new SourceLocation(5, sourceUrl: "foo.dart"),
+          new SourceLocation(12, sourceUrl: "foo.dart"),
+          "foo bar");
+
+      expect(span, equals(other));
+    });
+
+    test("a different start isn't equal", () {
+      var other = new SourceSpan(
+          new SourceLocation(0, sourceUrl: "foo.dart"),
+          new SourceLocation(12, sourceUrl: "foo.dart"),
+          "hey, foo bar");
+
+      expect(span, isNot(equals(other)));
+    });
+
+    test("a different end isn't equal", () {
+      var other = new SourceSpan(
+          new SourceLocation(5, sourceUrl: "foo.dart"),
+          new SourceLocation(16, sourceUrl: "foo.dart"),
+          "foo bar baz");
+
+      expect(span, isNot(equals(other)));
+    });
+
+    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)));
+    });
+  });
+}