Add ENV.VIEW_STATE to warn or throw on ViewState usage.

Closes emberjs#6.

README.md

@@ -23,3 +23,4 @@ app more and more Ember-1.0-compatible.
 
  * [Accessors](doc/accessors.md)
  * [Ember.Object.create](doc/object_create.md)
+ * [Ember.ViewState](doc/view_state.md)

doc/view_state.md

@@ -0,0 +1,9 @@
+# Ember.ViewState
+
+In Ember 1.0, `Ember.ViewState` has been removed. This fork introduces a flag, `ENV.VIEW_STATE`, with three allowed values:
+
+ * `null` (the default) -- `Ember.ViewState` works per 0.9.8.1
+ * `"warn"` -- Calling `extend` or `create` will warn
+ * `"1.0"` -- Calling `extend` or `create` will throw
+
+See [issue #6](https://github.com/zendesk/ember.js/issues/6) for more information.

packages/ember-states/tests/backports/view_state_test.js

@@ -0,0 +1,47 @@
+var originalFlag, originalWarn, warnings;
+
+module("Backported Ember.ViewState", {
+  setup: function() {
+    originalFlag = Ember.ENV.VIEW_STATE;
+    originalWarn = Ember.Logger.warn;
+    warnings = [];
+    Ember.Logger.warn = function(msg) {
+      warnings.push(msg.replace("WARNING: ", ""));
+    };
+  },
+  teardown: function() {
+    Ember.ENV.VIEW_STATE = originalFlag;
+    Ember.Logger.warn = originalWarn;
+  }
+});
+
+test("doesn't warn on null level", function() {
+  Ember.ENV.VIEW_STATE = null;
+
+  Ember.ViewState.extend();
+  Ember.ViewState.create();
+  equal(warnings.length, 0);
+});
+
+test("warns on warn level", function() {
+  Ember.ENV.VIEW_STATE = 'warn';
+
+  Ember.ViewState.extend();
+  equal(warnings.length, 1);
+  equal(warnings[0], "Ember.ViewState has been removed from Ember 1.0.");
+  Ember.ViewState.create();
+  equal(warnings.length, 2);
+  equal(warnings[1], "Ember.ViewState has been removed from Ember 1.0.");
+});
+
+test("throws on error level", function() {
+  Ember.ENV.VIEW_STATE = '1.0';
+
+  raises(function() {
+    Ember.ViewState.extend();
+  }, /Ember\.ViewState has been removed from Ember 1\.0\./);
+
+  raises(function() {
+    Ember.ViewState.create();
+  }, /Ember\.ViewState has been removed from Ember 1\.0\./);
+});

packages/ember-viewstates/lib/view_state.js

@@ -46,3 +46,23 @@ Ember.ViewState = Ember.State.extend({
     }
   }
 });
+
+function ensureViewStateAvailable() {
+  var op = {
+    warn: Ember.warn,
+    "1.0": Ember.assert
+  }[Ember.ENV.VIEW_STATE] || Ember.K;
+  op("Ember.ViewState has been removed from Ember 1.0.");
+}
+
+Ember.ViewState.reopenClass({
+  extend: function() {
+    ensureViewStateAvailable();
+    return this._super.apply(this, arguments);
+  },
+
+  create: function() {
+    ensureViewStateAvailable();
+    return this._super.apply(this, arguments);
+  }
+});