Fix a bug where we'd parse pre-release constraints as empty (dart-lang/pub_semver#25)

pkgs/pub_semver/CHANGELOG.md

diff --git a/pkgs/pub_semver/CHANGELOG.md b/pkgs/pub_semver/CHANGELOG.md
index 207ba29..0246edd 100644
--- a/pkgs/pub_semver/CHANGELOG.md
+++ b/pkgs/pub_semver/CHANGELOG.md
@@ -1,3 +1,8 @@
+# 1.3.6
+
+* Fix a bug where constraints that only allowed pre-release versions would be
+  parsed as empty constraints.
+
 # 1.3.5
 
 * Fix a bug where `VersionRange.intersect()` would return incorrect results for

pkgs/pub_semver/lib/src/version_constraint.dart

diff --git a/pkgs/pub_semver/lib/src/version_constraint.dart b/pkgs/pub_semver/lib/src/version_constraint.dart
index 36bbd9a..670a928 100644
--- a/pkgs/pub_semver/lib/src/version_constraint.dart
+++ b/pkgs/pub_semver/lib/src/version_constraint.dart
@@ -57,7 +57,7 @@
     if (text == "any") return any;
 
     // Try to parse and consume a version number.
-    matchVersion() {
+    Version matchVersion() {
       var version = START_VERSION.firstMatch(text);
       if (version == null) return null;
 
@@ -66,7 +66,7 @@
     }
 
     // Try to parse and consume a comparison operator followed by a version.
-    matchComparison() {
+    VersionRange matchComparison() {
       var comparison = START_COMPARISON.firstMatch(text);
       if (comparison == null) return null;
 
@@ -117,35 +117,55 @@
     var compatibleWith = matchCompatibleWith();
     if (compatibleWith != null) return compatibleWith;
 
-    var constraints = <VersionConstraint>[];
+    Version min;
+    var includeMin = false;
+    Version max;
+    var includeMax = false;
 
     while (true) {
       skipWhitespace();
 
       if (text.isEmpty) break;
 
-      var version = matchVersion();
-      if (version != null) {
-        constraints.add(version);
-        continue;
+      var newRange = matchVersion() ?? matchComparison();
+      if (newRange == null) {
+        throw new FormatException('Could not parse version "$originalText". '
+            'Unknown text at "$text".');
       }
 
-      var comparison = matchComparison();
-      if (comparison != null) {
-        constraints.add(comparison);
-        continue;
+      if (newRange.min != null) {
+        if (min == null || newRange.min > min) {
+          min = newRange.min;
+          includeMin = newRange.includeMin;
+        } else if (newRange.min == min && !newRange.includeMin) {
+          includeMin = false;
+        }
       }
 
-      // If we got here, we couldn't parse the remaining string.
-      throw new FormatException('Could not parse version "$originalText". '
-          'Unknown text at "$text".');
+      if (newRange.max != null) {
+        if (max == null || newRange.max < max) {
+          max = newRange.max;
+          includeMax = newRange.includeMax;
+        } else if (newRange.max == max && !newRange.includeMax) {
+          includeMax = false;
+        }
+      }
     }
 
-    if (constraints.isEmpty) {
+    if (min == null && max == null) {
       throw new FormatException('Cannot parse an empty string.');
     }
 
-    return new VersionConstraint.intersection(constraints);
+    if (min != null && max != null) {
+      if (min > max) return VersionConstraint.empty;
+      if (min == max) {
+        if (includeMin && includeMax) return min;
+        return VersionConstraint.empty;
+      }
+    }
+
+    return new VersionRange(
+        min: min, includeMin: includeMin, max: max, includeMax: includeMax);
   }
 
   /// Creates a version constraint which allows all versions that are

pkgs/pub_semver/pubspec.yaml

diff --git a/pkgs/pub_semver/pubspec.yaml b/pkgs/pub_semver/pubspec.yaml
index 4dbabe4..1b0beb8 100644
--- a/pkgs/pub_semver/pubspec.yaml
+++ b/pkgs/pub_semver/pubspec.yaml
@@ -1,5 +1,5 @@
 name: pub_semver
-version: 1.3.5
+version: 1.3.6
 author: Dart Team <misc@dartlang.org>
 description: >
  Versions and version constraints implementing pub's versioning policy. This

pkgs/pub_semver/test/version_constraint_test.dart

diff --git a/pkgs/pub_semver/test/version_constraint_test.dart b/pkgs/pub_semver/test/version_constraint_test.dart
index bc37832..bf3a018 100644
--- a/pkgs/pub_semver/test/version_constraint_test.dart
+++ b/pkgs/pub_semver/test/version_constraint_test.dart
@@ -103,6 +103,18 @@
               new Version.parse('1.3.0'), new Version.parse('3.4.5')));
     });
 
+    test('parses a pre-release-only constraint', () {
+      var constraint = new VersionConstraint.parse('>=1.0.0-dev.2 <1.0.0');
+      expect(
+          constraint,
+          allows(new Version.parse('1.0.0-dev.2'),
+              new Version.parse('1.0.0-dev.3')));
+      expect(
+          constraint,
+          doesNotAllow(
+              new Version.parse('1.0.0-dev.1'), new Version.parse('1.0.0')));
+    });
+
     test('ignores whitespace around comparison operators', () {
       var constraint = new VersionConstraint.parse(' >1.0.0>=1.2.3 < 1.3.0');