feat: add option to install tool

README.md

@@ -35,6 +35,7 @@ env = devshell-lib.lib.mkDevShell {
   inherit system;
   src = ./.;
   extraPackages = [ ];
+  preToolHook = "";
   tools = [ ];
   additionalHooks = { };
 };
@@ -46,6 +47,30 @@ Expose it in `devShells` as `default` and run:
 nix develop
 ```
 
+Use `preToolHook` when a tool needs bootstrap work before the shell prints tool versions. This is useful for tools you install outside `nixpkgs`, as long as the hook is idempotent.
+
+```nix
+env = devshell-lib.lib.mkDevShell {
+  inherit system;
+  src = ./.;
+
+  # assumes `go` is already available in PATH, for example via `extraPackages`
+
+  preToolHook = ''
+    export GOBIN="$PWD/.tools/bin"
+    export PATH="$GOBIN:$PATH"
+
+    if ! command -v golangci-lint >/dev/null 2>&1; then
+      go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
+    fi
+  '';
+
+  tools = [
+    { name = "golangci-lint"; bin = "golangci-lint"; versionCmd = "version"; color = "YELLOW"; }
+  ];
+};
+```
+
 ## Common commands
 
 ```bash

flake.nix

@@ -34,12 +34,15 @@
             system,
             src ? ./.,
             extraPackages ? [ ],
+            preToolHook ? "",
             extraShellHook ? "",
             additionalHooks ? { },
             tools ? [ ],
             includeStandardPackages ? true,
             # tools = list of { name, bin, versionCmd, color? }
             # e.g. { name = "Bun"; bin = "${pkgs.bun}/bin/bun"; versionCmd = "--version"; color = "YELLOW"; }
+            # preToolHook = shell snippet that runs before the ready banner and tool logs
+            # e.g. install tools outside nixpkgs, export PATH updates, warm caches
             formatters ? { },
             # formatters = treefmt-nix programs attrset, merged over { nixfmt.enable = true; }
             # e.g. { gofmt.enable = true; shfmt.enable = true; }
@@ -144,6 +147,8 @@
                 UNDERLINE='\033[4m'
                 RESET='\033[0m'
 
+                ${preToolHook}
+
                 printf "\n$GREEN 🚀 Dev shell ready$RESET\n\n"
                 ${toolBannerScript}
                 printf "\n"

template/flake.nix

@@ -66,8 +66,20 @@
           # { name = "Bun";   bin = "${pkgs.bun}/bin/bun";    versionCmd = "--version"; color = "YELLOW"; }
           # { name = "Go";    bin = "${pkgs.go}/bin/go";       versionCmd = "version";   color = "CYAN";   }
           # { name = "Rust";  bin = "${pkgs.rustc}/bin/rustc"; versionCmd = "--version"; color = "YELLOW"; }
+          # { name = "golangci-lint"; bin = "golangci-lint"; versionCmd = "version"; color = "YELLOW"; }
         ];
 
+        preToolHook = ''
+          # runs before the ready banner + tool version logs
+          # useful for installing tools outside nixpkgs and updating PATH first
+          #
+          # export GOBIN="$PWD/.tools/bin"
+          # export PATH="$GOBIN:$PATH"
+          # if ! command -v golangci-lint >/dev/null 2>&1; then
+          #   go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest
+          # fi
+        '';
+
         extraShellHook = ''
           # any repo-specific shell setup here
         '';