Prevent "Spaces" field from being set to inconsistent values

Summary:
At least for now, the "Space" field is just a subfield of the "Visible To" field, so:

  - it doesn't get any separate settings; and
  - it always uses the "Visible To" settings.

Test Plan:
  - Created a form with a hidden view policy field.
  - Created stuff with no "you must pick a space" errors.
  - Created stuff with a normal form.
  - Prefilled "Space" on a noraml form.
  - Verified that trying to prefill "Space" on a form with "Visible To" hidden does nothing.

Reviewers: chad

Reviewed By: chad

Differential Revision: https://secure.phabricator.com/D14812

src/applications/policy/editor/PhabricatorPolicyEditEngineExtension.php

@@ -101,6 +101,7 @@ final class PhabricatorPolicyEditEngineExtension
               ->setLabel(pht('Space'))
               ->setEditTypeKey('space')
               ->setIsCopyable(true)
+              ->setIsLockable(false)
               ->setIsReorderable(false)
               ->setAliases(array('space', 'policy.space'))
               ->setTransactionType($type_space)
@@ -111,6 +112,7 @@ final class PhabricatorPolicyEditEngineExtension
               ->setValue($object->getSpacePHID());
             $fields[] = $space_field;
 
+            $space_field->setPolicyField($policy_field);
             $policy_field->setSpaceField($space_field);
           }
         }

src/applications/transactions/editfield/PhabricatorSpaceEditField.php

@@ -3,6 +3,17 @@
 final class PhabricatorSpaceEditField
   extends PhabricatorEditField {
 
+  private $policyField;
+
+  public function setPolicyField(PhabricatorPolicyEditField $policy_field) {
+    $this->policyField = $policy_field;
+    return $this;
+  }
+
+  public function getPolicyField() {
+    return $this->policyField;
+  }
+
   protected function newControl() {
     // NOTE: This field doesn't do anything on its own, it just serves as a
     // companion to the associated View Policy field.
@@ -17,4 +28,13 @@ final class PhabricatorSpaceEditField
     return new ConduitPHIDParameterType();
   }
 
+
+  public function shouldReadValueFromRequest() {
+    return $this->getPolicyField()->shouldReadValueFromRequest();
+  }
+
+  public function shouldReadValueFromSubmit() {
+    return $this->getPolicyField()->shouldReadValueFromSubmit();
+  }
+
 }