Write a `main.rs` to `src/bin/dummy` within the generated dummy source,
rather than `src/main.rs` to account for `illegalBin` test case
Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>
* mkDummySrc: also include `no_std` attrs for target_os = uefi
* buildDepsOnly: only check with `--all-targets` if doCheck enabled
* mkDummySrc: allow customizing dummy Rust file contents
* Instead of injecting our own dummy `build.rs` file, we will patch the
`Cargo.toml` files to specify a build script in the Nix store
* This allow cargo to notice the difference (i.e. changed build script
path) where it could not before (due to nix enforcing that all sources
always have the same timestamp)
when trying to use crane with a non local src (eg, not `./.`) we get the error
```
$ nix flake show
<...>
error: access to absolute path '/Cargo.toml' is forbidden in pure eval mode (use '--impure' to override)
(use '--show-trace' to show detailed location information)
```
To fix this, we quote the relative paths so to properly append them to the base path.
https://nixos.wiki/wiki/Nix_Expression_Language#Coercing_a_relative_path_with_interpolated_variables_to_an_absolute_path_.28for_imports.29
## Reproduction flake
```
{
description = "Build a cargo project without extra checks";
inputs = {
nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
crane = {
url = "github:ipetkov/crane";
inputs.nixpkgs.follows = "nixpkgs";
};
external-crate-source = {
url = "github:ray-kast/empress";
flake = false;
};
flake-utils.url = "github:numtide/flake-utils";
};
outputs = { self, nixpkgs, crane, flake-utils, external-crate-source, ... }:
flake-utils.lib.eachDefaultSystem (system:
let
pkgs = nixpkgs.legacyPackages.${system};
test-crate = crane.lib.${system}.buildPackage {
src = external-crate-source.outPath;
};
in
{
packages.default = test-crate;
});
}
```
* Seems like cachix is still pushing the results up to the cache, we
might as well get use of downloading the (empty) results rather than
having to pull down the intermediary binaries and running them each
time
* There are some edge cases where cargo will allow a lib.rs file to be
present but not a main.rs (e.g. a binary cannot be called "examples",
which will happen if the crate is called that and a main.rs file is
present)
