DifferenceEngine: Autodetect if wikidiff2 is installed

If wikidiff2 is installed, use it for diffing without requiring
$wgExternalDiffEngine to be set to 'wikidiff2'.

Also add some extra sanity-checking by coercing all non-string values to
false and make sure the custom diff executable passes `is_executable()`.

Change-Id: I32b670ebf613be9f1c034d65d006829a215614da

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 6d08eec..f2e2420 100644 (file)
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -8059,10 +8059,9 @@ $wgUpdateRowsPerQuery = 100;
 
 /**
  * Name of the external diff engine to use. Supported values:
- * * false: default PHP implementation
- * * 'wikidiff2': Wikimedia's fast difference engine implemented as a PHP/HHVM module
- * * 'wikidiff' and 'wikidiff3' are treated as false for backwards compatibility
- * * any other string is treated as a path to external diff executable
+ * * string: path to an external diff executable
+ * * false: wikidiff2 PHP/HHVM module if installed, otherwise the default PHP implementation
+ * * 'wikidiff', 'wikidiff2', and 'wikidiff3' are treated as false for backwards compatibility
  */
 $wgExternalDiffEngine = false;
 

diff --git a/includes/diff/DifferenceEngine.php b/includes/diff/DifferenceEngine.php
index c5e94c5..7471b78 100644 (file)
--- a/includes/diff/DifferenceEngine.php
+++ b/includes/diff/DifferenceEngine.php
@@ -923,18 +923,23 @@ class DifferenceEngine extends ContextSource {
                if ( $wgExternalDiffEngine == 'wikidiff' || $wgExternalDiffEngine == 'wikidiff3' ) {
                        wfDeprecated( "\$wgExternalDiffEngine = '{$wgExternalDiffEngine}'", '1.27' );
                        $wgExternalDiffEngine = false;
+               } elseif ( $wgExternalDiffEngine == 'wikidiff2' ) {
+                       // Same as above, but with no deprecation warnings
+                       $wgExternalDiffEngine = false;
+               } elseif ( !is_string( $wgExternalDiffEngine ) ) {
+                       // And prevent people from shooting themselves in the foot...
+                       wfWarn( '$wgExternalDiffEngine is set to a non-string value, forcing it to false' );
+                       $wgExternalDiffEngine = false;
                }
 
-               if ( $wgExternalDiffEngine == 'wikidiff2' ) {
-                       if ( function_exists( 'wikidiff2_do_diff' ) ) {
-                               # Better external diff engine, the 2 may some day be dropped
-                               # This one does the escaping and segmenting itself
-                               $text = wikidiff2_do_diff( $otext, $ntext, 2 );
-                               $text .= $this->debug( 'wikidiff2' );
+               if ( function_exists( 'wikidiff2_do_diff' ) && $wgExternalDiffEngine === false ) {
+                       # Better external diff engine, the 2 may some day be dropped
+                       # This one does the escaping and segmenting itself
+                       $text = wikidiff2_do_diff( $otext, $ntext, 2 );
+                       $text .= $this->debug( 'wikidiff2' );
 
-                               return $text;
-                       }
-               } elseif ( $wgExternalDiffEngine !== false ) {
+                       return $text;
+               } elseif ( $wgExternalDiffEngine !== false && is_executable( $wgExternalDiffEngine ) ) {
                        # Diff via the shell
                        $tmpDir = wfTempDir();
                        $tempName1 = tempnam( $tmpDir, 'diff_' );