Scan .nix
files for dead code (unused variable bindings).
See deadnix-action
nix run github:astro/deadnix -- --help
Find dead code in .nix files
Usage: deadnix [OPTIONS] [FILE_PATHS]...
Arguments:
[FILE_PATHS]... .nix files, or directories with .nix files inside [default: .]
Options:
-l, --no-lambda-arg Don't check lambda parameter arguments
-L, --no-lambda-pattern-names Don't check lambda attrset pattern names (don't break nixpkgs callPackage)
-_, --no-underscore Don't check any bindings that start with a _
-q, --quiet Don't print dead code report
-e, --edit Remove unused code and write to source file
-h, --hidden Recurse into hidden subdirectories and process hidden .*.nix files
--help
-f, --fail Exit with 1 if unused code has been found
-o, --output-format <OUTPUT_FORMAT> Output format to use [default: human-readable] [possible values: human-readable, json]
--exclude <EXCLUDES>... Files to exclude from analysis
-V, --version Print version
Reports contain ANSI color escape codes unless the
$NO_COLOR
environment variable is set.
The --exclude
parameter accepts multiple paths. Separate them with
--
to pass [FILE_PATHS]...
.
nix run github:astro/deadnix example.nix
Warning: Unused declarations were found.
โญโ[example.nix:1:1]
1 โunusedArgs@{ unusedArg, usedArg, ... }:
ยท โ โฐโโโโโ Unused lambda pattern: unusedArg
ยท โฐโโโโโโโโโโโโโโโโโ Unused lambda pattern: unusedArgs
3 โ inherit (builtins) unused_inherit;
ยท โฐโโโโโโโ Unused let binding: unused_inherit
5 โ unused = "fnord";
ยท โฐโโโ Unused let binding: unused
10 โ shadowed = 42;
ยท โฐโโโโ Unused let binding: shadowed
11 โ _unused = unused: false;
ยท โ โฐโโโ Unused lambda argument: unused
ยท โฐโโโโโโโโโโโโโ Unused let binding: _unused
13 โ x = { unusedArg2, x ? args.y, ... }@args: used1 + x;
ยท โฐโโโโโ Unused lambda pattern: unusedArg2
Do commit your changes into version control before!
nix run github:astro/deadnix -- -eq test.nix
Usage with pre-commit
Add the following to your project's .pre-commit-config.yaml
:
repos:
- repo: https://github.com/astro/deadnix
rev: ID # frozen: VERSION
hooks:
- id: deadnix
#args: [--edit] # Uncomment to automatically modify files
stages: [commit]
Replace ID
and VERSION
above with the relevant version tag and
commit ID for reference, for example:
rev: da39a3ee5e6b4b0d3255bfef95601890afd80709 # frozen: v1.2.3
If you disfavor marking them as unused, use option
-l
/--no-lambda-arg
.
callPackages
guesses the packages to inject by the names of a
packages' lambda attrset pattern names. Some packages alias these with
@args
to pass them to another import ...nix args
.
As the used args are only named in the imported file they will be
recognized as dead in the package source file that is imported by
callPackage
, rendering it unable to guess the dependencies to call
the packages with.
Use option -L
/--no-lambda-pattern-names
in this case.
As of 1.1.0 deadnix supports the following pragma to skip check of bindings in the following line:
# deadnix: skip
Please open an issue. Do not forget to include the .nix
code that
produces incorrect results.
The author can be hired to implement the features that you wish, or to integrate this tool into your toolchain.