It is possible for a given backend’s implementation to use
flymake-make-diagnostic to create diagnostics for buffers or
files other than the “source” buffer where Flymake was enabled. For
instance, this is useful when a given backend has access to
information about the health of neighboring files that are not yet
visited or whose diagnostics depend on the current buffer’s state.
There are two alternative ways to go about doing this:
.cfile also reports a number of associated problems in an neighboring
.hfile, it is better to create so-called “foreign” diagnostics.
This is done by passing a file name to
(see Flymake utility functions). Then, the resulting object is
simply reported along with the other “domestic” diagnostics for the
source buffer (see Backend functions). When the neighboring file
is visited as a buffer and Flymake is active there, a number of
supplemental annotations will appear and automatically update whenever
as the “source” buffer is syntax-checked.
Flymake will look up this variable when asked to compile project-wide lists of diagnostics. The backend should add one or more alist entries that look like (file-name . diags). file-name is the absolute name of the neighboring file presumed not to be visited in Emacs already, as that would mean that that buffer contains more up-to-date information on its diagnostics. diags is a list of diagnostic objects. When the neighboring file file-name is visited as a buffer and Flymake is activated there, the “list-only” diagnostics will not produce annotations for diags, as Flymake assumes that the Flymake activation in the new buffer will take care of that.