From 578f185dafd918d79c55526fa855b0377f37d14b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
Date: Sat, 14 Dec 2024 09:44:36 +0100
Subject: [PATCH] speed up ci by splitting off eval and build

- This speeds up macOS builds from 30 minutes to 11 minutes (3x faster).
- Also improve error reporting e.g. printing out what actually failed to build.
- As a result we also no longer need swap.

(cherry picked from commit 691b1ea237427845f073fbc790f960023bacdfe9)
---
 .github/workflows/ci.yml | 28 +++++++++-------------------
 scripts/build-checks     |  6 ++++++
 2 files changed, 15 insertions(+), 19 deletions(-)
 create mode 100755 scripts/build-checks

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e9397621eac..de326ed9be6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,6 +7,14 @@ on:
 permissions: read-all
 
 jobs:
+  eval:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+    - uses: cachix/install-nix-action@v30
+    - run: nix --experimental-features 'nix-command flakes' flake show --all-systems --json
 
   tests:
     needs: [check_secrets]
@@ -31,25 +39,7 @@ jobs:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-    - if: matrix.os == 'ubuntu-latest'
-      run: |
-        free -h
-        swapon --show
-        swap=$(swapon --show --noheadings | head -n 1 | awk '{print $1}')
-        echo "Found swap: $swap"
-        sudo swapoff $swap
-        # resize it (fallocate)
-        sudo fallocate -l 10G $swap
-        sudo mkswap $swap
-        sudo swapon $swap
-        free -h
-        (
-          while sleep 60; do
-            free -h
-          done
-        ) &
-    - run: nix --experimental-features 'nix-command flakes' flake check -L
-    - run: nix --experimental-features 'nix-command flakes' flake show --all-systems --json
+    - run: scripts/build-checks
 
   # Steps to test CI automation in your own fork.
   # Cachix:
diff --git a/scripts/build-checks b/scripts/build-checks
new file mode 100755
index 00000000000..e0ee70631b5
--- /dev/null
+++ b/scripts/build-checks
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+system=$(nix eval --raw --impure --expr builtins.currentSystem)
+nix eval --json ".#checks.$system" --apply builtins.attrNames | \
+  jq -r '.[]' | \
+  xargs -P0 -I '{}' sh -c "nix build -L .#checks.$system.{} || { echo 'FAILED: \033[0;31mnix build -L .#checks.$system.{}\\033[0m'; kill 0; }"