RemoandGitHub
dbc3aa28c4
* Integrate the style and lint dependencies with Nix * Add documentation on the nix styling scripts.
113 lines
3.9 KiB
Markdown
113 lines
3.9 KiB
Markdown
# Nix development and build environment
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With Nix it's possible to quickly and reliably recreate the full environments
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for developing, testing and building PostgREST.
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## Getting started with Nix
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You'll need to [get Nix](https://nixos.org/download.html). The installer will
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create your Nix store in the `/nix/` directory, where all build artifacts and
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their dependencies will be stored. It will also link the Nix executables like
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`nix-env`, `nix-build` and `nix-shell` into your PATH. Nix will manage all
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other PostgREST dependencies from here on out. To clean up older build
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artifacts from the `/nix/store`, you can run `nix-collect-garbage`.
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## Building PostgREST
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To build PostgREST from your local checkout of the repository, run:
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```bash
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nix-build --attr postgrest
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```
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This will create a `result` directory that contains the PostgREST binary at
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`result/bin/postgrest`. The `--attr` parameter (or short: `-A`) tells Nix to
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build the `postgrest` attribute from the Nix expression it finds in our
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`default.nix` (see below for details). Nix will take care of getting the right
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GHC version and all the build dependencies.
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## Developing
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A development environment for PostgREST is available with `nix-shell`. The
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following command will put you into a new shell that has GHC and Cabal on the
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PATH:
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```bash
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nix-shell
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```
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Within `nix-shell`, you can run Cabal commands as usual. You can also run
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stack with the `--nix` option, which causes stack to pick up the non-Haskell
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dependencies from the same pinned Nixpkgs version that the Nix builds use.
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## Testing
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In nix-shell, you'll find utility scripts that make it very easy to run the
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Haskell test suite, including setting up all required dependencies and
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temporary test databases:
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```bash
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# Run the tests against the most recent version of PostgreSQL:
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nix-shell --run postgrest-test-spec
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# Run the tests against all supported versions of PostgreSQL:
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nix-shell --run postgrest-test-spec-all
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# Run the tests against a specific version of PostgreSQL (use tab-completion in
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# nix-shell to see all available versions):
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nix-shell --run postgrest-test-spec-postgresql-9.5.21
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```
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## Linting and styling code
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The nix-shell also contains scripts for linting and styling the PostgREST
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source code:
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```bash
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# Linting
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nix-shell --run postgrest-lint
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# Styling / auto-formatting code
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nix-shell --run postgrest-style
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```
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## Tour
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The following is not required for working on PostgREST with Nix, but it will
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give you some more background and details on how it works.
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### `default.nix`
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[`default.nix`](../default.nix) is our 'respository expression' that pulls all
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the pieces that we define with Nix together. It returns a set (like a dict in
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other programming languages), where each attribute is a derivation that Nix
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knows how to build, like the `postgrest` attribute from earlier.
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Internally, our `default.nix` uses the `pkgs.callPackage` function to import
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the modules that we defined in the `nix` directory. It automatically passes the
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arguments those modules require if they are available in `pkgs` (this means
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that `pkgs` is defined in terms of itself, better not to think too much about
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that).
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We also use `default.nix` to load our pinned version of the `nixpkgs`
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repository. This set of packages will always be the same, independently from
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where or when you use it. The pinned version can be upgraded with the small
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`nixpkgs-upgrade` utility. Running `nixpkgs-upgrade > nix/nixpkgs-version.nix`
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in `nix-shell` will upgrade the pinned version to the latest `nixpkgs-unstable`
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version.
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### `shell.nix`
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[`shell.nix`](../shell.nix) defines an environment in which PostgREST can be
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built and developed. It extends the build enviroment from our `postgrest`
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attribute with useful utilities that will be put on the PATH in `nix-shell`.
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### `nix/overlays`
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Our overlays to the Nix package set are defined here. They allow us to tweak our
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`pkgs` in `default.nix` by adding new packages or overriding existing ones.
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