lix-project/lix

Fork 54

Deprecate `nix eval`'s strange and poorly documented `--write-to` argument #227

New issue

Closed

opened 2024-04-06 03:48:28 +00:00 by lunaphied · 6 comments

lunaphied commented

2024-04-06 03:48:28 +00:00

Owner

The argument is described in the manpage simply as: --write-to path Write a string or attrset of strings to path.

However, in reality what it actually does is:

--write-to, specifically if a nix expression evaluates to an attrset of strings (or an attrset of attrsets of strings, etc), creates a directory tree where each leaf attribute becomes a file with the attr name as its file name and the attr string value as its contents

Which as @qyriad has noted, seems incredibly specific.

At the very least this option's documentation needs an update in the manpage to match the help output which is:

With --write-to path, the evaluation result must be a string or a nested attribute set whose leaf values are strings. These strings are written to files named path/attrpath. path must not already exist.

And potentially this functionality should be considered for deprecation and removal or at least a usage survey should be conducted

The argument is described in the manpage simply as: `--write-to path Write a string or attrset of strings to path.` However, in reality what it actually does is: > `--write-to`, specifically if a nix expression evaluates to an attrset of strings (or an attrset of attrsets of strings, etc), creates a directory tree where each leaf attribute becomes a file with the attr name as its file name and the attr string value as its contents Which as @qyriad has noted, seems incredibly specific. At the very least this option's documentation needs an update in the manpage to match the help output which is: ``` With --write-to path, the evaluation result must be a string or a nested attribute set whose leaf values are strings. These strings are written to files named path/attrpath. path must not already exist. ``` And potentially this functionality should be considered for deprecation and removal or at least a usage survey should be conducted

lunaphied added the

docs

labels

2024-04-06 03:48:28 +00:00

qyriad commented

2024-04-06 03:50:34 +00:00

Owner

And potentially this functionality should be considered for deprecation and removal or at least a usage survey should be conducted

idk, converting a Nix expression to a directory structure is kind of…neat, I suppose; I'm not sure we should remove that entirely, but both the mechanism and the interface for it could use some design work.

> And potentially this functionality should be considered for deprecation and removal or at least a usage survey should be conducted idk, converting a Nix expression to a directory structure *is* kind of…neat, I suppose; I'm not sure we should remove that entirely, but both the mechanism and the interface for it could use some design work.

👍 1

jade commented

2024-04-06 04:10:48 +00:00

Owner

honestly the more sensible replacement for this is probably building this thing as a derivation? like, via puck's NAR builder tricks, if operationalized at least.

honestly the more sensible replacement for this is *probably* building this thing as a derivation? like, via puck's NAR builder tricks, if operationalized at least.

qyriad commented

2024-04-06 04:36:44 +00:00

Owner

It's currently used to generate the mdbook versions of the nix3 CLI man pages, so at the least replacing --write-to with building inside a derivation wouldn't really work for that use case, though that use case is kind of wild in the first place

It's currently used to generate the mdbook versions of the nix3 CLI man pages, so at the least replacing `--write-to` with building inside a derivation wouldn't really work for that use case, though that use case is kind of wild in the first place

jade commented

2024-04-06 04:37:25 +00:00

Owner

oh we suppose this could be good for use cases where you don't have a daemon. fair enough.

jade changed title from ~~nix eval has very strange and poorly documented --write-to argument~~ to Deprecate nix eval's strange and poorly documented --write-to argument

2024-04-09 02:52:44 +00:00

jade commented

2024-04-09 03:00:38 +00:00

Owner

Discussion was had with the team, outcome:

Stop using it ourselves, it is not a good feature. Replace it with a Python script that does what we want with the JSON output
It appears that nobody uses this outside of Nix and its forks, so we can remove it, but, to be polite:
Deprecate --write-to, adding a warning, then remove it in a later release

Discussion was had with the team, outcome: - Stop using it ourselves, it is not a good feature. Replace it with a Python script that does what we want with the JSON output - It appears that nobody uses this outside of Nix and its forks, so we can remove it, but, to be polite: - Deprecate `--write-to`, adding a warning, then remove it in a later release

jade added the

E/help wanted

label

2024-09-26 00:47:21 +00:00

jade referenced this issue

2025-08-21 14:42:07 +00:00

delete nix eval --write-to #974

pennae was assigned by jade

2025-08-21 21:15:11 +00:00

lix-bot commented

2025-08-22 12:31:21 +00:00

Member

This issue was mentioned on Gerrit on the following CLs:

commit message in cl/4045 ("nix/eval: remove --write-to")

This issue was mentioned on Gerrit on the following CLs: * commit message in [cl/4045](https://gerrit.lix.systems/c/lix/+/4045) ("nix/eval: remove --write-to")