feat: automatic create tsconfig for editor support on functions

Fixes https://github.com/netlify/pod-dev-foundations/issues/595

src/commands/functions/functions-create.mjs

@@ -16,6 +16,7 @@ import fetch from 'node-fetch'
 import ora from 'ora'
 
 import { fileExistsAsync } from '../../lib/fs.mjs'
+import { checkTsconfigForV2Api } from '../../lib/functions/check-tsconfig-for-v2-api.mjs'
 import { getAddons, getCurrentAddon, getSiteData } from '../../utils/addons/prepare.mjs'
 import { NETLIFYDEVERR, NETLIFYDEVLOG, NETLIFYDEVWARN, chalk, error, log } from '../../utils/command-helpers.mjs'
 import { getDotEnvVariables, injectEnvVariables } from '../../utils/dev.mjs'
@@ -715,6 +716,10 @@ const functionsCreate = async (name, options, command) => {
   const functionsDir =
     functionType === 'edge' ? await ensureEdgeFuncDirExists(command) : await ensureFunctionDirExists(command)
 
+  if (functionType === 'serverless') {
+    await checkTsconfigForV2Api({ functionsDir })
+  }
+
   /* either download from URL or scaffold from template */
   const mainFunc = options.url ? downloadFromURL : scaffoldFromTemplate
   await mainFunc(command, options, name, functionsDir, functionType)

src/lib/functions/check-tsconfig-for-v2-api.mjs

@@ -0,0 +1,62 @@
+// @ts-check
+import { existsSync } from 'fs'
+import { writeFile } from 'fs/promises'
+import { createRequire } from 'module'
+import { join } from 'path'
+
+import { NETLIFYDEVLOG, NETLIFYDEVWARN, chalk, log } from '../../utils/command-helpers.mjs'
+
+/**
+ * The `tsconfig.json` we are going to write to the functions directory.
+ * We use a template string instead of JSON.stringify to be able to add comments to the JSON.
+ * Comments inside the JSON are accepted by TypeScript and tsconfig.
+ */
+const TSCONFIG_TMPL = `{
+  // "extends": "../tsconfig.json", /** If you want to share configuration enable the extends property (like strict: true) */
+  "compilerOptions": {
+    "noEmit": true /** This tsconfig.json is only used for type checking and editor support */,
+    "module": "ESNext",
+    "moduleResolution": "Bundler" /** This is needed to use .ts file extensions as we bundle it */,
+    "allowImportingTsExtensions": true /** This allows using .ts file extension instead of the standard .js extension. We allow this for better compatibility with Deno Edge Functions */,
+    "checkJs": true /** Enable type checking in JavaScript files as well */,
+    "allowJs": true /** Make JavaScript files part of the program as well */
+  }
+}
+`
+
+/**
+ * Function that is responsible for validating the typescript configuration for serverless functions.
+ * It validates the `tsconfig.json` settings and if they don't comply it will throw an error.
+ * @param {object} config
+ * @param {string|undefined} config.functionsDir An absolute path to the functions directory
+ */
+export async function checkTsconfigForV2Api(config) {
+  // if no functionsDir is specified or the dir does not exist just return
+  if (!config.functionsDir || !existsSync(config.functionsDir)) {
+    return
+  }
+
+  try {
+    const require = createRequire(config.functionsDir)
+    require.resolve('@netlify/functions')
+  } catch {
+    log(
+      `${NETLIFYDEVWARN} Please install the ${chalk.dim(
+        '@netlify/functions',
+      )} package to get a better typed experience!`,
+    )
+  }
+  const tsconfig = join(config.functionsDir, 'tsconfig.json')
+
+  if (existsSync(tsconfig)) {
+    return
+  }
+
+  await writeFile(tsconfig, TSCONFIG_TMPL, 'utf-8')
+
+  log(
+    `${NETLIFYDEVLOG} Successfully created a ${chalk.dim(
+      'tsconfig.json',
+    )} file in your functions folder for better Editor support!`,
+  )
+}

src/lib/functions/netlify-function.mjs

@@ -8,6 +8,8 @@ import semver from 'semver'
 import { error as errorExit } from '../../utils/command-helpers.mjs'
 import { BACKGROUND } from '../../utils/functions/get-functions.mjs'
 
+import { checkTsconfigForV2Api } from './check-tsconfig-for-v2-api.mjs'
+
 const TYPESCRIPT_EXTENSIONS = new Set(['.cts', '.mts', '.ts'])
 const V2_MIN_NODE_VERSION = '18.0.0'
 
@@ -138,6 +140,13 @@ export default class NetlifyFunction {
 
     try {
       const { includedFiles = [], schedule, srcFiles, ...buildData } = await this.buildQueue
+
+      if (buildData.runtimeAPIVersion === 2) {
+        // Check f the tsconfig.json file exists for the editor support.
+        // If not create it
+        await checkTsconfigForV2Api({ functionsDir: this.directory })
+      }
+
       const srcFilesSet = new Set(srcFiles)
       const srcFilesDiff = this.getSrcFilesDiff(srcFilesSet)