Make VersionRange implement Comparable.

test/version_range_test.dart

Index: test/version_range_test.dart
diff --git a/test/version_range_test.dart b/test/version_range_test.dart
index 9eaa980464cf3329f244213b4eb2a36abae36e84..eaa473f033aba2ce71d14b743a96842305bab8f8 100644
--- a/test/version_range_test.dart
+++ b/test/version_range_test.dart
@@ -445,4 +445,61 @@ main() {
     expect(new VersionRange().isEmpty, isFalse);
     expect(new VersionRange(min: v123, max: v124).isEmpty, isFalse);
   });
+
+  group('compareTo()', () {
+    test("orders by minimum first", () {
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v080),
+          new VersionRange(min: v010, max: v072));
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v080),
+          new VersionRange(min: v010, max: v080));
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v080),
+          new VersionRange(min: v010, max: v114));
+    });
+
+    test("orders by maximum second", () {
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v010),
+          new VersionRange(min: v003, max: v072));
+    });
+
+    test("includeMin comes before !includeMin", () {
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v080, includeMin: true),
+          new VersionRange(min: v003, max: v080, includeMin: false));
+    });
+
+    test("includeMax comes after !includeMax", () {
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v080, includeMax: false),
+          new VersionRange(min: v003, max: v080, includeMax: true));
+    });
+
+    test("no minimum comes before small minimum", () {
+      _expectComparesSmaller(
+          new VersionRange(max: v010),
+          new VersionRange(min: v003, max: v010));
+      _expectComparesSmaller(
+          new VersionRange(max: v010, includeMin: true),

[Bob Nystrom, 2016/06/03 16:18:03]

What's the difference between this and the previous test? Doesn't not having a
minimum imply "includeMin"? What would an exclusive min mean if there is no
minimum?

[nweiz, 2016/06/06 22:27:46]

This *should* be the same as the last test, but VersionRange stores [includeMin]
as `true` or `false` even if [min] is `null`. This verifies that a different
boolean flag there doesn't affect the comparison.

+          new VersionRange(min: v003, max: v010));
+    });
+
+    test("no maximium comes after large maximum", () {
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v300),
+          new VersionRange(min: v003));
+      _expectComparesSmaller(
+          new VersionRange(min: v003, max: v300),
+          new VersionRange(min: v003, includeMax: true));
+    });
+  });
+}
+
+void _expectComparesSmaller(VersionRange smaller, VersionRange larger) {
+  expect(smaller.compareTo(larger), lessThan(0),
+      reason: "expected $smaller to sort below $larger");
+  expect(larger.compareTo(smaller), greaterThan(0),
+      reason: "expected $larger to sort above $smaller");
 }