bug#41736: 28.0.50; project.el - support global patterns for project-ignores

bug#41736: 28.0.50; project.el - support global patterns for project-ignores

[Theodor Thornhill]

Hello,

In https://debbugs.gnu.org/cgi/bugreport.cgi?bug=41572 there is talk about supporting a "plain project", and when joining that chat I realised that the "best" current implementation is the VC backend. However, this backend does not easily include other patterns to ignore.

For example we might want to ignore "node_modules", "elm-stuff" etc.
These can be added pretty easily to 'project-vc-ignores' via:

1. Major mode support: "(setq-local project-vc-ignores '("foo" "bar"))"
2. User init.el "(add-to-list project-vc-ignores "foo")"

However, there are some drawbacks.
Method 1:
- We rely on major mode to implement this
- When using "project-switch-project", then press "f - find-file" the ignore is not recognized yet since it relies on the major mode.
- It does not work when a project uses several modes

Method 2:
- Needs user to add this to own init file.
- Pollutes the defcustom globally

Is there a way to set these patters such that we still can use the fast VC backend, but not have these drawbacks?

It seems like an easy solution could be to add a "defcustom project-ignore-patterns" that the project-vc backend picks up. This could be set by both future major modes and as user customization.

FWIW, method 2 seems to work perfectly, yet seems like kind of a hack.

Theo

bug#41736: 28.0.50; project.el - support global patterns for project-ignores

[Basil L. Contovounesios]

Theodor Thornhill <theo@thornhill.no> writes:

> It seems like an easy solution could be to add a "defcustom
> project-ignore-patterns" that the project-vc backend picks up. This could be set
> by both future major modes and as user customization.

Note that defcustoms are generally a user-level preference and should
therefore generally not be modified by major modes or other Lisp.

-- 
Basil

bug#41736: 28.0.50; project.el - support global patterns for project-ignores

[Theodor Thornhill]

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On Sat, Jun 6, 2020 at 11:53, Basil L. Contovounesios <contovob@tcd.ie> wrote:

> Note that defcustoms are generally a user-level preference and should
> therefore generally not be modified by major modes or other Lisp.

> Yeah, absolutely. Unclear wording from my end.

What I mean is:

We seem to want the vc backend no matter what. However - if I open dired in root and execute “project-find-files” all the stuff I want ignored is not. I get the fast backend, but may search a million obfuscated minified files.

I think what I want is to be able to say:
1. Use the vc backed “major-mode” project
2. Use the vc backed “major-modes” project

Not sure how this would be implemented most clearly, but maybe the “project-vc-ignores” defcustom in init.el is the magic wand here?

If so - this bug report could be reduced to “add documentation to clarify this” :)

Theo

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bug#41736: 28.0.50; project.el - support global patterns for project-ignores

[Dmitry Gutov]

On 06.06.2020 12:45, Theodor Thornhill wrote:
> Hello,
> 
> In https://debbugs.gnu.org/cgi/bugreport.cgi?bug=41572 there is talk about supporting a "plain project", and when joining that chat I realised that the "best" current implementation is the VC backend. However, this backend does not easily include other patterns to ignore.
> 
> For example we might want to ignore "node_modules", "elm-stuff" etc.
> These can be added pretty easily to 'project-vc-ignores' via:
> 
> 1. Major mode support: "(setq-local project-vc-ignores '("foo" "bar"))"

I'm not sure major modes are the place to do this: after all, the user 
can call project-find-files while visiting a file in some other mode 
(say, README.md). The view of the list of project files should remain 
consistent.

> 2. User init.el "(add-to-list project-vc-ignores "foo")"
> 
> However, there are some drawbacks.
> Method 1:
> - We rely on major mode to implement this
> - When using "project-switch-project", then press "f - find-file" the ignore is not recognized yet since it relies on the major mode.

Indeed.

> - It does not work when a project uses several modes

And I think it's the common case.

> Method 2:
> - Needs user to add this to own init file.
> - Pollutes the defcustom globally
> 
> Is there a way to set these patters such that we still can use the fast VC backend, but not have these drawbacks?

How about .dir-locals.el?

project--value-in-dir takes particular care to read these files.

> It seems like an easy solution could be to add a "defcustom project-ignore-patterns" that the project-vc backend picks up. This could be set by both future major modes and as user customization.

This also either pollutes user's init.el or remains major mode specific, 
right?