ci/request-reviews: split off a more reusable reviewer processing script

We can reuse the new process-reviewers.json part for requesting
reviews from maintainers.

ci/request-reviews/default.nix

@@ -15,6 +15,7 @@ stdenvNoCC.mkDerivation {
     root = ./.;
     fileset = lib.fileset.unions [
       ./get-reviewers.sh
+      ./process-reviewers.sh
       ./request-reviews.sh
       ./verify-base-branch.sh
       ./dev-branches.txt

ci/request-reviews/get-reviewers.sh

@@ -1,8 +1,6 @@
 #!/usr/bin/env bash
 
-# Get the code owners of the files changed by a PR,
-# suitable to be consumed by the API endpoint to request reviews:
-# https://docs.github.com/en/rest/pulls/review-requests?apiVersion=2022-11-28#request-reviewers-for-a-pull-request
+# Get the code owners of the files changed by a PR, returning one username per line
 
 set -euo pipefail
 
@@ -10,18 +8,15 @@ log() {
     echo "$@" >&2
 }
 
-if (( "$#" < 7 )); then
-    log "Usage: $0 GIT_REPO OWNERS_FILE BASE_REPO BASE_REF HEAD_REF PR_NUMBER PR_AUTHOR"
+if (( "$#" < 4 )); then
+    log "Usage: $0 GIT_REPO OWNERS_FILE BASE_REF HEAD_REF"
     exit 1
 fi
 
 gitRepo=$1
 ownersFile=$2
-baseRepo=$3
-baseRef=$4
-headRef=$5
-prNumber=$6
-prAuthor=$7
+baseRef=$3
+headRef=$4
 
 tmp=$(mktemp -d)
 trap 'rm -rf "$tmp"' exit
@@ -98,29 +93,4 @@ for file in "${touchedFiles[@]}"; do
 
 done
 
-# Cannot request a review from the author
-if [[ -v users[${prAuthor,,}] ]]; then
-    log "One or more files are owned by the PR author, ignoring"
-    unset 'users[${prAuthor,,}]'
-fi
-
-gh api \
-    -H "Accept: application/vnd.github+json" \
-    -H "X-GitHub-Api-Version: 2022-11-28" \
-    "/repos/$baseRepo/pulls/$prNumber/reviews" \
-    --jq '.[].user.login' > "$tmp/already-reviewed-by"
-
-# And we don't want to rerequest reviews from people who already reviewed
-while read -r user; do
-    if [[ -v users[${user,,}] ]]; then
-        log "User $user is a code owner but has already left a review, ignoring"
-        unset 'users[${user,,}]'
-    fi
-done < "$tmp/already-reviewed-by"
-
-# Turn it into a JSON for the GitHub API call to request PR reviewers
-jq -n \
-    --arg users "${!users[*]}" \
-    '{
-      reviewers: $users | split(" "),
-    }'
+printf "%s\n" "${!users[@]}"

ci/request-reviews/process-reviewers.sh

@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+
+# Process reviewers for a PR, reading line-separated usernames on stdin,
+# returning a JSON suitable to be consumed by the API endpoint to request reviews:
+# https://docs.github.com/en/rest/pulls/review-requests?apiVersion=2022-11-28#request-reviewers-for-a-pull-request
+
+set -euo pipefail
+
+log() {
+    echo "$@" >&2
+}
+
+if (( "$#" < 3 )); then
+    log "Usage: $0 BASE_REPO PR_NUMBER PR_AUTHOR"
+    exit 1
+fi
+
+baseRepo=$1
+prNumber=$2
+prAuthor=$3
+
+tmp=$(mktemp -d)
+trap 'rm -rf "$tmp"' exit
+
+declare -A users=()
+while read -r handle && [[ -n "$handle" ]]; do
+    users[$handle]=
+done
+
+# Cannot request a review from the author
+if [[ -v users[${prAuthor,,}] ]]; then
+    log "One or more files are owned by the PR author, ignoring"
+    unset 'users[${prAuthor,,}]'
+fi
+
+gh api \
+    -H "Accept: application/vnd.github+json" \
+    -H "X-GitHub-Api-Version: 2022-11-28" \
+    "/repos/$baseRepo/pulls/$prNumber/reviews" \
+    --jq '.[].user.login' > "$tmp/already-reviewed-by"
+
+# And we don't want to rerequest reviews from people who already reviewed
+while read -r user; do
+    if [[ -v users[${user,,}] ]]; then
+        log "User $user is a code owner but has already left a review, ignoring"
+        unset 'users[${user,,}]'
+    fi
+done < "$tmp/already-reviewed-by"
+
+# Turn it into a JSON for the GitHub API call to request PR reviewers
+jq -n \
+    --arg users "${!users[*]}" \
+    '{
+      reviewers: $users | split(" "),
+    }'

ci/request-reviews/request-reviews.sh

@@ -78,7 +78,8 @@ if ! "$SCRIPT_DIR"/verify-base-branch.sh "$tmp/nixpkgs.git" "$headRef" "$baseRep
 fi
 
 log "Getting code owners to request reviews from"
-"$SCRIPT_DIR"/get-reviewers.sh "$tmp/nixpkgs.git" "$ownersFile" "$baseRepo" "$baseBranch" "$headRef" "$prNumber" "$prAuthor" > "$tmp/reviewers.json"
+"$SCRIPT_DIR"/get-reviewers.sh "$tmp/nixpkgs.git" "$ownersFile" "$baseBranch" "$headRef" | \
+    "$SCRIPT_DIR"/process-reviewers.sh "$baseRepo" "$prNumber" "$prAuthor" > "$tmp/reviewers.json"
 
 log "Requesting reviews from: $(<"$tmp/reviewers.json")"