feat: populate meta.description from Cargo.toml

CHANGELOG.md

@@ -6,6 +6,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## Unreleased
 
+### Added
+* `craneLib.buildPackage` and `craneLib.buildTrunkPackage` now populate the
+  derivation's `meta.description` from the crate's `package.description` (or
+  `workspace.package.description`) in its root Cargo.toml, unless
+  `meta.description` is explicitly set. `crateNameFromCargoToml`
+  correspondingly exposes a `description` attribute (omitted when absent).
+
 ## [0.24.0] - 2026-08-21
 
 ### Changed

docs/API.md

@@ -898,7 +898,7 @@ raised during evaluation.
 
 `crateNameFromCargoToml :: set -> set`
 
-Extract a crate's name and version from its Cargo.toml file.
+Extract a crate's name, version, and description from its Cargo.toml file.
 
 The resulting `pname` attribute will be populated with the value of the
 Cargo.toml's (top-level) attributes in the following order, where the first
@@ -916,14 +916,21 @@ attribute (with a string value) will be chosen:
 1. `workspace.package.version`
 1. Otherwise a placeholder version will be used
 
+The resulting `description` attribute will be populated from
+`package.description` (or `workspace.package.description`), and simply omitted
+when neither is present (there is no placeholder fallback).
+
 Note that *only the root `Cargo.toml` of the specified source will be checked*.
 Directories **will not be crawled** to resolve potential workspace inheritance.
 
 ```nix
 craneLib.crateNameFromCargoToml { cargoToml = ./Cargo.toml; }
-# { pname = "simple"; version = "0.1.0"; }
+# { pname = "simple"; version = "0.1.0"; description = "..."; }
 ```
 
+`craneLib.buildPackage` and `craneLib.buildTrunkPackage` also populate
+`meta.description` from this value unless explicitly set.
+
 ### `craneLib.crateRegistries`
 
 `crateRegistries :: set`

lib/buildPackage.nix

@@ -98,6 +98,10 @@ mkCargoDerivation (
         fi
       '';
 
+    meta =
+      lib.optionalAttrs (crateName ? description) { inherit (crateName) description; }
+      // (args.meta or { });
+
     nativeBuildInputs = (args.nativeBuildInputs or [ ]) ++ [
       # NB: avoid adding any non-hook packages here. Doing so will end up
       # changing PKG_CONFIG_PATH and cause rebuilds of `*-sys` crates.

lib/buildTrunkPackage.nix

@@ -109,6 +109,10 @@ mkCargoDerivation (
         cp -r "$(dirname "${trunkIndexPath}")/dist" $out
       '';
 
+    meta =
+      lib.optionalAttrs (crateName ? description) { inherit (crateName) description; }
+      // (args.meta or { });
+
     # Installing artifacts on a distributable dir does not make much sense
     doInstallCargoArtifacts = args.doInstallCargoArtifacts or false;
 

lib/crateNameFromCargoToml.nix

@@ -59,7 +59,7 @@ let
 
   internalName = internalCrateNameFromCargoToml toml debugPath;
 in
-{
+lib.filterAttrs (_: v: v != null) {
   pname =
     internalName.pname or (traceMsg "name" "pname" "cargo-package" [
       ''`package.metadata.crane.name` = "..."''
@@ -69,4 +69,5 @@ in
     internalName.version or (traceMsg "version" "version" "0.0.1" [
       ''`workspace.package.version` = "..."''
     ]);
+  description = internalName.description or null;
 }

lib/internalCrateNameFromCargoToml.nix

@@ -37,4 +37,8 @@ lib.filterAttrs (_: v: v != null) {
     (toml.package.version or null)
     (toml.workspace.package.version or null)
   ];
+  description = firstNonNull [
+    (toml.package.description or null)
+    (toml.workspace.package.description or null)
+  ];
 }