Prepare a replacement for Controller->renderHandlesForPHIDs()

Summary:
Ref T7689. This gives HandleLists `renderList()` and `renderHandle()` methods, which return views that can perform just-in-time data fetching and generally look and feel like other rendering code, instead of being odd pseudo-functional methods on `Controller`.

Also converts callsites on the Maniphest detail page to use these methods.

Next changes will wipe out more of the callsites.

Test Plan:
  - Viewed Maniphest detail page with many relevant handles.
  - Created a new subtask.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7689

Differential Revision: https://secure.phabricator.com/D12205

src/__phutil_library_map__.php

@@ -1165,7 +1165,9 @@ phutil_register_library_map(array(
     'PHUIFormLayoutView' => 'view/form/PHUIFormLayoutView.php',
     'PHUIFormMultiSubmitControl' => 'view/form/control/PHUIFormMultiSubmitControl.php',
     'PHUIFormPageView' => 'view/form/PHUIFormPageView.php',
+    'PHUIHandleListView' => 'applications/phid/view/PHUIHandleListView.php',
     'PHUIHandleTagListView' => 'applications/phid/view/PHUIHandleTagListView.php',
+    'PHUIHandleView' => 'applications/phid/view/PHUIHandleView.php',
     'PHUIHeaderView' => 'view/phui/PHUIHeaderView.php',
     'PHUIIconExample' => 'applications/uiexample/examples/PHUIIconExample.php',
     'PHUIIconView' => 'view/phui/PHUIIconView.php',
@@ -4423,7 +4425,9 @@ phutil_register_library_map(array(
     'PHUIFormLayoutView' => 'AphrontView',
     'PHUIFormMultiSubmitControl' => 'AphrontFormControl',
     'PHUIFormPageView' => 'AphrontView',
+    'PHUIHandleListView' => 'AphrontTagView',
     'PHUIHandleTagListView' => 'AphrontTagView',
+    'PHUIHandleView' => 'AphrontView',
     'PHUIHeaderView' => 'AphrontView',
     'PHUIIconExample' => 'PhabricatorUIExample',
     'PHUIIconView' => 'AphrontTagView',

src/applications/maniphest/controller/ManiphestTaskDetailController.php

@@ -85,10 +85,6 @@ final class ManiphestTaskDetailController extends ManiphestController {
     $phids = array_keys($phids);
     $handles = $user->loadHandles($phids);
 
-    // TODO: This is double-loading because we have a separate call to
-    // renderHandlesForPHIDs(). Clean this up in the next pass.
-    $this->loadHandles($phids);
-
     $info_view = null;
     if ($parent_task) {
       $info_view = new PHUIInfoView();
@@ -100,8 +96,8 @@ final class ManiphestTaskDetailController extends ManiphestController {
           ->setText(pht('Create Another Subtask')));
 
       $info_view->appendChild(hsprintf(
-        'Created a subtask of <strong>%s</strong>',
-        $handles[$parent_task->getPHID()]->renderLink()));
+        'Created a subtask of <strong>%s</strong>.',
+        $handles->renderHandle($parent_task->getPHID())));
     } else if ($workflow == 'create') {
       $info_view = new PHUIInfoView();
       $info_view->setSeverity(PHUIInfoView::SEVERITY_NOTICE);
@@ -457,7 +453,7 @@ final class ManiphestTaskDetailController extends ManiphestController {
     $view->addProperty(
       pht('Assigned To'),
       $task->getOwnerPHID()
-        ? $handles[$task->getOwnerPHID()]->renderLink()
+        ? $handles->renderHandle($task->getOwnerPHID())
         : phutil_tag('em', array(), pht('None')));
 
     $view->addProperty(
@@ -466,7 +462,7 @@ final class ManiphestTaskDetailController extends ManiphestController {
 
     $view->addProperty(
       pht('Author'),
-      $handles[$task->getAuthorPHID()]->renderLink());
+      $handles->renderHandle($task->getAuthorPHID()));
 
