Re: cl-defgeneric vs random funcall in project.el

[Stephen Leake <stephen_leake@stephe-leake.org>]

Dmitry Gutov <dgutov@yandex.ru> writes:

> On 07/31/2015 02:33 AM, Stephen Leake wrote:
>
>> If the elisp project backend just used load-path as project-search-path,
>> what desired functionality would you lose?
>
> xref-find-references won't search inside the current project root.

It would help to be more specific. Since we disagree, you can't assume
I'll guess what you have in mind; my first response was "so why would
you want to?". To be truly persuasive, you need to anticipate that
response, and address it before it happens.

A concrete example directory structure:

myproj/
    # contains README, some docs

    .git/
        # contains git repo

    build/
        contains Makefile, test outputs, intermediate files
        
    lisp/
        # contains *.el files

    lisp-emacs-24.3/
        # contains *.el files only needed with emacs 24.3
        
    test/
        # contains test drivers, known good results

The user has set load-path to (".../myproj/lisp" "~/.emacs.d/elpa/..."
".../emacs-25.0/share/..." ...)

One search the user might want to do: find the name of an elisp function
in a test driver script file, to see how it is tested, while
simultaneously finding all places that function is used in the *.el
files, to review the test cases to ensure they are sufficient.

xref-find-references should do that search.

So I agree this is a case for the user adding things to
project-search-path that are not on load-path.

It would be wrong to add the entire directory tree that contains .git;
the user is using emacs 25, so they don't want to see the emacs 24.3
files. Obviously, there is a separate case where they do want to see
those files; that's a different project configuration.

We could provide:

(defun project-create (root)
 "Return a project object that has root directory ROOT.
Also enters the project in `project-root-alist'."
 ...)

`project-root-alist' associates root directories with project objects;
`project-current' walks up the current directory tree until it finds a
matching entry in the alist. If that fails, it tries the other methods
it currenty uses.

(defun project-add-search-path (project path)
 "Add PATH (a list of directories) to `project-search-path' for PROJECT.
If the directories are relative, they are first expanded relative to
`default-directory'."
 ...
 )

(defun project-add-search-ignore (project ignores)
 "Add IGNORES (a list of shell glob patterns) to `project-ignores'
for PROJECT."
 ...)

Then, in the same place they add myproj/lisp to load-path, the user
adds:

(defvar my-proj (project-create ".../myproj")) 
(project-add-search-path my-proj
  '(".../myproj/build" ".../myproj/test"))

# ignore intermediate test files
(project-add-search-ignore my-proj '(".../myproj/build/*.temp"))


xref-find-references then searches all files in all directories on
`project-search-path' and respects `project-ignores'.

-- 
-- Stephe