Jump past disjoint package on disjoint constraint.

sdk/lib/_internal/pub/test/version_solver_test.dart

 // Copyright (c) 2012, 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.
 
 library pub_update_test;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:unittest/unittest.dart';
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     }
   }
 
   testResolve('complex backtrack', map, result: {
     'myapp from root': '0.0.0',
     'foo': '0.9.0',
     'bar': '9.0.0',
     'baz': '0.0.0'
   }, maxTries: 100);
 
+  // If there's a disjoint constraint on a package, then selecting other
+  // versions of it is a waste of time: no possible versions can match. We need
+  // to jump past it to the most recent package that affected the constraint.
+  testResolve('backjump past failed package on disjoint constraint', {
+    'myapp 0.0.0': {
+      'a': 'any',
+      'foo': '>2.0.0'
+    },
+    'a 1.0.0': {
+      'foo': 'any' // ok
+    },
+    'a 2.0.0': {
+      'foo': '<1.0.0' // disjoint with myapp's constraint on foo
+    },
+    'foo 2.0.0': {},
+    'foo 2.0.1': {},
+    'foo 2.0.2': {},
+    'foo 2.0.3': {},
+    'foo 2.0.4': {}
+  }, result: {
+    'myapp from root': '0.0.0',
+    'a': '1.0.0',
+    'foo': '2.0.4'
+  }, maxTries: 2);
+
   // TODO(rnystrom): More tests. In particular:
   // - Tests that demonstrate backtracking for every case that can cause a
   //   solution to fail (no versions, disjoint, etc.)
   // - Tests where there are multiple valid solutions and "best" is possibly
   //   ambiguous to nail down which order the backtracker tries solutions.
 }
 
 sdkConstraint() {
   var badVersion = '0.0.0-nope';
   var goodVersion = sdk.version.toString();
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   var source = "mock1";
   var match = new RegExp(r"(.*) from (.*)").firstMatch(description);
   if (match != null) {
     name = match[1];
     source = match[2];
     if (source == "root") source = null;
   }
 
   callback(isDev, name, source);
 }