Rework diff-hosts

Now it'll detect wether there are changes to a hosts closure at all,
lists build failures as such and is able to handle newly added or
removed hosts.

.github/scripts/diff-hosts.sh

@@ -0,0 +1,112 @@
+#!/usr/bin/env bash
+
+# host_exists(flake, host)
+# Checks if ${flake}#nixosConfigurations.$host
+# Returns 0 if it does, 1 if it does not
+function host_exists() {
+    local cmd="nix eval $1#nixosConfigurations --apply 'builtins.hasAttr \"$2\"'"
+    # echo "$cmd"
+    has_host=$(eval "$cmd")
+    if [[ $has_host == "true" ]]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+# get_hosts(flake, available_hosts)
+# Store a list of all available hosts in flake to $available_hosts
+function get_hosts() {
+    local -n hosts=$2
+    IFS=" " read -r -a hosts <<< "$(nix eval $1#nixosConfigurations --raw --apply 'x: builtins.concatStringsSep " " (builtins.attrNames x)')"
+}
+
+set -o errexit
+# When using to check local changes, the step summary is not needed
+step_summary="${GITHUB_STEP_SUMMARY-/dev/null}"
+
+before_ref="${GITHUB_BASE_REF-main}"
+before_ref="origin/${before_ref/#refs\/heads\//}"
+if [[ $GITHUB_REF == "target/refs/main" ]]; then
+    # If triggered on main, compare with the previous commit
+    before_ref="$(git log  HEAD~1 -1 --format=format:"%H")"
+fi
+
+before_rev="$(git rev-parse "$before_ref")"
+before_rev_abbr="$before_ref"
+before_flake="git+file:.?ref=${before_rev}"
+
+after_rev="$(git rev-parse --verify HEAD)"
+after_rev_abbr="$(git rev-parse --abbrev-ref HEAD)"
+if [[ -z $(git status --short) ]]; then
+    # If the working tree is clean, we can use the latest commit hash directly
+    # and thus profit from even more reduced build times
+    after_flake="git+file:.?ref=${after_rev}"
+else
+    # That way the script can be used to check local (non commited) changes
+    after_flake="."
+fi
+
+before_hosts=()
+get_hosts "$before_flake" before_hosts
+after_hosts=()
+get_hosts "$after_flake" after_hosts
+all_hosts=( "${before_hosts[@]}" "${after_hosts[@]}" )
+
+# Unite both arrays
+# From https://stackoverflow.com/a/33153989
+declare -A _all_hosts
+for k in "${all_hosts[@]}"; do _all_hosts["$k"]=1; done
+all_hosts=("${!_all_hosts[@]}")
+
+echo -e "## Closure differences\n" >> "$step_summary"
+dirty=""
+if [[ -n $(git status --short) ]]; then
+    dirty="-DIRTY"
+fi
+echo -e "_Comparing prior $before_rev_abbr ([$before_rev]) with current $after_rev_abbr ([$after_rev]$dirty)_\n" | tee -a "$step_summary"
+repo_url="${GITHUB_SERVER_URL}/$GITHUB_REPOSITORY"
+{
+    echo "[$before_rev]: $repo_url/commit/$before_rev";
+    echo "[$after_rev]: $repo_url/commit/$after_rev";
+} >> "$step_summary"
+
+
+for host in "${all_hosts[@]}"; do
+    host_exists "$before_flake" "$host" && a_exists=true || a_exists=false
+    host_exists "$after_flake" "$host" && b_exists=true || b_exists=false
+    if $a_exists && ! $b_exists; then
+        echo -e "**${host}** was removed\n" | tee -a "$step_summary"
+    elif ! $a_exists && $b_exists; then
+        echo -e "**${host}** was added\n" | tee -a "$step_summary"
+    else
+        echo "::group::Diff-closures for ${host}"
+        drv="nixosConfigurations.$host.config.system.build.toplevel"
+        diff_cmd="nix store diff-closures ${before_flake}#${drv} ${after_flake}#${drv}"
+        # Initially build host so that we don't spam the log
+        change_lines=$($diff_cmd 2>&1 | wc -l)
+        # Run once so that we have the colorful output in the github actions log
+        $diff_cmd && build_ok=true || build_ok=false
+        if [[ $change_lines -gt 0 ]] || [[ ! $build_ok ]]; then
+            if $build_ok; then
+                echo "ok"
+                echo "${host} changed"
+                echo -e "<details>\n<summary><b>${host}</b> changed</summary>\n\n" >> "$step_summary"
+            else
+                echo "${host} failed to build"
+                echo -e "<details>\n<summary><b>${host}</b> failed to build</summary>\n\n" >> "$step_summary"
+            fi
+
+            {
+                echo '```';
+                $diff_cmd --show-trace | sed -e 's/\x1b\[[0-9;]*m//g';
+                echo '```';
+                echo -e "\n</details>\n";
+            } >> "$step_summary" 2>&1
+        else
+            echo -e "**${host}** has not changed\n" | tee -a "$step_summary"
+        fi
+
+        echo "::endgroup::"
+    fi
+done

