Pass a real context object to Phriction previews, fixing mentions

Summary:
Fixes T13662. Phriction currently passes a map as a "context object", but this code is ancient and predates the modern meaning of a "context object". In modern code, context objects should be real objects.

Provide a real object as a context object. We do this by either loading the actual document or constructing a synthetic version of it.

Test Plan:
  - Edited an existing document, observing the preview:
    - Used a mention rule, saw a preview.
    - Used `[[ a ]]` and `[[ ./a ]]` absolute and relative reference rules, saw accurate previews.
  - Edited a new document, observing the preview:
    - Used a mention rule, saw a preview.
    - Used absolute/relative references, saw accurate previews.
  - Grepped for other references to the removed properties (`phriction.isPreview` and `phriction.slug`), found none remaining.

Reviewers: 0

Reviewed By: 0

Maniphest Tasks: T13662

Differential Revision: https://secure.phabricator.com/D21709

src/applications/phriction/controller/PhrictionMarkupPreviewController.php

@@ -3,13 +3,30 @@
 final class PhrictionMarkupPreviewController
   extends PhabricatorController {
 
-  public function processRequest() {
-    $request = $this->getRequest();
-    $viewer = $request->getUser();
+  public function handleRequest(AphrontRequest $request) {
+    $viewer = $request->getViewer();
 
     $text = $request->getStr('text');
     $slug = $request->getStr('slug');
 
+    $document = id(new PhrictionDocumentQuery())
+      ->setViewer($viewer)
+      ->withSlugs(array($slug))
+      ->needContent(true)
+      ->executeOne();
+    if (!$document) {
+      $document = PhrictionDocument::initializeNewDocument(
+        $viewer,
+        $slug);
+
+      $content = id(new PhrictionContent())
+        ->setSlug($slug);
+
+      $document
+        ->setPHID($document->generatePHID())
+        ->attachContent($content);
+    }
+
     $output = PhabricatorMarkupEngine::renderOneObject(
       id(new PhabricatorMarkupOneOff())
         ->setPreserveLinebreaks(true)
@@ -17,10 +34,7 @@ final class PhrictionMarkupPreviewController
         ->setContent($text),
       'default',
       $viewer,
-      array(
-        'phriction.isPreview' => true,
-        'phriction.slug' => $slug,
-      ));
+      $document);
 
     return id(new AphrontAjaxResponse())
       ->setContent($output);

src/applications/phriction/markup/PhrictionRemarkupRule.php

@@ -273,13 +273,6 @@ final class PhrictionRemarkupRule extends PhutilRemarkupRule {
       return null;
     }
 
-    // Handle content when it's a preview for the Phriction editor.
-    if (is_array($context)) {
-      if (idx($context, 'phriction.isPreview')) {
-        return idx($context, 'phriction.slug');
-      }
-    }
-
     if ($context instanceof PhrictionContent) {
       return $context->getSlug();
     }