Parsoid: Stash: Honour our own ETag when retrieving the stash

Marko Obrovac · Marko Obrovac · commit 8cfead2be900 · 2019-10-16T05:49:46.000+02:00
If a client is switching between wikitext and HTML and in one of the two transforms they fail to provide the revision in the URI, trust that the ETag is correct and try to retrieve the stashed content using the information in the ETag. As a fall-back, though, try with the client-supplied revision as well. This is a port of #1208 to the proxy branch. Bug: T235465
diff --git a/lib/parsoid.js b/lib/parsoid.js
@@ -590,8 +590,24 @@ class ParsoidService {
             contentPromise = P.resolve(undefined);
         } else {
             if (etag && etag.suffix === 'stash' && from === 'html' && to === 'wikitext') {
+                // T235465: RB should trust its own ETag over the client-supplied revision, but
+                // allow for the client to be right, so provide their revision as a fall-back
+                const revMismatch = etag.rev !== rp.revision;
+                if (revMismatch) {
+                    // the ETag and URI parameter do not agree, log this (for now?)
+                    hyper.logger.log('warn/parsoid/etag_rev', {
+                        msg: 'The revisions in If-Match and URI differ'
+                    });
+                }
                 contentPromise = this._getStashedContent(hyper, rp.domain,
-                    rp.title, rp.revision, tid);
+                    rp.title, etag.rev, etag.tid)
+                .catch({ status: 404 }, (e) => {
+                    if (!revMismatch) {
+                        // the revisions match, so this is a genuine 404
+                        throw e;
+                    }
+                    return this._getStashedContent(hyper, rp.domain, rp.title, rp.revision, tid);
+                });
             } else {
                 contentPromise = this._getOriginalContent(hyper, req, rp.revision, tid);
             }
