1 files changed, 126 insertions, 0 deletions
diff --git a/nixpkgs/pkgs/build-support/rust/replace-workspace-values.py b/nixpkgs/pkgs/build-support/rust/replace-workspace-values.py
new file mode 100644
index 000000000000..003023ff2560
--- /dev/null
+++ b/nixpkgs/pkgs/build-support/rust/replace-workspace-values.py
@@ -0,0 +1,126 @@
+# This script implements the workspace inheritance mechanism described
+# here: https://doc.rust-lang.org/cargo/reference/workspaces.html#the-package-table
+#
+# Please run `mypy --strict`, `black`, and `isort --profile black` on this after editing, thanks!
+
+import sys
+from typing import Any
+
+import tomli
+import tomli_w
+
+
+def load_file(path: str) -> dict[str, Any]:
+    with open(path, "rb") as f:
+        return tomli.load(f)
+
+
+# This replicates the dependency merging logic from Cargo.
+# See `inner_dependency_inherit_with`:
+# https://github.com/rust-lang/cargo/blob/4de0094ac78743d2c8ff682489e35c8a7cafe8e4/src/cargo/util/toml/mod.rs#L982
+def replace_key(
+    workspace_manifest: dict[str, Any], table: dict[str, Any], section: str, key: str
+) -> bool:
+    if (
+        isinstance(table[key], dict)
+        and "workspace" in table[key]
+        and table[key]["workspace"] is True
+    ):
+        print("replacing " + key)
+
+        local_dep = table[key]
+        del local_dep["workspace"]
+
+        workspace_dep = workspace_manifest[section][key]
+
+        if section == "dependencies":
+            if isinstance(workspace_dep, str):
+                workspace_dep = {"version": workspace_dep}
+
+            final: dict[str, Any] = workspace_dep.copy()
+
+            merged_features = local_dep.pop("features", []) + workspace_dep.get("features", [])
+            if merged_features:
+                final["features"] = merged_features
+
+            local_default_features = local_dep.pop("default-features", None)
+            workspace_default_features = workspace_dep.get("default-features")
+
+            if not workspace_default_features and local_default_features:
+                final["default-features"] = True
+
+            optional = local_dep.pop("optional", False)
+            if optional:
+                final["optional"] = True
+
+            if local_dep:
+                raise Exception(f"Unhandled keys in inherited dependency {key}: {local_dep}")
+
+            table[key] = final
+        elif section == "package":
+            table[key] = workspace_dep
+
+        return True
+
+    return False
+
+
+def replace_dependencies(
+    workspace_manifest: dict[str, Any], root: dict[str, Any]
+) -> bool:
+    changed = False
+
+    for key in ["dependencies", "dev-dependencies", "build-dependencies"]:
+        if key in root:
+            for k in root[key].keys():
+                changed |= replace_key(workspace_manifest, root[key], "dependencies", k)
+
+    return changed
+
+
+def main() -> None:
+    top_cargo_toml = load_file(sys.argv[2])
+
+    if "workspace" not in top_cargo_toml:
+        # If top_cargo_toml is not a workspace manifest, then this script was probably
+        # ran on something that does not actually use workspace dependencies
+        print(f"{sys.argv[2]} is not a workspace manifest, doing nothing.")
+        return
+
+    crate_manifest = load_file(sys.argv[1])
+    workspace_manifest = top_cargo_toml["workspace"]
+
+    if "workspace" in crate_manifest:
+        return
+
+    changed = False
+
+    for key in crate_manifest["package"].keys():
+        changed |= replace_key(
+            workspace_manifest, crate_manifest["package"], "package", key
+        )
+
+    changed |= replace_dependencies(workspace_manifest, crate_manifest)
+
+    if "target" in crate_manifest:
+        for key in crate_manifest["target"].keys():
+            changed |= replace_dependencies(
+                workspace_manifest, crate_manifest["target"][key]
+            )
+
+    if (
+        "lints" in crate_manifest
+        and "workspace" in crate_manifest["lints"]
+        and crate_manifest["lints"]["workspace"] is True
+    ):
+        crate_manifest["lints"] = workspace_manifest["lints"]
+
+    if not changed:
+        return
+
+    with open(sys.argv[1], "wb") as f:
+        tomli_w.dump(crate_manifest, f)
+
+
+if __name__ == "__main__":
+    main()