     $source = $task->getOriginalEmailSource();
     if ($source) {
@@ -504,7 +500,7 @@ final class ManiphestTaskDetailController extends ManiphestController {
         ->execute();
 
       foreach ($commit_phids as $phid) {
-        $revisions_commits[$phid] = $handles[$phid]->renderLink();
+        $revisions_commits[$phid] = $handles->renderHandle($phid);
         $revision_phid = key($drev_edges[$phid][$commit_drev]);
         $revision_handle = $handles->getHandleIfExists($revision_phid);
         if ($revision_handle) {
@@ -520,9 +516,10 @@ final class ManiphestTaskDetailController extends ManiphestController {
 
     foreach ($edge_types as $edge_type => $edge_name) {
       if ($edges[$edge_type]) {
+        $edge_handles = $viewer->loadHandles(array_keys($edges[$edge_type]));
         $view->addProperty(
           $edge_name,
-          $this->renderHandlesForPHIDs(array_keys($edges[$edge_type])));
+          $edge_handles->renderList());
       }
     }
 

src/applications/phid/handle/pool/PhabricatorHandleList.php

@@ -26,6 +26,7 @@ final class PhabricatorHandleList
   private $phids;
   private $handles;
   private $cursor;
+  private $map;
 
   public function setHandlePool(PhabricatorHandlePool $pool) {
     $this->handlePool = $pool;
@@ -71,6 +72,33 @@ final class PhabricatorHandleList
   }
 
 
+/* -(  Rendering  )---------------------------------------------------------- */
+
+
+  /**
+   * Return a @{class:PHUIHandleListView} which can render the handles in
+   * this list.
+   */
+  public function renderList() {
+    return id(new PHUIHandleListView())
+      ->setHandleList($this);
+  }
+
+
+  /**
+   * Return a @{class:PHUIHandleView} which can render a specific handle.
+   */
+  public function renderHandle($phid) {
+    if (!isset($this[$phid])) {
+      throw new Exception(
+        pht('Trying to render a handle which does not exist!'));
+    }
+
+    return id(new PHUIHandleView())
+      ->setHandleList($this)
+      ->setHandlePHID($phid);
+  }
+
 /* -(  Iterator  )----------------------------------------------------------- */
 
 
@@ -99,10 +127,15 @@ final class PhabricatorHandleList
 
 
   public function offsetExists($offset) {
-    if ($this->handles === null) {
-      $this->loadHandles();
+    // NOTE: We're intentionally not loading handles here so that isset()
+    // checks do not trigger fetches. This gives us better bulk loading
+    // behavior, particularly when invoked through methods like renderHandle().
+
+    if ($this->map === null) {
+      $this->map = array_fill_keys($this->phids, true);
     }
-    return isset($this->handles[$offset]);
+
+    return isset($this->map[$offset]);
   }
 
   public function offsetGet($offset) {

src/applications/phid/view/PHUIHandleListView.php

@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * Convenience class for rendering a list of handles.
+ *
+ * This class simplifies rendering a list of handles and improves loading and
+ * caching semantics in the rendering pipeline by delaying bulk loads until the
+ * last possible moment.
+ */
+final class PHUIHandleListView
+  extends AphrontTagView {
+
+  private $handleList;
+  private $inline;
+
+  public function setHandleList(PhabricatorHandleList $list) {
+    $this->handleList = $list;
+    return $this;
+  }
+
+  public function setInline($inline) {
+    $this->inline = $inline;
+    return $this;
+  }
+
+  public function getInline() {
+    return $this->inline;
+  }
+
+  protected function getTagName() {
+    // TODO: It would be nice to render this with a proper <ul />, at least in
+    // block mode, but don't stir the waters up too much for now.
+    return 'span';
+  }
+
+  protected function getTagContent() {
+    $items = array();
+    foreach ($this->handleList as $handle) {
+      $items[] = $handle->renderLink();
+    }
+
+    if ($this->getInline()) {
+      $items = phutil_implode_html(', ', $items);
+    } else {
+      $items = phutil_implode_html(phutil_tag('br'), $items);
+    }
+
+    return $items;
+  }
+
+}

src/applications/phid/view/PHUIHandleView.php

@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * Convenience class for rendering a single handle.
+ *
+ * This class simplifies rendering a single handle, and improves loading and
+ * caching semantics in the rendering pipeline by loading data at the last
+ * moment.
+ */
+
+final class PHUIHandleView
+  extends AphrontView {
+
+  private $handleList;
+  private $handlePHID;
+
+  public function setHandleList(PhabricatorHandleList $list) {
+    $this->handleList = $list;
+    return $this;
+  }
+
+  public function setHandlePHID($phid) {
+    $this->handlePHID = $phid;
+    return $this;
+  }
+
+  public function render() {
+    return $this->handleList[$this->handlePHID]->renderLink();
+  }
+
+}