ci: add job to check contract sizes

.github/workflows/contracts_size.yml

@@ -0,0 +1,25 @@
+name: Contract sizes
+
+on:
+  pull_request:
+    branches:
+      - main
+  push:
+    branches:
+      - main
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          submodules: recursive
+
+      - name: Install Foundry
+        uses: foundry-rs/foundry-toolchain@v1
+
+      - name: Check contract sizes
+        run: forge build --sizes | ./check_contracts_size.sh

check_contracts_size.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Simple script to parse the output of `forge build --sizes` and error out if a contract's size goes beyond
+# the allowed limit.
+# Use it with:
+# 	$ forge build --sizes | ./check_contracts_size.sh
+# 	$ ./check_contracts_size.sh < sizes.txt
+# 	$ ./check_contracts_size.sh sizes.txt
+
+
+# this matches lines like this
+# '| Dispatcher                      | 25.698    | -1.122      |'
+pattern='^[ |]+([^ ]+)[ |]+([-]?[0-9\.]+)[ |]+([-]?[0-9\.]+)[ |]+$'
+
+while read -r line; do
+  if [[ "$line" =~ $pattern ]]; then
+	name="${BASH_REMATCH[1]}"
+	size="${BASH_REMATCH[2]}"
+	margin="${BASH_REMATCH[3]}"
+
+	# use bc because bash doesn't like floating point math
+	if [ "$( bc <<< "$margin < 0" )" = '1' ]; then
+		echo "Contract '$name' ($size kB) is too large to be deployed"
+		exit 1
+	fi
+  fi
+done < "${1:-/dev/stdin}"