nixpkgs/doc/languages-frameworks/crystal.section.md
Ryan Mulligan b8344f9e5c doc: explicit Markdown anchors for top-level headings; remove metadata
I used the existing anchors generated by Docbook, so the anchor part
should be a no-op. This could be useful depending on the
infrastructure we choose to use, and it is better to be explicit than
rely on Docbook's id generating algorithms.

I got rid of the metadata segments of the Markdown files, because they
are outdated, inaccurate, and could make people less willing to change
them without speaking with the author.
2021-01-01 10:02:57 -08:00

72 lines
2.2 KiB
Markdown

# Crystal {#crystal}
## Building a Crystal package
This section uses [Mint](https://github.com/mint-lang/mint) as an example for how to build a Crystal package.
If the Crystal project has any dependencies, the first step is to get a `shards.nix` file encoding those. Get a copy of the project and go to its root directory such that its `shard.lock` file is in the current directory, then run `crystal2nix` in it
```bash
$ git clone https://github.com/mint-lang/mint
$ cd mint
$ git checkout 0.5.0
$ nix-shell -p crystal2nix --run crystal2nix
```
This should have generated a `shards.nix` file.
Next create a Nix file for your derivation and use `pkgs.crystal.buildCrystalPackage` as follows:
```nix
with import <nixpkgs> {};
crystal.buildCrystalPackage rec {
pname = "mint";
version = "0.5.0";
src = fetchFromGitHub {
owner = "mint-lang";
repo = "mint";
rev = version;
sha256 = "0vxbx38c390rd2ysvbwgh89v2232sh5rbsp3nk9wzb70jybpslvl";
};
# Insert the path to your shards.nix file here
shardsFile = ./shards.nix;
...
}
```
This won't build anything yet, because we haven't told it what files build. We can specify a mapping from binary names to source files with the `crystalBinaries` attribute. The project's compilation instructions should show this. For Mint, the binary is called "mint", which is compiled from the source file `src/mint.cr`, so we'll specify this as follows:
```nix
crystalBinaries.mint.src = "src/mint.cr";
# ...
```
Additionally you can override the default `crystal build` options (which are currently `--release --progress --no-debug --verbose`) with
```nix
crystalBinaries.mint.options = [ "--release" "--verbose" ];
```
Depending on the project, you might need additional steps to get it to compile successfully. In Mint's case, we need to link against openssl, so in the end the Nix file looks as follows:
```nix
with import <nixpkgs> {};
crystal.buildCrystalPackage rec {
version = "0.5.0";
pname = "mint";
src = fetchFromGitHub {
owner = "mint-lang";
repo = "mint";
rev = version;
sha256 = "0vxbx38c390rd2ysvbwgh89v2232sh5rbsp3nk9wzb70jybpslvl";
};
shardsFile = ./shards.nix;
crystalBinaries.mint.src = "src/mint.cr";
buildInputs = [ openssl ];
}
```