Import direnv

en/dev.md

@@ -2,7 +2,10 @@
 
 While package management is the key purpose of #[[nix]], its [[drv|derivations]] can also be used to produce non-package types, such as development environments (aka. "devShell").
 
-## Development Environments
+## Language support
 
-- Languages
-  - [[haskell]]#
+- [[haskell]]#
+
+## Tools
+
+- [[direnv]]#

en/direnv.md

@@ -0,0 +1,80 @@
+# `direnv`: manage dev environments
+
+`direnv` (along with [nix-direnv]) allows one to persist[^gc] nix #[[dev|devshell]] environments and share them seamlessly with text editors and IDEs. It obviates having to run `nix develop` manually every time you open a new terminal. The moment you `cd` into your project directory, the devshell is automatically activated, thanks to `direnv`. 
+
+[^gc]: [nix-direnv] prevents garbage collection of the devshell, so you do not have to re-download things again. direnv also enables activating the devshell in your current shell, without needing to use a customized bash.
+
+>[!tip] Starship
+> It is recommended to use [**starship**](https://starship.rs/) along with nix-direnv, because it gives a visual indication of the current environment. For example, if you are in a `nix develop` shell, your terminal prompt automatically changes to something like this:
+>
+> ```sh
+> srid on nixos haskell-template on  master [!] via λ 9.2.6 via ❄️  impure (ghc-shell-for-haskell-template-0.1.0.0-0-env)
+> ❯
+> ```
+
+## Setup 
+
+:::{class="flex items-center justify-center mb-8"}
+<iframe width="560" height="315" src="https://www.youtube.com/embed/1joZLTgYLxY?si=ljZLcFAIhrJ7XawV" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>
+:::
+
+
+
+
+If you use [[home-manager]], both `nix-direnv` and `starship` can be installed using the following configuration:
+
+```nix
+# home.nix
+programs.direnv = {
+  enable = true;
+  nix-direnv.enable = true;
+};
+programs.starship = {
+  enable = true;
+};
+```
+
+>[!tip] Newcomer Tip
+> If you have never used [[home-manager]] before, we recommend that you set it up[^nf] by following the instrutions at https://github.com/juspay/nix-dev-home.
+
+[^nf]: The "nix-dev-home" template uses [nixos-flake](https://community.flake.parts/nixos-flake), and works on both Linux or macOS.
+
+### Text Editor configuration
+
+#### VSCode
+
+For VSCode, use [Martin Kühl's direnv extension](https://marketplace.visualstudio.com/items?itemName=mkhl.direnv).
+
+#### Doom Emacs
+
+Doom Emacs has the [`:tools` `direnv` module](https://github.com/doomemacs/doomemacs/tree/master/modules/tools/direnv) to automatically load the devshell environment when you open the project directory.
+
+## Add a `.envrc`
+
+To enable direnv on Flake-based projects, add the following to your `.envrc`:
+
+```text title=".envrc"
+use flake
+```
+
+Now run `direnv allow` to authorize the current `.envrc` file. You can now `cd` into the project directory in a terminal and the devshell will be automatically activated.
+
+### Reload automatically when some files change
+
+#### [[haskell]] - when `.cabal` files change
+
+Since both [nixpkgs](https://community.flake.parts/haskell-flake/nixpkgs-haskell) and [haskell-flake](https://community.flake.parts/haskell-flake) use Nix expressions that read the `.cabal` file to get dependency information, you will want the devshell be recreated every time a `.cabal` file changes. This can be achieved using the `nix_direnv_watch_file` function. Modify your `.envrc` to contain:
+
+```text title=".envrc"
+nix_direnv_watch_file *.cabal
+use flake
+```
+
+As a result of this whenever you change a `.cabal` file, direnv will reload the environment. If you are using VSCode, you will see a notification that the environment has changed, prompting you to restart it ([see example](https://github.com/nammayatri/nammayatri/tree/main/Backend#visual-studio-code)).
+
+## External Links
+
+- [Effortless dev environments with Nix and direnv](https://determinate.systems/posts/nix-direnv)
+
+[nix-direnv]: https://github.com/nix-community/nix-direnv
+[home-manager]: https://github.com/nix-community/home-manager

en/home-manager.md

@@ -0,0 +1,6 @@
+
+https://github.com/nix-community/home-manager
+
+## Getting Started
+
+https://github.com/juspay/nix-dev-home