From c8439e437c3f595273cd3eb5b20215b535ec19da Mon Sep 17 00:00:00 2001 From: Wolfgang Walther Date: Mon, 27 Apr 2026 13:08:41 +0200 Subject: [PATCH] ci: use nix-build-uncached to save useless downloads There is no point to actually realize the derivations to disk, when they are in cache. `nix-build-uncached` checks the cache and stops before downloading dependencies if they are available. It will however build as normal on a cache-miss. Should speed up CI when no Nix dependencies change a fair bit. We can only do this for the MacOS job, which only tests the builds. We can not do this for other jobs which require the build results to be present before uploading parts of them as artifacts. --- .github/workflows/build.yaml | 16 ++++------------ default.nix | 3 +++ 2 files changed, 7 insertions(+), 12 deletions(-) diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml index 585f327d3..48f173c83 100644 --- a/.github/workflows/build.yaml +++ b/.github/workflows/build.yaml @@ -78,19 +78,11 @@ jobs: uses: ./.github/actions/setup-nix with: authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}' - - name: Install gnu sed - run: brew install gnu-sed + - name: Install nix-build-uncached + run: nix-env -f default.nix -iA nix-build-uncached - - name: Build everything - run: | - # The --dry-run will give us a list of derivations to download from cachix and - # derivations to build. We only take those that would have to be built and then build - # those explicitly. This has the advantage that pure verification will not include - # a download anymore, making it much faster. If something needs to be built, only - # the dependencies required to do so will be downloaded, but not everything. - nix-build --dry-run 2>&1 \ - | gsed -e '1,/derivations will be built:$/d' -e '/paths will be fetched/Q' \ - | xargs nix-build + - name: Build everything (default.nix) + run: nix-build-uncached stack: diff --git a/default.nix b/default.nix index f19279232..859c3ebb4 100644 --- a/default.nix +++ b/default.nix @@ -107,6 +107,9 @@ rec { inherit (pkgs.haskell.packages."${compiler}") ghcWithPackages; }; + # Used by CI on MacOS + inherit (pkgs) nix-build-uncached; + ### Tools cabalTools =