Add fallback for rust without profile support

flake.nix

@@ -143,6 +143,10 @@
  targets = [ "wasm32-unknown-unknown" "aarch64-unknown-linux-gnu" ];
  });
 
+ rustup-toolchain-profile-missing = assertEq (builtins.tryEval (fromRustupToolchain { channel = "1.51.0"; profile = "non_existent"; })).success false;
+ rustup-toolchain-profile-too-early = assertEq (builtins.tryEval (fromRustupToolchain { channel = "1.29.0"; profile = "minimal"; })).success false;
+ rustup-toolchain-profile-fallback = assertEq (fromRustupToolchain { channel = "1.29.0"; }) stable."1.29.0".rust;
+
  rustup-toolchain-file-toml = assertEq
  (fromRustupToolchainFile ./tests/rust-toolchain-toml)
  (nightly."2021-03-25".default.override {

rust-overlay.nix

@@ -48,11 +48,25 @@ let
  # Select a toolchain and aggregate components by rustup's `rust-toolchain` file format.
  # See: https://rust-lang.github.io/rustup/concepts/profiles.html
  # Or see source: https://github.com/rust-lang/rustup/blob/84974df1387812269c7b29fa5f3bb1c6480a6500/doc/src/overrides.md#the-toolchain-file
- fromRustupToolchain = { path ? null, channel ? null, components ? [], targets ? [], profile ? "default" }:
+ fromRustupToolchain = { path ? null, channel ? null, profile ? null, components ? [], targets ? [] }:
  if path != null then throw "`path` is not supported, please directly add it to your PATH instead"
  else if channel == null then throw "`channel` is required"
  else
- (toolchainFromManifest (selectManifest { inherit channel; }))._profiles.${profile}.override {
+ let
+ toolchain = toolchainFromManifest (selectManifest { inherit channel; });
+ profile' = if profile == null then "default" else profile;
+ pkg =
+ if toolchain._profiles != {} then
+ toolchain._profiles.${profile'} or (throw ''
+ Rust ${toolchain._version} doesn't have profile `${profile'}`.
+ Available profiles are: ${self.lib.concatStringsSep ", " (builtins.attrNames toolchain._profiles)}
+ '')
+ # Fallback to package `rust` when profiles are not supported and not specified.
+ else if profile == null then
+ toolchain.rust
+ else
+ throw "Cannot select profile `${profile'}` since rust ${toolchain._version} is too early to support profiles";
+ in pkg.override {
  extensions = components;
  inherit targets;
  };
@@ -468,9 +482,8 @@ let
 
  # Internal use.
  _components = componentSet;
- _profiles = if profiles == {}
- then throw "Rust ${manifest.version} doesn't support profiles"
- else profiles;
+ _profiles = profiles;
+ _version = manifest.version;
  };
 
  # Same as `toolchainFromManifest` but read from a manifest file.