a572f8e23d
i always seem to get this wrong Change-Id: Ib6f31523aba1d9f9a32d9af95b96b8d75e0ec16e Reviewed-on: https://cl.tvl.fyi/c/depot/+/6863 Reviewed-by: wpcarro <wpcarro@gmail.com> Autosubmit: wpcarro <wpcarro@gmail.com> Tested-by: BuildkiteCI
50 lines
1.6 KiB
Markdown
50 lines
1.6 KiB
Markdown
## Background
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I rarely use `nix-shell` for its originally intended purpose of "reproducing the
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environment of a derivation for development". Instead, I often use it to put
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some executable on my `PATH` for some ad hoc task.
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What's `nix-shell`'s "intended purpose"? Let's ask The Man (`man nix-shell`):
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> The command nix-shell will build the dependencies of the specified derivation,
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> but not the derivation itself. It will then start an interactive shell in
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> which all environment variables defined by the derivation path have been set
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> to their corresponding values, and the script $stdenv/setup has been
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> sourced. This is useful for reproducing the environment of a derivation for
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> development.
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Because I'm abusing `nix-shell` in this way, I'm liable to forget that
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`nix-shell` puts `buildInputs` on `PATH` and *not* the derivation itself. But I
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often only want the derivation!
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## Solution
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Pass the Nix expression to `nix-shell -p`:
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```shell
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λ nix-shell -p '(import /depot {}).tvix.eval'
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```
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## Explanation
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This works because Nix forwards the arguments passed to `-p` (i.e. `--packages`)
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and interpolates them into this expression here: [source][nix-src]
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```nix
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{ ... }@args:
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with import <nixpkgs> args;
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(pkgs.runCommandCC or pkgs.runCommand) "shell" {
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buildInputs = [
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# --packages go here
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];
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}
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```
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So really you can pass-in *any* valid Nix expression that produces a derivation
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and `nix-shell` will put its outputs on your `PATH`.
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Enjoy!
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[nix-src]: https://sourcegraph.com/github.com/NixOS/nix@3ae9467d57188f9db41f85b0e5c41c0c9d141955/-/blob/src/nix-build/nix-build.cc?L266
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