Support rich diff rendering with DocumentEngine for added/removed files

Summary: Ref T13425. When a file (like a Jupyter notebook) is added or removed, we can still render a useful line-by-line diff.

Test Plan:
  - Viewed add/modify/remove of Jupyter, source code, and images in 2up/1up mode, everything looked okay.

Maniphest Tasks: T13425

Differential Revision: https://secure.phabricator.com/D20865

src/applications/differential/parser/DifferentialChangesetParser.php

@@ -1686,6 +1686,16 @@ final class DifferentialChangesetParser extends Phobject {
         break;
     }
 
+    $type_delete = DifferentialChangeType::TYPE_DELETE;
+    $type_add = DifferentialChangeType::TYPE_ADD;
+    $change_type = $changeset->getChangeType();
+
+    $no_old = ($change_type == $type_add);
+    $no_new = ($change_type == $type_delete);
+
+    if ($no_old) {
+      $old_ref = null;
+    } else {
       $old_ref = id(new PhabricatorDocumentRef())
         ->setName($changeset->getOldFile());
       if ($old_file) {
@@ -1697,7 +1707,11 @@ final class DifferentialChangesetParser extends Phobject {
 
         $old_ref->setData($old_data);
       }
+    }
 
+    if ($no_new) {
+      $new_ref = null;
+    } else {
       $new_ref = id(new PhabricatorDocumentRef())
         ->setName($changeset->getFilename());
       if ($new_file) {
@@ -1709,15 +1723,24 @@ final class DifferentialChangesetParser extends Phobject {
 
         $new_ref->setData($new_data);
       }
+    }
 
+
+    $old_engines = null;
+    if ($old_ref) {
       $old_engines = PhabricatorDocumentEngine::getEnginesForRef(
         $viewer,
         $old_ref);
+    }
 
+    $new_engines = null;
+    if ($new_ref) {
       $new_engines = PhabricatorDocumentEngine::getEnginesForRef(
         $viewer,
         $new_ref);
+    }
 
+    if ($new_engines !== null && $old_engines !== null) {
       $shared_engines = array_intersect_key($new_engines, $old_engines);
       $default_engine = head_key($new_engines);
 
@@ -1726,6 +1749,15 @@ final class DifferentialChangesetParser extends Phobject {
           unset($shared_engines[$key]);
         }
       }
+    } else if ($new_engines !== null) {
+      $shared_engines = $new_engines;
+      $default_engine = head_key($shared_engines);
+    } else if ($old_engines !== null) {
+      $shared_engines = $old_engines;
+      $default_engine = head_key($shared_engines);
+    } else {
+      return null;
+    }
 
     $engine_key = $this->getDocumentEngineKey();
     if (strlen($engine_key)) {

src/applications/differential/render/DifferentialChangesetOneUpRenderer.php

@@ -371,17 +371,27 @@ final class DifferentialChangesetOneUpRenderer
           $cell_classes = $block_diff->getNewClasses();
         }
       } else if ($row_type === 'old') {
+        if (!$old_ref) {
+          continue;
+        }
+
         $cell_content = $engine->newBlockContentView(
           $old_ref,
           $old);
+
         $cell_classes[] = 'old';
         $cell_classes[] = 'old-full';
 
         $new_key = null;
       } else if ($row_type === 'new') {
+        if (!$new_ref) {
+          continue;
+        }
+
         $cell_content = $engine->newBlockContentView(
           $new_ref,
           $new);
+
         $cell_classes[] = 'new';
         $cell_classes[] = 'new-full';
 

src/applications/files/diff/PhabricatorDocumentEngineBlocks.php

@@ -15,7 +15,10 @@ final class PhabricatorDocumentEngineBlocks
     return $this->messages;
   }
 
-  public function addBlockList(PhabricatorDocumentRef $ref, array $blocks) {
+  public function addBlockList(
+    PhabricatorDocumentRef $ref = null,
+    array $blocks = array()) {
+
     assert_instances_of($blocks, 'PhabricatorDocumentEngineBlock');
 
     $this->lists[] = array(

src/applications/files/document/PhabricatorDocumentEngine.php

@@ -32,8 +32,8 @@ abstract class PhabricatorDocumentEngine
   }
 
   public function canDiffDocuments(
-    PhabricatorDocumentRef $uref,
-    PhabricatorDocumentRef $vref) {
+    PhabricatorDocumentRef $uref = null,
+    PhabricatorDocumentRef $vref = null) {
     return false;
   }
 

src/applications/files/document/PhabricatorImageDocumentEngine.php

@@ -18,21 +18,38 @@ final class PhabricatorImageDocumentEngine
   }
 
   public function canDiffDocuments(
-    PhabricatorDocumentRef $uref,
-    PhabricatorDocumentRef $vref) {
+    PhabricatorDocumentRef $uref = null,
+    PhabricatorDocumentRef $vref = null) {
 
-    // For now, we can only render a rich image diff if both documents have
+    // For now, we can only render a rich image diff if the documents have
     // their data stored in Files already.
 
-    return ($uref->getFile() && $vref->getFile());
+    if ($uref && !$uref->getFile()) {
+      return false;
+    }
+
+    if ($vref && !$vref->getFile()) {
+      return false;
+    }
+
+    return true;
   }
 
   public function newEngineBlocks(
-    PhabricatorDocumentRef $uref,
-    PhabricatorDocumentRef $vref) {
+    PhabricatorDocumentRef $uref = null,
+    PhabricatorDocumentRef $vref = null) {
 
+    if ($uref) {
       $u_blocks = $this->newDiffBlocks($uref);
+    } else {
+      $u_blocks = array();
+    }
+
+    if ($vref) {
       $v_blocks = $this->newDiffBlocks($vref);
+    } else {
+      $v_blocks = array();
+    }
 
     return id(new PhabricatorDocumentEngineBlocks())
       ->addBlockList($uref, $u_blocks)

src/applications/files/document/PhabricatorJupyterDocumentEngine.php

@@ -36,20 +36,29 @@ final class PhabricatorJupyterDocumentEngine
   }
 
   public function canDiffDocuments(
-    PhabricatorDocumentRef $uref,
-    PhabricatorDocumentRef $vref) {
+    PhabricatorDocumentRef $uref = null,
+    PhabricatorDocumentRef $vref = null) {
     return true;
   }
 
   public function newEngineBlocks(
-    PhabricatorDocumentRef $uref,
-    PhabricatorDocumentRef $vref) {
+    PhabricatorDocumentRef $uref = null,
+    PhabricatorDocumentRef $vref = null) {
 
     $blocks = new PhabricatorDocumentEngineBlocks();
 
     try {
+      if ($uref) {
         $u_blocks = $this->newDiffBlocks($uref);
+      } else {
+        $u_blocks = array();
+      }
+
+      if ($vref) {
         $v_blocks = $this->newDiffBlocks($vref);
+      } else {
+        $v_blocks = array();
+      }
 
       $blocks->addBlockList($uref, $u_blocks);
       $blocks->addBlockList($vref, $v_blocks);