Prefer profiles for stable toolchains

Author: oxalica

README.md

@@ -22,7 +22,7 @@ You can put the code below into your `~/.config/nixpkgs/overlays.nix`.
 ```
 Then the provided attribute paths are available in nix command.
 ```bash
-$ nix-env -iA rust-bin.stable.latest.rust # Do anything you like.
+$ nix-env -iA rust-bin.stable.latest.default # Do anything you like.
 ```
 
 Alternatively, you can install it into nix channels.
@@ -68,7 +68,7 @@ Here's an example of using it in nixos configuration.
           ./configuration.nix # Your system configuration.
           ({ pkgs, ... }: {
             nixpkgs.overlays = [ rust-overlay.overlay ];
-            environment.systemPackages = [ pkgs.rust-bin.stable.latest.rust ];
+            environment.systemPackages = [ pkgs.rust-bin.stable.latest.default ];
           })
         ];
       };
@@ -164,18 +164,16 @@ Some examples (assume `nixpkgs` had the overlay applied):
   You can check availability on [Rustup packages availibility](https://rust-lang.github.io/rustup-components-history/).
 
 - A specific version of stable rust:
-  `nixpkgs.rust-bin.stable."1.48.0".rust`
+  `nixpkgs.rust-bin.stable."1.48.0".default`
 - A specific date of beta rust:
-  `nixpkgs.rust-bin.nightly."2021-01-01".rust`
-- A specific version of stable rust:
-  `nixpkgs.rust-bin.stable."1.48.0".rust`
+  `nixpkgs.rust-bin.beta."2021-01-01".default`
 - A specific date of nightly rust:
-  `nixpkgs.rust-bin.nightly."2020-12-31".rust`
+  `nixpkgs.rust-bin.nightly."2020-12-31".default`
 - Latest stable rust with additional component `rust-src` and extra target
   `arm-unknown-linux-gnueabihf`:
 
   ```nix
-  nixpkgs.rust-bin.stable.latest.rust.override {
+  nixpkgs.rust-bin.stable.latest.default.override {
     extensions = [ "rust-src" ];
     targets = [ "arm-unknown-linux-gnueabihf" ];
   }

rust-overlay.nix

@@ -454,7 +454,16 @@ let
     {
       # Legacy support for special pre-aggregated package.
       # It has more components than `default` profile but less than `complete` profile.
-      rust = mkPackage "rust" manifest.pkg.rust;
+      rust =
+        let pkg = mkPackage "rust" manifest.pkg.rust; in
+        if builtins.match ".*[.].*[.].*" != null
+          then builtins.trace ''
+            Rust ${manifest.version}:
+            Pre-aggregated package `rust` is not encouraged for stable channel since it contains almost all and uncertain components.
+            Consider use `default` profile like `rust-bin.stable.latest.default` and override it with extensions you need.
+            See README for more information.
+          '' pkg
+          else pkg;
 
       # Internal use.
       _components = componentSet;