forked from mirrors/nixpkgs
bac379f30a
The nixpkgs manual contains references to both sri hash and explicit sha256 attributes. This is at best confusing to new users. Since the final destination is exclusive use of sri hashes, see nixos/rfcs#131, might as well push new users in that direction gently. Notable exceptions to sri hash support are builtins.fetchTarball, cataclysm-dda, coq, dockerTools.pullimage, elixir.override, and fetchCrate. None, other than builtins.fetchTarball, are fundamentally incompatible, but all currently accept explicit sha256 attributes as input. Because adding backwards compatibility is out of scope for this change, they have been left intact, but migration to sri format has been made for any using old hash formats. All hashes have been manually tested to be accurate, and updates were only made for missing upstream artefacts or bugs.
74 lines
2.5 KiB
Markdown
74 lines
2.5 KiB
Markdown
# Crystal {#crystal}
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## Building a Crystal package {#building-a-crystal-package}
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This section uses [Mint](https://github.com/mint-lang/mint) as an example for how to build a Crystal package.
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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. Executable projects should usually commit the `shard.lock` file, but sometimes that's not the case, which means you need to generate it yourself. With an existing `shard.lock` file, `crystal2nix` can be run.
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```bash
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$ git clone https://github.com/mint-lang/mint
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$ cd mint
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$ git checkout 0.5.0
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$ if [ ! -f shard.lock ]; then nix-shell -p shards --run "shards lock"; fi
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$ nix-shell -p crystal2nix --run crystal2nix
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```
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This should have generated a `shards.nix` file.
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Next create a Nix file for your derivation and use `pkgs.crystal.buildCrystalPackage` as follows:
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```nix
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with import <nixpkgs> {};
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crystal.buildCrystalPackage rec {
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pname = "mint";
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version = "0.5.0";
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src = fetchFromGitHub {
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owner = "mint-lang";
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repo = "mint";
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rev = version;
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hash = "sha256-dFN9l5fgrM/TtOPqlQvUYgixE4KPr629aBmkwdDoq28=";
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};
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# Insert the path to your shards.nix file here
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shardsFile = ./shards.nix;
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...
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}
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```
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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:
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```nix
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crystalBinaries.mint.src = "src/mint.cr";
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# ...
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```
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Additionally you can override the default `crystal build` options (which are currently `--release --progress --no-debug --verbose`) with
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```nix
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crystalBinaries.mint.options = [ "--release" "--verbose" ];
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```
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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:
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```nix
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with import <nixpkgs> {};
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crystal.buildCrystalPackage rec {
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version = "0.5.0";
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pname = "mint";
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src = fetchFromGitHub {
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owner = "mint-lang";
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repo = "mint";
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rev = version;
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hash = "sha256-dFN9l5fgrM/TtOPqlQvUYgixE4KPr629aBmkwdDoq28=";
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};
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shardsFile = ./shards.nix;
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crystalBinaries.mint.src = "src/mint.cr";
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buildInputs = [ openssl ];
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}
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```
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