From dbdfac1e072ef7d77513bf41cac2ee1a7d8678f3 Mon Sep 17 00:00:00 2001
From: epriestley <git@epriestley.com>
Date: Wed, 5 Aug 2020 12:56:04 -0700
Subject: [PATCH] Recover inline comments which are "adjusted" off the end of a
 diff

Summary:
See PHI1834. Currently, the inline adjustment engine can sometime "adjust" an inline off the end of a diff. If it does, we lay it out on an invalid display line here and never render it.

Instead, make sure that layout never puts a comment on an invalid line, so the UI is robust against questionable decisions by the adjustment engine: no adjustment should be able to accidentally discard an inline.

Test Plan:
  - Created a two diff revision, where Diffs 1 and 2 have "alphabet.txt" with A-Z on one line each. The file is unchanged across diffs; some other file is changed.
  - Added a comment to lines P-Z of Diff 1.
  - Before: comment is adjusted out of range on Diff 2 and not shown in the UI.
  - After: comment is still adjusted out of range internally, but now corrected into the display range and shown.

Differential Revision: https://secure.phabricator.com/D21435
---
 .../parser/DifferentialChangesetParser.php    | 26 +++++++++++++++----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/applications/differential/parser/DifferentialChangesetParser.php b/src/applications/differential/parser/DifferentialChangesetParser.php
index 3652d18a9a..ad62b2a1ef 100644
--- a/src/applications/differential/parser/DifferentialChangesetParser.php
+++ b/src/applications/differential/parser/DifferentialChangesetParser.php
@@ -1053,14 +1053,30 @@ final class DifferentialChangesetParser extends Phobject {
       $this->comments = id(new PHUIDiffInlineThreader())
         ->reorderAndThreadCommments($this->comments);
 
+      $old_max_display = 1;
+      foreach ($this->old as $old) {
+        if (isset($old['line'])) {
+          $old_max_display = $old['line'];
+        }
+      }
+
+      $new_max_display = 1;
+      foreach ($this->new as $new) {
+        if (isset($new['line'])) {
+          $new_max_display = $new['line'];
+        }
+      }
+
       foreach ($this->comments as $comment) {
-        $final = $comment->getLineNumber() +
-          $comment->getLineLength();
-        $final = max(1, $final);
+        $display_line = $comment->getLineNumber() + $comment->getLineLength();
+        $display_line = max(1, $display_line);
+
         if ($this->isCommentOnRightSideWhenDisplayed($comment)) {
-          $new_comments[$final][] = $comment;
+          $display_line = min($new_max_display, $display_line);
+          $new_comments[$display_line][] = $comment;
         } else {
-          $old_comments[$final][] = $comment;
+          $display_line = min($old_max_display, $display_line);
+          $old_comments[$display_line][] = $comment;
         }
       }
     }