mirror of
https://github.com/ryan4yin/nixos-and-flakes-book
synced 2024-11-27 06:20:29 +00:00
82 lines
4.4 KiB
Markdown
82 lines
4.4 KiB
Markdown
# Dev Environments
|
||
|
||
We have learned how to build development environments, but it's a bit tedious to write `flake.nix` for each project.
|
||
|
||
Luckily, some people in the community have done this for us. The following repository contains development environment templates for most programming languages. Just copy and paste them:
|
||
|
||
- [dev-templates](https://github.com/the-nix-way/dev-templates)
|
||
- [MordragT/nix-templates](https://github.com/MordragT/nix-templates)
|
||
|
||
If you think the structure of `flake.nix` is still too complicated and want a simpler way,
|
||
you can consider using the following project,
|
||
which encapsulates Nix more thoroughly and provides users with a simpler definition:
|
||
|
||
- [cachix/devenv](https://github.com/cachix/devenv)
|
||
|
||
|
||
If you don't want to write a single line of nix code and just want to get a reproducible development environment with minimal cost,
|
||
here's a tool that might meet your needs:
|
||
|
||
- [jetpack-io/devbox](https://github.com/jetpack-io/devbox)
|
||
|
||
## Dev Environment for Python
|
||
|
||
The development environment for Python is much more cumbersome compared to languages like Java or Go because it defaults to installing software in the global environment.
|
||
To install software for the current project, you must create a virtual environment first (unlike in languages such as JavaScript or Go,
|
||
where virtual environments are not necessary). This behavior is very unfriendly for Nix.
|
||
|
||
By default, when using pip in Python, it installs software globally. On NixOS, running `pip install` directly will result in an error:
|
||
|
||
```bash
|
||
› pip install -r requirements.txt
|
||
error: externally-managed-environment
|
||
|
||
× This environment is externally managed
|
||
╰─> This command has been disabled as it tries to modify the immutable
|
||
`/nix/store` filesystem.
|
||
|
||
To use Python with Nix and nixpkgs, have a look at the online documentation:
|
||
<https://nixos.org/manual/nixpkgs/stable/#python>.
|
||
|
||
note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
|
||
hint: See PEP 668 for the detailed specification.
|
||
```
|
||
|
||
Based on the error message, `pip install` is directly disabled by NixOS. Even when attempting `pip install --user`, it is similarly disabled.
|
||
To improve the reproducibility of the environment, Nix eliminates these commands altogether.
|
||
Even if we create a new environment using methods like `mkShell`,
|
||
these commands still result in errors (presumably because the pip command in Nixpkgs itself has
|
||
been modified to prevent any modification instructions like `install` from running).
|
||
|
||
However, many project installation scripts are based on pip, which means these scripts cannot be used directly.
|
||
Additionally, the content in nixpkgs is limited, and many packages from PyPI are missing.
|
||
This requires users to package them themselves, adding a lot of complexity and mental burden.
|
||
|
||
One solution is to use the `venv` virtual environment. Within a virtual environment, you can use commands like pip normally:
|
||
|
||
```shell
|
||
python -m venv ./env
|
||
source ./env/bin/activate
|
||
```
|
||
|
||
Alternatively, you can use a third-party tool called `virtualenv`, but this requires additional installation.
|
||
|
||
For those who still lack confidence in the venv created directly with Python, they may prefer to include the virtual environment in `/nix/store` to make it immutable.
|
||
This can be achieved by directly installing the dependencies from `requirements.txt` or `poetry.toml` using Nix.
|
||
There are existing Nix packaging tools available to assist with this:
|
||
|
||
> Note that even in these environments, running commands like `pip install` directly will still fail.
|
||
Python dependencies must be installed through `flake.nix` because the data is located in the `/nix/store` directory,
|
||
and these modification commands can only be executed during the Nix build phase.
|
||
|
||
- [DavHau/mach-nix](https://github.com/DavHau/mach-nix)
|
||
- [poetry2nix](https://github.com/nix-community/poetry2nix)
|
||
|
||
The advantage of these tools is that they utilize the lock mechanism of Nix Flakes to improve reproducibility.
|
||
However, the downside is that they add an extra layer of abstraction, making the underlying system more complex.
|
||
|
||
|
||
Finally, in some more complex projects, neither of the above solutions may be feasible.
|
||
In such cases, the best solution is to use containers such as Docker or Podman. Containers have fewer restrictions compared to Nix and can provide the best compatibility.
|
||
|
||
|