Broken Blog Post Filtering in SharePoint 2013

Some time last spring I created two blog sites to a customer SharePoint 2013 intranet. I set them up quite similarily, the only difference being that I added some custom fields to the other one. This should, in my logic, not affect anything in the different blog views - such as archives and category views - since I didn't touch any of the OOB fields. Whatever the reason, the end result was however, that last week the customer noticed (hmm, not very active blogging then ;) ) that on the other blog site the category and archive pages were broken. They did not filter the posts anymore as they should.

I banged my head against the wall for a while, googled, googled some more and tried this and that. Nothing seemed to help. One workaround I tried was this most commonly mentioned solution of adding a URL filter web part and setting it up as instructed eg. in this post here.

This, however, did not work for me, or this customer site. Be it due to the language pack (Finnish site) or something else, but it did not work. So I needed something else. This is what I did:

1) I created a new blog in the test environment. Really it doesn't matter where, just as long as you can access it in SharePoint Designer.

2) I opened both the new non-broken blog site and the old broken one in SharePoint Designer. I know. I sighed deep when I realized I really needed to go that far. But unfortunately the problem seems to reside in the corrupted query of the posts web part and in order to fix that, yes, SPD is required.

3) The two pages that are not working properly when categories and archive are not filtering posts, are Categories.aspx and Date.aspx. These are not in the Site Pages library of the blog site; you need to dig them out from the All files directory. 

All files > Lists > Categories > Category.aspx

All files > Lists > Posts > Date.aspx

Open both files on both your broken site and the new one created.

4) No, copying all code from one to the other will not work because of the GUIDs. As stated earlier, the broken part is the CAML query of the Posts web part. So the first thing to do is to locate the Posts web part. Since you are working in code view only, look for the main place holder with the blog-MainArea to find the correct web part.

5) Focus on the line starting <View Name="{...

6) Scroll horizontally (or set your page to wrap lines) until you find the <query> tag. This begins the CAML query for the web part. On the borken page it was missing parts. So I copied the query (everything between the <query> and </query> tags) from my new site category and date pages to the broken corresponding ones, replacing the broken queries.

7) I saved my files and tested them. The initial refresh filtered posts nicely, but the blog navigation (the categories list and the blog archive) links were broken, for the Blog tools web part was broken. It seems that any time you open a blog page into SharePoint Designer, this web part breaks.

8) So, I edited both pages in the browser, deleting the broken Blog tools part and adding it back in place and yes, things started functioning again! 

Hope this helps someone else save some time. Boy, there's never a boring day with SharePoint!