bootstrap lib, add mkDevShell

3 files changed, 107 insertions, 0 deletions

diff --git a/flake.nix b/flake.nix
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--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,9 @@
+{
+  description = "Additional flake utils for convenience.";
+
+  outputs = { self }: {
+    lib = {
+      mkDevShell = import ./lib/mk-dev-shell.nix;
+    };
+  };
+}
diff --git a/lib/mk-dev-shell.nix b/lib/mk-dev-shell.nix
new file mode 100644
index 0000000..e0bb441
--- /dev/null
+++ b/lib/mk-dev-shell.nix
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+{ pkgs
+, tools ? []
+, envVars ? {}
+}:
+
+let
+  # TODO: escape values properly
+  exportEnvVar = k: v: ''export ${k}="${v}"; echo ${k}=\"${v}\"'';
+  exportedEnvVars = pkgs.lib.mapAttrsToList exportEnvVar envVars;
+
+in pkgs.mkShell {
+  buildInputs = tools;
+
+  # TODO: handle case with no env variable set
+  # TODO: handle case with no package in tools
+  # TODO: allow custom shell
+  shellHook = ''
+    echo -e "\nDEVSHELL ENVIRONMENT VARIABLES:"
+    ${pkgs.lib.concatStringsSep "\n" exportedEnvVars}
+
+    echo -e "\nDEVSHELL COMMANDS:"
+    ls "${pkgs.symlinkJoin { name = "env"; paths = tools; }}/bin"
+
+    # Use the default user shell instead of Bash
+    $(${pkgs.finger_bsd}/bin/finger $USER \
+      | ${pkgs.gnugrep}/bin/grep -oP 'Shell: \K.*')
+
+    exit $?
+  '';
+}
diff --git a/readme.md b/readme.md
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+++ b/readme.md
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+# flaky-utils
+
+Additional Nix Flake utility functions for personal convenience (mainly
+reducing boilerplate).
+
+No promise on API stability.
+
+
+## Usage
+
+Functions documentation provided as comments below.
+
+```nix
+{
+  description = "Example of a Flake using flaky-utils.";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.05";
+    flake-utils.url = "github:numtide/flake-utils";
+    flaky-utils.url = "git+https://cgit.pacien.net/libs/flaky-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, flaky-utils }:
+  flake-utils.lib.eachDefaultSystem (system: let
+    pkgs = import nixpkgs { inherit system; };
+  in {
+
+    # Convenience development shell providing some tools.
+    #
+    # The binaries made available and the environment variable set are printed
+    # when entering the shell.
+    #
+    # The user's default shell is used instead of Bash (sacrifying a bit of
+    # reproducibility for convenience).
+    #
+    devShell = flaky-utils.lib.mkDevShell {
+      inherit pkgs;
+
+      tools = with pkgs; [
+        postgresql_14
+        pgcli
+      ];
+
+      envVars = rec {
+        PGDATA = "$PWD/development_database/pgdata";
+        PGHOST = "$PWD/development_database";
+        PGPORT = "5432";
+        PGDATABASE = "app";
+        DATABASE_URL = "postgresql:///${PGDATABASE}?host=${PGHOST}";
+      };
+    };
+
+  });
+}
+```
+
+
+## Contributing
+
+Issues and patches: email the author.
+
+
+## Licence and copyright
+
+Copyright (C) 2022 Pacien TRAN-GIRARD.
+
+This project is distributed under the terms of European Union Public Licence
+version 1.2, a copy of which is provided in `./licence.txt`.