deadnix
Scan .nix files for dead code (unused variable bindings).
Usage with Github Actions
See deadnix-action
Usage with Nix Flakes
Help
$ nix run github:astro/deadnix -- --help
USAGE:
deadnix [OPTIONS] [FILE_PATHS]...
ARGS:
<FILE_PATHS>... .nix files, or directories with .nix files inside [default: .]
OPTIONS:
-_, --no-underscore
Don't check any bindings that start with a _
-e, --edit
Remove unused code and write to source file
-f, --fail
Exit with 1 if unused code has been found
-h, --hidden
Recurse into hidden subdirectories and process hidden .*.nix files
--help
Print help information
-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)
-o, --output-format <OUTPUT_FORMAT>
Output format to use [default: human-readable] [possible values: human-readable, json]
-q, --quiet
Don't print dead code report
-V, --version
Print version information
Reports contain ANSI color escape codes unless the
$NO_COLOR environment variable is set.
Scan for unused code
$ nix run github:astro/deadnix test.nix
Warning: Unused declarations were found.
╭─[example.nix:1:1]
│
1 │ unusedArgs@{ unusedArg, usedArg, ... }:
· ─────┬──── ────┬────
· │ ╰────── Unused lambda pattern: unusedArg
· │
· ╰────────────────── Unused lambda pattern: unusedArgs
3 │ inherit (builtins) unused_inherit;
· ───────┬──────
· ╰──────── Unused let binding: unused_inherit
5 │ unused = "fnord";
· ───┬──
· ╰──── Unused let binding: unused
10 │ shadowed = 42;
· ────┬───
· ╰───── Unused let binding: shadowed
11 │ _unused = unused: false;
· ───┬─── ───┬──
· │ ╰──── Unused lambda argument: unused
· │
· ╰────────────── Unused let binding: _unused
13 │ x = { unusedArg2, x ? args.y, ... }@args: used1 + x;
· ─────┬────
· ╰────── Unused lambda pattern: unusedArg2
────╯
Remove unused code automatically
Do commit your changes into version control before!
$ nix run github:astro/deadnix -- -eq test.nix
Behavior
Renaming of all unused to lambda args to start with _
If you disfavor marking them as unused, use option --no-lambda-arg.
nixpkgs callPackages with multiple imports
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 --no-lambda-pattern-names in this case.
What if the produced reports are wrong?
Please open an issue. Do not forget to include the .nix code that
produces incorrect results.
Commercial Support
The author can be hired to implement the features that you wish, or to integrate this tool into your toolchain.