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Code Issues Releases Wiki Activity

putSaver: detect edit conflicts to prevent clobbering, if possible

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if the server supplies an ETag, we send it back when saving, allowing
the server to detect edit conflicts and respond with 412 (cf.
https://www.w3.org/1999/04/Editing/)

caveats:
* this only kicks in after the first save, as we don't have access to
  the ETag when first loading the document
* there's no recovery mechanism (e.g. resetting `this.etag` in order to
  force clobbering), other than manually reloading the document
This commit is contained in:
FND 2016-10-15 17:03:50 +02:00
parent d7b6917638
commit 2d75cb83af
1 changed files with 8 additions and 2 deletions
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10
core/modules/savers/put.js
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@ -27,7 +27,7 @@ var PutSaver = function(wiki) {
req.open("OPTIONS",encodeURI(document.location.protocol + "//" + document.location.hostname + ":" + document.location.port + document.location.pathname)); req.open("OPTIONS",encodeURI(document.location.protocol + "//" + document.location.hostname + ":" + document.location.port + document.location.pathname));
req.onload = function() { req.onload = function() {
// Check DAV header http://www.webdav.org/specs/rfc2518.html#rfc.section.9.1 // Check DAV header http://www.webdav.org/specs/rfc2518.html#rfc.section.9.1
self.serverAcceptsPuts = (this.status === 200 && !!this.getResponseHeader('dav')); self.serverAcceptsPuts = (this.status === 200 && !!this.getResponseHeader("dav"));
}; };
req.send(); req.send();
}; };
@ -37,19 +37,25 @@ PutSaver.prototype.save = function(text,method,callback) {
return false; return false;
} }
var req = new XMLHttpRequest(); var req = new XMLHttpRequest();
// TODO: store/check ETags if supported by server, to protect against overwrites // TODO: in case of edit conflict
// Prompt: Do you want to save over this? Y/N // Prompt: Do you want to save over this? Y/N
// Merging would be ideal, and may be possible using future generic merge flow // Merging would be ideal, and may be possible using future generic merge flow
req.onload = function() { req.onload = function() {
if (this.status === 200 || this.status === 201) { if (this.status === 200 || this.status === 201) {
this.etag = this.getResponseHeader("ETag");
callback(null); // success callback(null); // success
} }
else if (this.status === 412) { // edit conflict
callback("File changed on server");
else { else {
callback(this.responseText); // fail callback(this.responseText); // fail
} }
}; };
req.open("PUT", encodeURI(window.location.href)); req.open("PUT", encodeURI(window.location.href));
req.setRequestHeader("Content-Type", "text/html;charset=UTF-8"); req.setRequestHeader("Content-Type", "text/html;charset=UTF-8");
if (this.etag) {
req.setRequestHeader("If-Match", this.etag);
}
req.send(text); req.send(text);
return true; return true;
}; };