nix-doc
A Nix developer tool leveraging the rnix Nix parser for intelligent
documentation search and tags generation.
Features
- Nix plugin that adds a builtin that can display the signature and documentation for a lambda object in a friendly format
- Command line tool that searches Nix files in a directory for functions and shows documentation for matching ones
- Tags generator similar to
ctagsthat can generate a vim compatible tags file for Nix source - High performance, threaded implementation in Rust
Setup
# nix-doc is in nixpkgs
$ nix-env -i nix-doc
# you can alternatively get it from git
$ nix-env -i -f https://github.com/lf-/nix-doc/archive/main.tar.gz
# or if you don't want to use nix (only includes the command line tool for
# search and tags)
$ cargo install --locked nix-doc
Nix Plugin
To install the Nix plugin on a single-user installation of Nix, add this to
your Nix config at ~/.config/nix/nix.conf after installing nix-doc with
nix-env:
plugin-files = /home/YOURUSERNAMEHERE/.nix-profile/lib/libnix_doc_plugin.so
For a multi-user installation, you will need to do something like this:
$ sudo ln -s $(nix-build '<nixpkgs>' -A nix-doc) /opt/nix-doc
and then put this into your /etc/nix/nix.conf:
plugin-files = /opt/nix-doc/lib/libnix_doc_plugin.so
NixOS Installation
Link the plugin file using
nix.extraOptions:
{ pkgs, ... }:
{
nix.extraOptions = ''
plugin-files = ${pkgs.nix-doc}/lib/libnix_doc_plugin.so
'';
environment.systemPackages = with pkgs; [
nix-doc
];
}Usage
CLI
nix-doc <command>
nix-doc tags [dir]
Generates a vim-compatible tags file in the current directory, for all nix
script files below the directory dir.
Example:
nixpkgs$ nix-doc tags
nixpkgs$ file tags
tags: Exuberant Ctags tag file, ASCII text, with very long lines (502)
# opens vim to the function callCabal2nix
nixpkgs$ vim -t callCabal2nix
nix-doc search <regex> [dir]
Example output:
nixpkgs$ nix-doc search callPackage
Call the package function in the file `fn' with the required
arguments automatically. The function is called with the
arguments `args', but any missing arguments are obtained from
`autoArgs'. This function is intended to be partially
parameterised, e.g.,
callPackage = callPackageWith pkgs;
pkgs = {
libfoo = callPackage ./foo.nix { };
libbar = callPackage ./bar.nix { };
};
If the `libbar' function expects an argument named `libfoo', it is
automatically passed as an argument. Overrides or missing
arguments can be supplied in `args', e.g.
libbar = callPackage ./bar.nix {
libfoo = null;
enableX11 = true;
};
callPackageWith = autoArgs: fn: args: ...
# ./lib/customisation.nix:117
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
Like callPackage, but for a function that returns an attribute
set of derivations. The override function is added to the
individual attributes.
callPackagesWith = autoArgs: fn: args: ...
# ./lib/customisation.nix:127
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
Similar to callPackageWith/callPackage, but without makeOverridable
callPackageWith = autoArgs: fn: args: ...
# ./pkgs/development/beam-modules/lib.nix:7
Nix plugin
The Nix plugin provides three builtins:
builtins.doc f
Prints the documentation of the function f to the screen. Returns null.
builtins.getDoc f
Returns the documentation message for the function f as a string (exactly the
same output as builtins.doc, just as a string).
builtins.unsafeGetLambdaPos
A backport of NixOS/Nix#3912. Returns
the position of a lambda, in a similar fashion to unsafeGetAttrPos for
attributes.
Sample usage:
ยป nix repl
Welcome to Nix version 2.3.7. Type :? for help.
nix-repl> n=import <nixpkgs> {}
nix-repl> builtins.doc n.lib.callPackageWith
Call the package function in the file `fn' with the required
arguments automatically. The function is called with the
arguments `args', but any missing arguments are obtained from
`autoArgs'. This function is intended to be partially
parameterised, e.g.,
callPackage = callPackageWith pkgs;
pkgs = {
libfoo = callPackage ./foo.nix { };
libbar = callPackage ./bar.nix { };
};
If the `libbar' function expects an argument named `libfoo', it is
automatically passed as an argument. Overrides or missing
arguments can be supplied in `args', e.g.
libbar = callPackage ./bar.nix {
libfoo = null;
enableX11 = true;
};
func = autoArgs: fn: args: ...
# /nix/store/frpij1x0ihnyc4r5f7v0zxwpslkq6s27-nixpkgs-20.09pre237807.0dc87c6e54f/nixpkgs/lib/customisation.nix:117
null
Development
This repository is set up as a Cargo workspace with the plugin and the command line tool/library as parts.
It is not really possible to build the plugin outside a Nix shell since Nix does not provide libraries outside the shell environment. As such, it is suggested to use a nix shell while developing the plugin as follows:
$ nix-shell
[nix-shell]$ cargo build
[nix-shell]$ cargo check
[nix-shell]$ cargo test
# etc
TODO
- Tech: should update rnix to the latest major.
Related work
- NixOS/nix#1652: A PR implementing basically the same thing as this tool's plugin in Nix itself, which has been deferred indefinitely due to disagreements about what syntax to use in documentation comments.
- https://github.com/tazjin/nixdoc: A Rust tool producing DocBook documentation for Nix library functions.
- https://github.com/mlvzk/manix: An early fork of this tool with a stronger focus on CLI usage, with support for indexing and faster search. By comparison, their CLI is better, but they don't do tags or a Nix plugin.
Project information
Everyone is expected to follow the code of conduct while participating in this project.