add 'fmt' mode

README.md

@@ -239,6 +239,7 @@ process, rest is passed-through into `mkDerivation`.
 | `cargoTestCommands` | The commands to run in the `checkPhase`. Do not forget to set [`doCheck`](https://nixos.org/nixpkgs/manual/#ssec-check-phase). The argument must be a function modifying the default value. <br/> Default: `[ ''cargo $cargo_options test $cargo_test_options'' ]` |
 | `cargoTestOptions` | Options passed to cargo test, i.e. `cargo test <OPTS>`. These options can be accessed during the build through the environment variable `cargo_test_options`. <br/> Note: these values are not (shell) escaped, meaning that you can use environment variables but must be careful when introducing e.g. spaces. <br/> The argument must be a function modifying the default value. <br/> Default: `[ "$cargo_release" ''-j "$NIX_BUILD_CORES"'' ]` |
 | `cargoClippyOptions` | Options passed to cargo clippy, i.e. `cargo clippy -- <OPTS>`. These options can be accessed during the build through the environment variable `cargo_clippy_options`. <br /> Note: these values are not (shell) escaped, meaning that you can use environment variables but must be careful when introducing e.g. spaces. <br/> The argument must be a function modifying the default value. <br/> Default: `[ "-D warnings" ]` |
+| `cargoFmtOptions` | Options passed to cargo fmt, i.e. `cargo fmt -- <OPTS>`. These options can be accessed during the build through the environment variable `cargo_fmt_options`. <br /> Note: these values are not (shell) escaped, meaning that you can use environment variables but must be careful when introducing e.g. spaces. <br/> The argument must be a function modifying the default value. <br/> Default: `[ "--check" ]` |
 | `nativeBuildInputs` | Extra `nativeBuildInputs` to all derivations. Default: `[]` |
 | `buildInputs` | Extra `buildInputs` to all derivations. Default: `[]` |
 | `cargoOptions` | Options passed to all cargo commands, i.e. `cargo <OPTS> ...`. These options can be accessed during the build through the environment variable `cargo_options`. <br/> Note: these values are not (shell) escaped, meaning that you can use environment variables but must be careful when introducing e.g. spaces. <br/> The argument must be a function modifying the default value. <br/> Default: `[ ]` |
@@ -260,7 +261,7 @@ process, rest is passed-through into `mkDerivation`.
 | `copyTarget` | When true, the `target/` directory is copied to `$out`. Default: `false` |
 | `postInstall` | Optional hook to run after the compilation is done; inside this script, `$out/bin` contains compiled Rust binaries. Useful if your application needs e.g. custom environment variables, in which case you can simply run `wrapProgram $out/bin/your-app-name` in here. Default: `false` |
 | `usePureFromTOML` | Whether to use the `fromTOML` built-in or not. When set to `false` the python package `remarshal` is used instead (in a derivation) and the JSON output is read with `builtins.fromJSON`. This is a workaround for old versions of Nix. May be used safely from Nix 2.3 onwards where all bugs in `builtins.fromTOML` seem to have been fixed. Default: `true` |
-| `mode` | What to do when building the derivation. Either `build`, `check`, `test` or `clippy`. <br/> When set to something other than `build`, no binaries are generated. Default: `"build"` |
+| `mode` | What to do when building the derivation. Either `build`, `check`, `test`, `fmt` or `clippy`. <br/> When set to something other than `build`, no binaries are generated. Default: `"build"` |
 
 
 ## Examples

build.nix

@@ -39,6 +39,7 @@
   #  significantly reducing the Nix closure size.
 , removeReferencesToSrcFromDocs
 , cargoClippyOptions
+, cargoFmtOptions
 , mode ? "build" # `build`, `check`, `test` or `clippy`
 , gitDependencies
 , pname
@@ -142,6 +143,7 @@ let
     cargo_build_options = cargoBuildOptions;
     cargo_test_options = cargoTestOptions;
     cargo_clippy_options = cargoClippyOptions;
+    cargo_fmt_options = cargoFmtOptions;
     cargo_doc_options = cargoDocOptions;
     cargo_bins_jq_filter = copyBinsFilter;
     cargo_libs_jq_filter = copyLibsFilter;

config.nix

@@ -82,6 +82,14 @@ let
     cargoClippyOptions =
       allowFun attrs0 "cargoClippyOptions" [ "-D warnings" ];
 
+    # Options passed to cargo fmt, i.e. `cargo fmt -- <OPTS>`. These options
+    # can be accessed during the build through the environment variable
+    # `cargo_fmt_options`. <br />
+    # Note: these values are not (shell) escaped, meaning that you can use
+    # environment variables but must be careful when introducing e.g. spaces. <br/>
+    cargoFmtOptions =
+      allowFun attrs0 "cargoFmtOptions" [ "--check" ];
+
     # Extra `nativeBuildInputs` to all derivations.
     nativeBuildInputs = attrs0.nativeBuildInputs or [];
 
@@ -189,7 +197,7 @@ let
     # fixed.
     usePureFromTOML = attrs0.usePureFromTOML or true;
 
-    # What to do when building the derivation. Either `build`, `check`, `test` or `clippy`. <br/>
+    # What to do when building the derivation. Either `build`, `check`, `test`, `fmt` or `clippy`. <br/>
     # When set to something other than `build`, no binaries are generated.
     mode = attrs0.mode or "build";
   };
@@ -257,6 +265,8 @@ let
         ''cargo $cargo_options test $cargo_test_options >> $cargo_build_output_json''
       else if (mode == "clippy") then
         ''cargo $cargo_options clippy $cargo_build_options -- $cargo_clippy_options >> $cargo_build_output_json''
+      else if (mode == "fmt") then
+        ''cargo $cargo_options fmt -- $cargo_fmt_options''
       else throw "Unknown mode ${mode}, allowed modes: build, check, test, clippy";
 
   # config used during build the prebuild and the final build
@@ -284,6 +294,7 @@ let
       cargoTestOptions
 
       cargoClippyOptions
+      cargoFmtOptions
 
       doDoc
       doDocFail