.github/workflows/build-systems.yaml

@@ -26,6 +26,7 @@ jobs:
         echo Discovered the following system configs
         nix flake show . --json | jq ".nixosConfigurations|keys[]" -r
     - name: Build systems
+      id: build
       run: |
         echo "## Builds succeeded" >> $GITHUB_STEP_SUMMARY
         echo "" >> $GITHUB_STEP_SUMMARY
@@ -43,29 +44,6 @@ jobs:
           echo "| ${host} | \`${out_path}\` |" >> $GITHUB_STEP_SUMMARY
         done
     - name: Diff closures
-      # Since this is only triggered by pushes to main, no need to compare to main for pushes
+      # Still would like to see the changes for the non-failing hosts
-      if: github.event_name != 'push'
+      if: ${{ success() }} || ${{ failure() }}
-      run: |
+      run: ./.github/scripts/diff-hosts.sh
-        # Compare to pull_request_target or, if this has no PR-Target, main
-        target_ref="${GITHUB_BASE_REF-main}"
-        target_ref="origin/${target_ref/#refs\/heads\//}"
-        if [[ $GITHUB_REF == "target/refs/main" ]]; then
-          # If triggered on main, compare with the previous commit
-          target_ref="$(git log  HEAD~1 -1 --format=format:"%H")"
-        fi
-        echo -e "## Closure differences\n" >> $GITHUB_STEP_SUMMARY
-        echo "_Comparing current $(git rev-parse --abbrev-ref HEAD) ($(git rev-parse --verify HEAD)) to ${target_ref} ($(git rev-parse $target_ref))_" | tee -a $GITHUB_STEP_SUMMARY
-        for host in $(nix flake show . --json | jq ".nixosConfigurations|keys[]" -r); do
-          echo "::group::Diff-closures for ${host}"
-          drv="nixosConfigurations.$host.config.system.build.toplevel"
-          diff_cmd="nix store diff-closures git+file:.?ref=${target_ref}#${drv} .#${drv}"
-          # Get the nice and colorfull output for the logs, running twice won't (significantly) prolong the runtime
-          $diff_cmd
-          echo -e "<details>\n<summary>Diff for ${host}</summary>\n"  >> $GITHUB_STEP_SUMMARY
-          echo '```' >> $GITHUB_STEP_SUMMARY
-          # Strip color codes so that the summary stays readable
-          $diff_cmd | sed -e 's/\x1b\[[0-9;]*m//g' >> $GITHUB_STEP_SUMMARY
-          echo '```' >> $GITHUB_STEP_SUMMARY
-          echo -e "\n</details>" >> $GITHUB_STEP_SUMMARY
-          echo "::endgroup::"
-        done