When creating a new tag-wiki, I have encountered a somewhat unusual error message saying: "An error occurred submitting the post."
I have seen some older posts with similar error messages: Tag-wiki edit submit gets error, clearer reasons requested, Wiki-tag edit error is non-descriptive (and the posts linked there). Unless I missed something, in those cases the comments/answers say that this was caused by full suggested edit review. However, this is different - I did not make a suggested edit, it was on a site where I can directly edit tag-wikis. Moreover, the suggested edits review queue both on meta and on the main site seem to be empty.
Steps to reproduce
I will write exactly what I did. I am not sure whether all these steps are essential. (However, these steps lead to the error on two different tag-infos, so at least to some extent this should be reproducible.)
- I had an empty tag-info on a per-site-meta. (Although it is probably not that relevant that it was on meta.)
- I clicked on edit. I put the tag-excerpt. (In my case I copied it from the corresponding tag-info on Meta Stack Exchange.) I saved the edit.
- Then I clicked on edit again. I filled in (copied) the body of the tag-info. And I have also included an edit summary. (Which was: "Basic tag-info copied from https://meta.stackexchange.com/tags/keyboard-shortcuts/info")
After this I got an error message.
Let me also explain why I separated the steps 2 and 3 rather than doing both at the same time. I wanted to create at first the initial version of tag-info, by copying from Meta Stack Exchange. (With the plan to work then on expanding it a bit more.) I wanted to do it in such way that the revision history clearly says that the initial version was copied from here. Since in the initial edit I did not have any field where to put the edit summary, I edited only the tag-excerpt and I wanted to include the edit summary in the subsequent edit, where also the tag-wiki was copied.
I did this as a test - shortly after I got the same error message on another tag-info, but I was able to edit that tag-info when I tried a few minutes later.
In the developer tools in Google Chrome I saw the "Oops! Something Bad Happened" error page in the Response tab. I have copied the content of that tab here: https://pastebin.com/uAhhZYhQ. Below is a screenshot of the Preview tab. (I am not very experienced with these tools, so I wasn't really sure what I should look for.)
P.S. I should thank Glorfindel for his time and advice when I asked about this in chat.