Support node v18 via fetch polyfill

.github/workflows/ci.yaml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [14, 16]
+        node: [14, 16, 18]
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
@@ -32,7 +32,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
-          node-version: 14
+          node-version: 18
       - run: npm install
       - run: npm test
         env:
@@ -43,7 +43,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
-          node-version: 14
+          node-version: 18
       - run: npm install
       - run: npm run lint
   docs:
@@ -52,7 +52,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions/setup-node@v3
         with:
-          node-version: 14
+          node-version: 18
       - run: npm install
       - run: npm run docs
       - uses: JustinBeckwith/linkinator-action@v1

package.json

@@ -5,7 +5,7 @@
   "main": "./build/src/index.js",
   "bin": "./build/src/bin/release-please.js",
   "scripts": {
-    "test": "cross-env ENVIRONMENT=test LC_ALL=en c8 mocha --recursive --timeout=5000 build/test",
+    "test": "cross-env ENVIRONMENT=test LC_ALL=en c8 mocha --node-option no-experimental-fetch --require build/test/_fetch-polyfill.js --recursive --timeout=5000 build/test",
     "docs": "echo add docs tests",
     "test:snap": "SNAPSHOT_UPDATE=1 LC_ALL=en npm test",
     "clean": "gts clean",
@@ -51,6 +51,7 @@
     "@types/lerna__run-topologically": "^5.1.0",
     "@types/mocha": "^9.0.0",
     "@types/node": "^18.0.0",
+    "@types/node-fetch": "^2.6.4",
     "@types/pino": "^7.0.0",
     "@types/semver": "^7.0.0",
     "@types/sinon": "^10.0.0",
@@ -93,6 +94,7 @@
     "https-proxy-agent": "^5.0.1",
     "js-yaml": "^4.0.0",
     "jsonpath": "^1.1.1",
+    "node-fetch": "^2.7.0",
     "node-html-parser": "^6.0.0",
     "parse-github-repo-url": "^1.4.1",
     "semver": "^7.0.0",
@@ -107,4 +109,4 @@
   "engines": {
     "node": ">=14.0.0"
   }
-}
+}

test/_fetch-polyfill.ts

@@ -0,0 +1,16 @@
+// nock, used to mock HTTP requests, currently does not support the undici network stack from node v18+. As a
+// consequence node native fetch isn't supported either and won't be intercepted.
+// See https://github.com/nock/nock/issues/2183 and https://github.com/nock/nock/issues/2397.
+//
+// This file replace the native fetch by the polyfill node-fetch when node v18 is run with the flag
+// --no-experimental-fetch. That's only intended as a temporary solution, the experimental flag is expected to be
+// removed starting from node v22.
+import fetch, {Headers, Request, Response} from 'node-fetch';
+
+/* eslint-disable @typescript-eslint/no-explicit-any */
+if (!globalThis.fetch) {
+  (globalThis as any).fetch = fetch;
+  (globalThis as any).Headers = Headers;
+  (globalThis as any).Request = Request;
+  (globalThis as any).Response = Response;
+}