We simply apply the changes to each file in turn. The existing replacement
logic is unchanged, except that it now no longer implicitly assumes we are
talking about the current buffer.
If a buffer is not visible for the requested file name, we open it in
a horizontal split, make the edits, then hide the window. Because this
can cause UI flickering, and leave hidden, modified buffers around, we
issue a warning to the user stating the number of files for which we are
going to do this. We pop up the quickfix list at the end of applying
the edits to allow the user to see what we changed.
If the user opts to abort due to, say, the file being open in another
window, we simply raise an error and give up, as undoing the changes
is too complex to do programatically, but trivial to do manually in such
a rare case.
Vim's QuickFix lists require 1-based columns, which is what is returned
from ycmd's commands.
As noted in the comments, the Vim documentation for setqflist is
somewhat vague about this "byte offset", but it is confirmed to mean
"1-based column number" both in testing and in :help getqflist.
We display the detailed info text in the preview window. Vim's preview window is
designed to display actual files, not scratch data. Our approach is to open a
temporary file, even though that file is never written. This way, all of Vim's
existing settings for the preview window (and people's configured mappings) just
work. This is also consistent with showing the documentation in the preview
window during completion.
Other plugins have more complicated functions for this (such as eclim), or
Scratch.vim, but this approach is simple and doesn't require external
dependencies or additional settings.
Tests:
This required fixing a sort-of-bug in which the mock'd Vim module was always
only set once, and could not be changed outside of the module which created it.
This meant that it wasn't easy to have arbitrary tests, because it was dependent
on the order in which the tests execute as to whether the return from
MockVimModule() was actually the one in use.
The solution was to make the mock'd vim module a singleton, and use mock's
patch decorator to assign new MagicMock() instances to those methods in the vim
module which a particular test is interested in.
