Improve handle loading semantics for tokenizers

Summary:
Ref T7689. Fixes T7688. When there are a bunch of tokenizers with different values of the same object type (e.g. 5 tokenizers with users a, b, c, d, e) we currently issue 5 separate queries to load their handles.

Improve this behavior in the common case so we can usually batch these loads.

Test Plan:
  - In Maniphest, set the various search fields to different values.
  - Used DarkConsole to examine query plan.
  - Saw fewer queries after patch than before.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7688, T7689

Differential Revision: https://secure.phabricator.com/D12261

src/view/AphrontTagView.php

@@ -89,10 +89,6 @@ abstract class AphrontTagView extends AphrontView {
     return $this->renderChildren();
   }
 
-  protected function willRender() {
-    return;
-  }
-
   final public function render() {
     $this->willRender();
 

src/view/AphrontView.php

@@ -149,6 +149,22 @@ abstract class AphrontView extends Phobject
 /* -(  Rendering  )---------------------------------------------------------- */
 
 
+  /**
+   * Inconsistent, unreliable pre-rendering hook.
+   *
+   * This hook //may// fire before views render. It is not fired reliably, and
+   * may fire multiple times.
+   *
+   * If it does fire, views might use it to register data for later loads, but
+   * almost no datasources support this now; this is currently only useful for
+   * tokenizers. This mechanism might eventually see wider support or might be
+   * removed.
+   */
+  public function willRender() {
+    return;
+  }
+
+
   abstract public function render();
 
 

src/view/form/AphrontFormView.php

@@ -94,6 +94,7 @@ final class AphrontFormView extends AphrontView {
   public function buildLayoutView() {
     foreach ($this->controls as $control) {
       $control->setUser($this->getUser());
+      $control->willRender();
     }
 
     return id(new PHUIFormLayoutView())

src/view/form/control/AphrontFormTokenizerControl.php

@@ -6,6 +6,7 @@ final class AphrontFormTokenizerControl extends AphrontFormControl {
   private $disableBehavior;
   private $limit;
   private $placeholder;
+  private $handles;
 
   public function setDatasource(PhabricatorTypeaheadDatasource $datasource) {
     $this->datasource = $datasource;
@@ -31,41 +32,17 @@ final class AphrontFormTokenizerControl extends AphrontFormControl {
     return $this;
   }
 
+  public function willRender() {
+    // Load the handles now so we'll get a bulk load later on when we actually
+    // render them.
+    $this->loadHandles();
+  }
+
   protected function renderInput() {
     $name = $this->getName();
-    $values = nonempty($this->getValue(), array());
 
-    // Values may either be handles (which are now legacy/deprecated) or
-    // strings. Load handles for any PHIDs.
-    $load = array();
-    $handles = array();
-    $select = array();
-    foreach ($values as $value) {
-      if ($value instanceof PhabricatorObjectHandle) {
-        $handles[$value->getPHID()] = $value;
-        $select[] = $value->getPHID();
-      } else {
-        $load[] = $value;
-        $select[] = $value;
-      }
-    }
-
-    // TODO: Once this code path simplifies, move this prefetch to setValue()
-    // so we can bulk load across multiple controls.
-
-    if ($load) {
-      $viewer = $this->getUser();
-      if (!$viewer) {
-        // TODO: Clean this up when handles go away.
-        throw new Exception(
-          pht('Call setUser() before rendering tokenizer string values.'));
-      }
-      $loaded_handles = $viewer->loadHandles($load);
-      $handles = $handles + iterator_to_array($loaded_handles);
-    }
-
-    // Reorder the list into input order.
-    $handles = array_select_keys($handles, $select);
+    $handles = $this->loadHandles();
+    $handles = iterator_to_array($handles);
 
     if ($this->getID()) {
       $id = $this->getID();
@@ -112,4 +89,21 @@ final class AphrontFormTokenizerControl extends AphrontFormControl {
     return $template->render();
   }
 
+  private function loadHandles() {
+    if ($this->handles === null) {
+      $viewer = $this->getUser();
+      if (!$viewer) {
+        throw new Exception(
+          pht(
+            'Call setUser() before rendering tokenizers. Use appendControl() '.
+            'on AphrontFormView to do this easily.'));
+      }
+
+      $values = nonempty($this->getValue(), array());
+      $this->handles = $viewer->loadHandles($values);
+    }
+
+    return $this->handles;
+  }
+
 }

src/view/phui/PHUIListView.php

@@ -152,7 +152,7 @@ final class PHUIListView extends AphrontTagView {
     return $this->items;
   }
 
-  protected function willRender() {
+  public function willRender() {
     $key_map = array();
     foreach ($this->items as $item) {
       $key = $item->getKey();