Contrarily to what the docs say, Vim only stops completion if the value
returned by the omnifunc is -3 or -2. In other cases, if the value is negative
or greater than the current column, the start column is set to the current
column; otherwise, the value is used as the start column.
Vim internally moves the cursor to the start column before calling again the
omnifunc. Some omnifuncs like the one defined by the LanguageClient-neovim
plugin depend on this behavior to compute the list of candidates.
Allow users to still trigger Vim's omnifunc through C-Space when the
g:ycm_filetype_specific_completion_to_disable option is set for the current
filetype.
Now that the server supports Java natively, we need to use a
filetype that does not have native support to ensure that we call the
mocked omnifunc, but also one for which YCM has a semantic trigger.
Rather than picking another random languagse, which might break in the
future, we invent a language (ycmtest) and supply a manual trigger
mapping to the YouCompleteMe object.
