Document some understanding of MessageCache in RawAction/EditPage

[lhc/web/wiklou.git] / includes / actions / RawAction.php

diff --git a/includes/actions/RawAction.php b/includes/actions/RawAction.php
index 50eb28a..463019f 100644 (file)
--- a/includes/actions/RawAction.php
+++ b/includes/actions/RawAction.php
@@ -47,6 +47,9 @@ class RawAction extends FormlessAction {
                return false;
        }
 
+       /**
+        * @suppress SecurityCheck-XSS Non html mime type
+        */
        function onView() {
                $this->getOutput()->disable();
                $request = $this->getRequest();
@@ -160,13 +163,30 @@ class RawAction extends FormlessAction {
                $title = $this->getTitle();
                $request = $this->getRequest();
 
-               // If it's a MediaWiki message we can just hit the message cache
+               // If it's a page in the MediaWiki namespace, we can just hit the message cache
                if ( $request->getBool( 'usemsgcache' ) && $title->getNamespace() == NS_MEDIAWIKI ) {
-                       // The first "true" is to use the database, the second is to use
-                       // the content langue and the last one is to specify the message
-                       // key already contains the language in it ("/de", etc.).
-                       $text = MessageCache::singleton()->get( $title->getDBkey(), true, true, true );
-                       // If the message doesn't exist, return a blank
+                       // FIXME: The overhead and complexity of using MessageCache for serving
+                       // source code is not worth the marginal gain in performance. This should
+                       // instead use Revision::getRevisionText, which already has its own caching
+                       // layer, which is good enough fine given action=raw only responds with
+                       // a single page (no need for batch).
+                       //
+                       // Use of MessageCache:
+                       // - is unsustainable (T193271),
+                       // - can cause bugs due to "post-processing" (see MessageCache::get) not
+                       //   intending to apply to program source code,
+                       // - causes uncertaintly around whether or not localisation default
+                       //   placeholders are, can, and should be used, or not.
+                       $text = MessageCache::singleton()->get(
+                               $title->getDBkey(),
+                               // Yes, use the database.
+                               true,
+                               // Yes, use the content language.
+                               true,
+                               // Yes, the message key already contains the language in it ("/de", etc.)
+                               true
+                       );
+                       // If the local page doesn't exist, return a blank (not the default)
                        if ( $text === false ) {
                                $text = '';
                        }