nix-flake-outputs-size/comment_on_pr.sh

#!/bin/sh

set -eu

util_path="${GITHUB_ACTION_PATH:-.}/utils.sh"

# shellcheck source=utils.sh
. "${util_path}"

# USAGE: json_to_md_rows <FIELD> [JSON_FILE]
#
# JSON_FILE can be piped from stdin
json_to_md_rows() {
	jq --raw-output \
		".$1[]"' | "| `\(.name)` | \(.size) | \(.narSize) |"' "$2" |
		numfmt --suffix=B --to=iec-i --field=4,6
}

# USAGE: json_to_md_rows <FIELD> [JSON_FILE]
#
# JSON_FILE can be piped from stdin
json_to_md_rows_and_change() {
	jq --raw-output \
		".$1[]"' | "| `\(.name)` | \(.size) | \(.sizeChange) | \(.narSize) | \(.narSizeChange) |"' |
		numfmt --suffix=B --to=iec-i --field=4,6,8,10
}

# USAGE: has_elements <FIELD> <JSON_FILE>
has_elements() {
	if [ "${2+set}" = 'set' ]; then
		[ "$(jq ".$1 != []" "$2")" = 'true' ]
	else
		[ "$(jq ".$1 != []")" = 'true' ]
	fi
}

# USAGE: markdown_from_report <REPORT> [BASE_REPORT]
#
# If BASE_REPORT is provided, a comparison will be made
markdown_from_report() {
	cat <<-"EOF"
		# Flake output sizes

		**Definitions:**

		- `Name`: the name of the package/configuration.
		- `Size`: the closure size (size on disk/NAR size + all transitive dependencies).
		- `NAR Size`: the size of the build output (package without the dependencies).
	EOF
	if [ "${2+set}" = "set" ]; then
		cat <<-"EOF"
			- `[NAR] Size Change`: the amount changed compared to the main branch.
		EOF
	fi
	cat <<-"EOF"

		**Tips on reading this data:**

		- For NixOS configurations you generally care only about the `Size` (closure size/size on disk).
		  - Reduce the `Size` by disabling unneeded services/default packages.
		- For Packages you care about both the `Size` and the `NAR Size`.
		  - Reduce the `NAR Size` by reducing the size of the build outputs, e.g. don't copy unnecessary data to the $out dir, optimize binaries for size, etc.
		  - Reduce the `Size` by reducing the dependencies (e.g. `buildInputs`).
		  - Don't worry too much about size, some dependencies are deduplicated, e.g. `glibc` adds ~40MiB to the `Size`, but is generally shared by ~every binary on the system, so, chances are, you are already including it from somewhere else and statically linking with e.g. `musl` is not gonna improve things.
	EOF

	if [ "${2+set}" = "set" ]; then
		compare=$(jq --slurp --from-file "${GITHUB_ACTION_PATH:-.}/compare.jq" "$1" "$2")
		if echo "$compare" | has_elements 'nixosConfigurations'; then
			cat <<-"EOF"
				# NixOS Configurations

				| Name | Size | Size Change | NAR Size | NAR Size Change |
				|------|-----:|------------:|---------:|----------------:|
			EOF
			echo "$compare" | json_to_md_rows_and_change "nixosConfigurations"
			echo
		fi
		if echo "$compare" | has_elements 'packages'; then
			cat <<-"EOF"
				# Packages

				| Name | Size | Size Change | NAR Size | NAR Size Change |
				|------|-----:|------------:|---------:|----------------:|
			EOF
			echo "$compare" | json_to_md_rows_and_change "packages"
			echo
		fi
	else
		if has_elements 'nixosConfigurations' "$1"; then
			cat <<-"EOF"
				# NixOS Configurations

				| Name | Size | NAR Size |
				|------|-----:|---------:|
			EOF
			json_to_md_rows "nixosConfigurations" "$1"
			echo
		fi
		if has_elements 'packages' "$1"; then
			cat <<-"EOF"
				# Packages

				| Name | Size | NAR Size |
				|------|-----:|---------:|
			EOF
			json_to_md_rows "packages" "$1"
			echo
		fi
	fi
}

# Test outside CI
if [ "${CI:-false}" != 'true' ]; then
	markdown_from_report "$@"
	exit 0
fi

log 'Determine head_ref'
# For push & tag events it'll bet GITHUB_REF_NAME, for pull_request events it'll be GITHUB_HEAD_REF
head_ref=${GITHUB_REF_NAME:-$GITHUB_HEAD_REF}

log "Get PR number for $head_ref"
prs=$(curl -X 'GET' \
	"$GITHUB_API_URL/repos/$GITHUB_REPOSITORY/pulls?state=open&sort=recentupdate" \
	-H "Authorization: token $GITHUB_TOKEN" \
	-H 'accept: application/json')

pr_number=$(echo "$prs" |
	jq --arg head_ref "$head_ref" '.[] | select(.head.ref == $head_ref) | .number')

# Protect against running before a PR is made or if it is triggered on the main branch
if [ -z "$pr_number" ]; then
	warn "No PR created for this commit"
	exit 0
fi

log "Retrieved index: $pr_number"
log "Expected PR URL: $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/pulls/$pr_number"

log 'Generating comment body'
comment=$(markdown_from_report "$@")

group 'Comment Data'
log "$comment"
endgroup

data=$(echo '{}' | jq --arg comment "$comment" '.body=$comment')
group 'Request data'
log "$data"
endgroup

curl -o - -X 'POST' \
	"$GITHUB_API_URL/repos/$GITHUB_REPOSITORY/issues/$pr_number/comments" \
	-H 'accept: application/json' \
	-H "Authorization: token $GITHUB_TOKEN" \
	-H 'Content-Type: application/json' \
	-d "$data"