Remo RechkemmerandGitHub
48c9ac36b1
* Refactor tests and fix README * fix linting hints from new hlint version * postgrest-style with new nixpkgs-fmt
179 lines
6.1 KiB
Markdown
179 lines
6.1 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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We recommend that you use the PostgREST binary cache on
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[cachix](https://cachix.org/):
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```
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# Install cachix:
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nix-env -iA cachix -f https://cachix.org/api/v1/install
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# Set cachix up to use the PostgREST binary cache:
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cachix use postgrest
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```
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Without cachix, your machine will have to rebuild all the dependencies that are
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derived on top of `Musl` for the static builds, which can take a very long time.
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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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## Aside: Working with `nix-shell` and the PostgREST utility scripts
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The PostgREST utilities available in `nix-shell` all have names that begin with
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`postgrest-`, so you can use tab completion (typing `postgrest-` and pressing
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`<tab>`) in `nix-shell` to see all that are available:
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```
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# Note: The utilities listed here might not be up to date.
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[nix-shell]$ postgrest-<tab>
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postgrest-lint postgrest-test-spec-postgresql-10
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postgrest-style postgrest-test-spec-postgresql-11
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postgrest-style-check postgrest-test-spec-postgresql-12
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postgrest-test-all postgrest-test-spec-postgresql-9.4
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postgrest-test-spec postgrest-test-spec-postgresql-9.5
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postgrest-test-spec-all postgrest-test-spec-postgresql-9.6
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[nix-shell]$
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```
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To run one-off commands, you can also use `nix-shell --run <command>`, which
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will lauch the Nix shell, run that one command and exit. Note that the tab
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completion will not work with `nix-shell --run`, as Nix has yet to evaluate
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our Nix expressions to see which utilities are available.
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```
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$ nix-shell --run postgrest-style
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# Note that you need to quote any arguments that you would like to pass to
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# the command to be run in nix-shell:
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$ nix-shell --run "postgrest-foo --bar"
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```
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A third option is to install utilities that you use very often locally:
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```
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$ nix-env -f default.nix -iA style
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# `postgrest-style` can now be run directly:
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$ postgrest-style
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```
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Note that this does not yet work for all utilities (e.g. `postgrest-test-spec` currently
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needs to be run within the Nix shell environment).
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If you use `nix-shell` very often, you might like to use https://github.com/xzfc/cached-nix-shell,
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which skips evaluating all our Nix expressions if nothing changed, reducing startup time for the
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shell considerably.
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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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