Friggin Node.js 10

.github/workflows/check.yml

@@ -45,7 +45,7 @@ jobs:
           NO_ELM_TOOLING_INSTALL: 1
 
       - name: elm-tooling install
-        run: npx --no-install elm-tooling install
+        run: npm run prepare
 
       - name: Flow
         run: npx --no-install flow check

.github/workflows/test.yml

@@ -45,7 +45,7 @@ jobs:
           NO_ELM_TOOLING_INSTALL: 1
 
       - name: elm-tooling install
-        run: npx --no-install elm-tooling install
+        run: npm run prepare
 
       - name: Mocha
         run: npx --no-install mocha tests

elm-tooling-polyfill.js

@@ -0,0 +1,11 @@
+// Only `elm-tooling/getExecutable` supports Node.js 10, the rest of it is
+// Node.js 12+. Luckily, all that’s needed is to polyfill `.flatMap`.
+// We can get rid of this when Node.js 10 becomes EOL 2021-04-30 and support for
+// Node.js 10 is dropped.
+// Note: This is only used during development and CI of node-test-runner, not
+// for users of the npm package.
+if (Array.prototype.flatMap === undefined) {
+  Array.prototype.flatMap = function flatMap(...args) {
+    return [].concat(...this.map(...args));
+  };
+}

package.json

@@ -16,7 +16,7 @@
     "check": "flow check && npm run lint && npm run format:check && npm run review",
     "format:check": "prettier --check . && elm-format elm --validate",
     "format:write": "prettier --write . && elm-format elm --yes",
-    "prepare": "elm-tooling install"
+    "prepare": "node -r ./elm-tooling-polyfill.js node_modules/elm-tooling/index.js install"
   },
   "repository": {
     "type": "git",