types: remove Path* typedefs by amaanq · Pull Request #15354 · NixOS/nix

amaanq · 2026-02-26T20:15:59Z

Motivation

We want to get rid of the unnecessary Path* typedefs. This commit replaces all usages with their underlying types, that being std::string for store paths, std::filesystem::path for filesystem paths, StringSet for path sets, and std::string_view` for non-owning references.

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src/libutil/include/nix/util/file-path.hh

src/libexpr/include/nix/expr/eval-settings.hh

src/libexpr/parser.y

src/libfetchers/git.cc

src/libflake/include/nix/flake/flakeref.hh

src/libstore-tests/derivation/external-formats.cc

src/libstore/build/derivation-check.cc

src/libstore/builtins/buildenv.cc

src/libstore/gc.cc

src/libstore/globals.cc

src/libstore/include/nix/store/derivations.hh

src/libstore/include/nix/store/local-settings.hh

src/libstore/include/nix/store/local-store.hh

src/libstore/include/nix/store/store-api.hh

src/libstore/include/nix/store/store-dir-config.hh

src/libutil/configuration.cc

src/libutil/include/nix/util/file-path.hh

src/libutil/windows/file-path.cc

src/nix/nix-copy-closure/nix-copy-closure.cc

src/nix/nix-store/nix-store.cc

src/libstore/include/nix/store/store-api.hh

src/libutil/include/nix/util/configuration.hh

src/nix/nix-store/nix-store.cc

src/libutil/configuration.cc

src/libutil/include/nix/util/configuration.hh

src/libutil/include/nix/util/file-path.hh

src/nix/nix-copy-closure/nix-copy-closure.cc

This commit replaces all usages with their underlying types, that being `std::string` for store paths, `std::filesystem::path` for filesystem paths, `StringSet` for path sets, and `std::string_view` for non-owning references.

xokdvium · 2026-02-27T11:05:21Z

src/libutil/include/nix/util/configuration.hh

+struct AbsolutePath : std::filesystem::path
+{
+    using path::path;
+    using path::operator=;
+
+    AbsolutePath(const std::filesystem::path & p)


We should be careful to avoid slicing here. Maybe a better pattern would be private inheritance and using all necessary methods?

It could just be a wrapper type with a single std::filesystem::path field. That is easy to reason about for any C++ noobs :).

xokdvium · 2026-02-27T11:07:51Z

src/libstore/local-store.cc

    return bd.has_value()               ? *bd
           : buildDir.get().has_value() ? *buildDir.get()
-                                        : std::filesystem::path{stateDir.get()} / "builds";
+                                        : AbsolutePath{stateDir.get() / "builds"};


This does slicing, not good

Wrapper type would instead have it take ownership, seems good.

amaanq requested review from Ericson2314 and edolstra as code owners February 26, 2026 20:16

github-actions bot added new-cli Relating to the "nix" command store Issues and pull requests concerning the Nix store fetching Networking with the outside (non-Nix) world, input locking c api Nix as a C library with a stable interface labels Feb 26, 2026

amaanq force-pushed the convert-path-setting branch from 0a1be0d to f10346c Compare February 26, 2026 20:18