Emacs 26 xref window management broke code1

[wyuenho]

Steps to reproduce

1. Install Emacs 26.1 (I've tested on the NS and the Mituharu Mac port)
2. Call (purpose-x-code1-setup) in .emacs
3. Visit an ELISP file that has a symbol that will pop up an xref buffer for selection after (xref-find-definitions) (I visited company.el)
4. Adjust the edit window's width to something "small enough" (the screen cap edit window has a 93 (window-total-width)
5. Move point to the symbol (I moved to company-backends)
6. Press M-.
7. The window showing the xref buffer is covered with an extra dired buffer
8. Press q exits the dired buffer
9. Press q again to exit the xref buffer
10. Now we are back to the dired buffer we just quit and buried.
11. Press q twice to exit the dired buffer
12. Now there are 2 windows showing the file we visited.

Expected behavior

The extra dired window should never show up to begin with.

I've git-bisected this issue to be caused by this commit to Emacs 26, all subsequent commits shows the same behavior.

I'm not exactly sure what's going on here, does this have something to do with some weird interaction with #98 ?

P.S. I have pop-up-frames set to nil.

[bmag]

Couldn't reproduce it locally with, but did encounter some weirdness when using code1 while purpose-mode is disabled (which I think is to be expected).

Your repro steps don't mention if purpose-mode is enabled or not. Does this bug happen with or without purpsoe-mode?

[wyuenho]

I have purpose-mode enabled.

[wyuenho]

I was able to reproduce this with open -a emacs --args -Q and just window-purpose and company installed. I then M-x purpose-mode and followed up with M-x company-mode to warm up xref, and then tried M-. on one of the backend symbols on company-backends again.

[bmag]

I think I found the bug, will fix tomorrow or the day after.

[bmag]

Should be fixed by a393b85

[wyuenho]

This fix made things much worst. Now a dired buffer will pop open and take over the edit buffer whenever I visit a file. The post-command-hook that updates the dired buffer also put it onto the edit buffer after every command

[bmag]

Reverted for now.

[wyuenho]

Actually my mistake, the buffer does display at the correct window with this fix and the xref problem is gone, but hide-details mode did not take effect because that mode is buffer-local you have to wrap it in a with-current-buffer. I'll submit a fix now.

[bmag]

Ah, ok. Merged the fix, thanks.