fix(rust): add rust standard library deps to the environment when the toolchain needs it

This is a fix for "error: no matching package named
`rustc-literal-escaper` found" when adding "rust-src" to the components
array in the toolchain file

rust/default.nix

@@ -25,20 +25,39 @@
       }: let
         cfg = config.krantz.rust;
 
-        src = cfg.srcFiltered;
-        manifest = (lib.importTOML "${src}/Cargo.toml").package;
+        manifest = (lib.importTOML "${cfg.srcFiltered}/Cargo.toml").package;
 
         craneLib =
-          if cfg.srcToolchain != null && builtins.pathExists cfg.srcToolchain
-          then
-            (inputs.crane.mkLib (pkgs.extend inputs.rust-overlay.overlays.default)).overrideToolchain (
-              p: p.rust-bin.fromRustupToolchainFile cfg.srcToolchain
-            )
+          if hasToolchain
+          then (inputs.crane.mkLib rustPkgs).overrideToolchain mkRustToolchain
           else inputs.crane.mkLib pkgs;
 
+        # Attrs to be included for all crane functions that build our crate
+        cargoBuildAttrs = let
+          # Include the standard library Cargo.lock if we have the "rust-src" component in our toolchain
+          cargoVendorDir =
+            lib.optionalAttrs (
+              hasToolchain
+              && lib.pipe cfg.srcToolchain [
+                builtins.readFile
+                fromTOML
+                (t: t ? toolchain.components && builtins.elem "rust-src" t.toolchain.components)
+              ]
+            ) {
+              cargoVendorDir = craneLib.vendorMultipleCargoDeps {
+                inherit (craneLib.findCargoFiles cfg.srcFiltered) cargoConfigs;
+                cargoLockList = [
+                  "${cfg.srcFiltered}/Cargo.lock"
+                  "${(mkRustToolchain rustPkgs).passthru.availableComponents.rust-src}/lib/rustlib/src/rust/library/Cargo.lock"
+                ];
+              };
+            };
+        in
+          rec {
+            src = cfg.srcFiltered;
+
             buildInputs = cfg.runtimeDeps;
 
-        # build dependencies
             nativeBuildInputs = cfg.buildDeps;
 
             # Build *just* the cargo dependencies, so we can reuse
@@ -46,7 +65,14 @@
             cargoArtifacts = craneLib.buildDepsOnly ({
                 inherit src buildInputs nativeBuildInputs;
               }
+              // cargoVendorDir
               // cfg.cargoArtifacts.extraAttrs);
+          }
+          // cargoVendorDir;
+
+        hasToolchain = cfg.srcToolchain != null && builtins.pathExists cfg.srcToolchain;
+        rustPkgs = pkgs.extend inputs.rust-overlay.overlays.default;
+        mkRustToolchain = p: p.rust-bin.fromRustupToolchainFile cfg.srcToolchain;
       in {
         options.krantz.rust = {
           enable = lib.mkEnableOption "building a cargo project with crane";
@@ -206,8 +232,8 @@
           # Accessible through 'nix build', 'nix shell', 'nix run', etc
           packages = lib.mkIf cfg.package.enable {
             ${cfg.package.name} = craneLib.buildPackage ({
-                inherit src buildInputs nativeBuildInputs cargoArtifacts;
               }
+              // cargoBuildAttrs
               // cfg.package.extraAttrs);
           };
 
@@ -224,10 +250,10 @@
           };
 
           checks = lib.mkIf cfg.checks.enable {
-            clippy = lib.mkIf cfg.checks.linter (craneLib.cargoClippy {
-              inherit src buildInputs nativeBuildInputs cargoArtifacts;
+            clippy = lib.mkIf cfg.checks.linter (craneLib.cargoClippy ({
                 cargoClippyExtraArgs = "-- --deny warnings";
-            });
+              }
+              // cargoBuildAttrs));
           };
         };
       });