nix-community/nix-direnv
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Merge pull request #23 from purcell/patch-1

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@ -2,17 +2,18 @@
![Test](https://github.com/nix-community/nix-direnv/workflows/Test/badge.svg) ![Test](https://github.com/nix-community/nix-direnv/workflows/Test/badge.svg)
A fast, persistent use_nix implementation for direnv. A faster, persistent implementation of `direnv`'s `use_nix`, to replace the built-in one.
Prominent features: Prominent features:
- significantly faster after the first run by caching the nix-shell environment - significantly faster after the first run by caching the `nix-shell` environment
- prevents garbage collection of build dependencies by symlinking the resulting - prevents garbage collection of build dependencies by symlinking the resulting
shell derivation in the user's `gcroots` (Life is too short to loose your shell derivation in the user's `gcroots` (Life is too short to lose
build cache of your project if you are in a plane without internet connection) your project's build cache if you are on a flight with no internet connection)
## Installation via nix ## Installation via Nix
Since 20.03 you can install nix-direnv via nix: Since 20.03 you can install `nix-direnv` via nix:
### NixOS ### NixOS
@ -32,7 +33,7 @@ In `/etc/nixos/configuration.nix`:
} }
``` ```
Then source the direnvrc from this repository in your own `.direnvrc` Then source the `direnvrc` from this repository in your own `.direnvrc`
```bash ```bash
# put this in ~/.direnvrc # put this in ~/.direnvrc
@ -58,7 +59,7 @@ In `$HOME/.config/nixpkgs/home.nix` add
} }
``` ```
Optional: To protect your nix-shell against garbage collection you also need to add these options to your nix configuration Optional: To protect your nix-shell against garbage collection you also need to add these options to your Nix configuration.
If you are on NixOS also add the following lines to your `/etc/nixos/configuration.nix`: If you are on NixOS also add the following lines to your `/etc/nixos/configuration.nix`:
@ -71,7 +72,7 @@ If you are on NixOS also add the following lines to your `/etc/nixos/configurati
} }
``` ```
On other systems with nix add the following configuration to your `/etc/nix/nix.conf`: On other systems with Nix add the following configuration to your `/etc/nix/nix.conf`:
``` ```
keep-derivations = true keep-derivations = true
@ -105,13 +106,15 @@ source $HOME/nix-direnv/direnvrc
## Storing .direnv outside the project directory ## Storing .direnv outside the project directory
`.direnv` might interact badly with backups (i.e. Dropbox) or IDEs. A `.direnv` directory will be created in each `use_nix` project, which might
Therefore it's possible to override in `$HOME/.config/direnv/direnvrc` or interact badly with backups (e.g. Dropbox) or IDEs.
in own project's `.envrc` a variable called `$direnv_layout_dir`.
Therefore it's possible to override a variable called `$direnv_layout_dir` in
`$HOME/.config/direnv/direnvrc` or in each project's `.envrc`.
The following example will create a unique directory name per project The following example will create a unique directory name per project
in `$HOME/.cache/direnv/layouts/`: in `$HOME/.cache/direnv/layouts/`:
```bash ```bash
# $HOME/.config/direnv/direnvrc # $HOME/.config/direnv/direnvrc
: ${XDG_CACHE_HOME:=$HOME/.cache} : ${XDG_CACHE_HOME:=$HOME/.cache}
@ -121,18 +124,17 @@ direnv_layout_dir=$XDG_CACHE_HOME/direnv/layouts/$pwd_hash
## Known Bugs ## Known Bugs
At the moment nix-direnv depends on gnugrep and a modern bash version. At the moment `nix-direnv` depends on GNU Grep and a modern Bash version.
This might lead to [problems](https://github.com/nix-community/nix-direnv/issues/3) on macOS. This might lead to [problems](https://github.com/nix-community/nix-direnv/issues/3) on macOS.
As a work-around we suggest to install direnv/grep via nix or homebrew. As a work-around we suggest that macOS users install `direnv`/`grep` via Nix or Homebrew.
## Why not using lorri instead? ## Why not use `lorri` instead?
Lorri causes large CPU load when `$NIXPKGS` is pointed to a directory, i.e. a Lorri causes large CPU load when `$NIXPKGS` is pointed to a directory, e.g. a
git checkout. This is because it tries to watch any referenced nix file and git checkout. This is because it tries to watch all referenced Nix files and
re-evaluates if those changes. Nix-direnv comprises between performance and re-evaluate them when they change. Nix-direnv compromises between performance and
correctness and only reevaluate direnv if either the project-specific correctness, and only re-evaluates direnv if either the project-specific
`default.nix` / `shell.nix` changes or if there is a new commit added to `default.nix` / `shell.nix` changes, or if there is a new commit added to
`nixpkgs`. A re-evaluation can be also triggered by using `touch shell.nix` in `nixpkgs`. A re-evaluation can be also triggered by using `touch shell.nix` in
the same project. Also `nix-direnv` does not require additional software besides the same project. Also `nix-direnv` does not require an additional daemon, so it can be
`direnv` + `nix` i.e. a daemon and the function could be included into the included into the project itself and enabled without further user effort.
project itself.