buildRustCrate: support propagatedBuildInputs in crate overrides (#503956)

pkgs/build-support/rust/build-rust-crate/default.nix

@@ -325,6 +325,7 @@ lib.makeOverridable
       buildDependencies_ = buildDependencies;
       processedAttrs = [
         "src"
+        "propagatedBuildInputs"
         "nativeBuildInputs"
         "buildInputs"
         "crateBin"
@@ -418,7 +419,8 @@ lib.makeOverridable
         buildInputs =
           lib.optionals stdenv.hostPlatform.isDarwin [ libiconv ]
           ++ (crate.buildInputs or [ ])
-          ++ buildInputs_;
+          ++ buildInputs_
+          ++ completePropagatedBuildInputs;
         dependencies = map lib.getLib dependencies_;
         buildDependencies = map lib.getLib buildDependencies_;
 
@@ -428,6 +430,16 @@ lib.makeOverridable
           ++ lib.concatMap (dep: dep.completeBuildDeps ++ dep.completeDeps) buildDependencies
         );
 
+        # Propagated native build inputs from this crate and all transitive Rust
+        # dependencies. Analogous to completeDeps but for native library deps:
+        # a crate can declare `propagatedBuildInputs` in its override and they
+        # will automatically be added to the buildInputs of every crate that
+        # depends on it, without having to repeat them up the dependency tree.
+        completePropagatedBuildInputs = lib.unique (
+          (crate.propagatedBuildInputs or [ ])
+          ++ lib.concatMap (dep: dep.completePropagatedBuildInputs or [ ]) dependencies
+        );
+
         # Create a list of features that are enabled by the crate itself and
         # through the features argument of buildRustCrate. Exclude features
         # with a forward slash, since they are passed through to dependencies,

pkgs/build-support/rust/build-rust-crate/test/default.nix

@@ -1060,6 +1060,69 @@ rec {
                 test -x '${pkg}/bin/rcgen' && touch $out
               ''
           );
+
+      # Test that propagatedBuildInputs declared in a crate override are
+      # collected by completePropagatedBuildInputs and propagate transitively
+      # to all crates that depend on it.
+      propagatedBuildInputsTest =
+        let
+          fakeNativeLib = runCommand "fake-native-lib" { } "mkdir -p $out/lib && touch $out/lib/libfoo.a";
+
+          # Library crate that declares a native dep via propagatedBuildInputs
+          libCrate = mkHostCrate {
+            crateName = "mylib";
+            src = mkLib "src/lib.rs";
+            propagatedBuildInputs = [ fakeNativeLib ];
+          };
+
+          # Binary crate with a direct dependency on libCrate
+          binCrate = mkHostCrate {
+            crateName = "mybin";
+            src = mkFile "src/main.rs" "fn main() {}";
+            dependencies = [ libCrate ];
+          };
+
+          # Intermediate library that depends on libCrate
+          transitiveLib = mkHostCrate {
+            crateName = "transitivelib";
+            src = mkLib "src/lib.rs";
+            dependencies = [ libCrate ];
+          };
+
+          # Binary crate that only depends on transitiveLib (not libCrate directly)
+          transitiveBin = mkHostCrate {
+            crateName = "transitivebin";
+            src = mkFile "src/main.rs" "fn main() {}";
+            dependencies = [ transitiveLib ];
+          };
+        in
+        runCommand "propagated-build-inputs-test"
+          {
+            libCrateInputs = libCrate.completePropagatedBuildInputs;
+            binCrateInputs = binCrate.completePropagatedBuildInputs;
+            transitiveBinInputs = transitiveBin.completePropagatedBuildInputs;
+          }
+          ''
+            # libCrate itself should have fakeNativeLib in completePropagatedBuildInputs
+            echo "$libCrateInputs" | grep -q "${fakeNativeLib}" || {
+              echo "ERROR: fakeNativeLib not in libCrate.completePropagatedBuildInputs"
+              exit 1
+            }
+
+            # binCrate depends on libCrate, so fakeNativeLib should propagate
+            echo "$binCrateInputs" | grep -q "${fakeNativeLib}" || {
+              echo "ERROR: fakeNativeLib not propagated to binCrate.completePropagatedBuildInputs"
+              exit 1
+            }
+
+            # transitiveBin → transitiveLib → libCrate: fakeNativeLib should propagate transitively
+            echo "$transitiveBinInputs" | grep -q "${fakeNativeLib}" || {
+              echo "ERROR: fakeNativeLib not transitively propagated to transitiveBin.completePropagatedBuildInputs"
+              exit 1
+            }
+
+            touch $out
+          '';
     }
   );
   test = releaseTools.aggregate {