Adds a setup TypeScript script, and docs in the README (#140)

* Adds a setup TypeScript script, and docs in the README

* Adds a CTA to the TS script

* Update scripts/setupTypeScript.js

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>

* Fix README

* emphasise that the script should be run immediately

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
Co-authored-by: Rich Harris <richard.a.harris@gmail.com>

README.md

@@ -57,6 +57,19 @@ If you're building a single-page app (SPA) with multiple routes, sirv needs to b
 "start": "sirv public --single"
 ```
 
+## Using TypeScript
+
+This template comes with a script to set up a TypeScript development environment, you can run it immediately after cloning the template with:
+
+```bash
+node scripts/setupTypeScript.js
+```
+
+Or remove the script via:
+
+```bash
+rm scripts/setupTypeScript.js
+```
 
 ## Deploying to the web
 

scripts/setupTypeScript.js

@@ -0,0 +1,115 @@
+// @ts-check
+
+/** This script modifies the project to support TS code in .svelte files like:
+
+  <script lang="ts">
+  	export let name: string;
+  </script>
+ 
+  As well as validating the code for CI.
+  */
+
+/**  To work on this script:
+  rm -rf test-template template && git clone sveltejs/template test-template && node scripts/setupTypeScript.js test-template
+*/
+
+const fs = require("fs")
+const path = require("path")
+const { argv } = require("process")
+
+const projectRoot = argv[2] || path.join(__dirname, "..")
+
+// Add deps to pkg.json
+const packageJSON = JSON.parse(fs.readFileSync(path.join(projectRoot, "package.json"), "utf8"))
+packageJSON.devDependencies = Object.assign(packageJSON.devDependencies, {
+  "svelte-check": "^0.1.0",
+  "svelte-preprocess": "^4.0.0",
+  "@rollup/plugin-typescript": "^4.0.0",
+  "typescript": "^3.9.3",
+  "tslib": "^2.0.0",
+  "@tsconfig/svelte": "^1.0.0"
+})
+
+// Add script for checking
+packageJSON.scripts = Object.assign(packageJSON.scripts, {
+  "validate": "svelte-check"
+})
+
+// Write the package JSON
+fs.writeFileSync(path.join(projectRoot, "package.json"), JSON.stringify(packageJSON, null, "  "))
+
+// mv src/main.js to main.ts - note, we need to edit rollup.config.js for this too
+const beforeMainJSPath = path.join(projectRoot, "src", "main.js")
+const afterMainTSPath = path.join(projectRoot, "src", "main.ts")
+fs.renameSync(beforeMainJSPath, afterMainTSPath)
+
+// Switch the app.svelte file to use TS
+const appSveltePath = path.join(projectRoot, "src", "App.svelte")
+let appFile = fs.readFileSync(appSveltePath, "utf8")
+appFile = appFile.replace("<script>", '<script lang="ts">')
+appFile = appFile.replace("export let name;", 'export let name: string;')
+fs.writeFileSync(appSveltePath, appFile)
+
+// Edit rollup config
+const rollupConfigPath = path.join(projectRoot, "rollup.config.js")
+let rollupConfig = fs.readFileSync(rollupConfigPath, "utf8")
+
+// Edit imports
+rollupConfig = rollupConfig.replace(`'rollup-plugin-terser';`, `'rollup-plugin-terser';
+import sveltePreprocess from 'svelte-preprocess';
+import typescript from '@rollup/plugin-typescript';`)
+
+// Replace name of entry point
+rollupConfig = rollupConfig.replace(`'src/main.js'`, `'src/main.ts'`)
+
+// Add preprocess to the svelte config, this is tricky because there's no easy signifier.
+// Instead we look for `css:` then the next `}` and add the preprocessor to that
+let foundCSS = false
+let match
+
+// https://regex101.com/r/OtNjwo/1
+const configEditor = new RegExp(/css:.|\n*}/gmi)
+while (( match = configEditor.exec(rollupConfig)) != null) {
+  if (foundCSS) {
+    const endOfCSSIndex = match.index + 1
+    rollupConfig = rollupConfig.slice(0, endOfCSSIndex) + ",\n			preprocess: sveltePreprocess()," + rollupConfig.slice(endOfCSSIndex);
+    break
+  }
+  if (match[0].includes("css:")) foundCSS = true
+}
+
+
+// Add TypeScript
+rollupConfig = rollupConfig.replace("commonjs(),", 'commonjs(),\n\t\ttypescript({ sourceMap: !production }),')
+fs.writeFileSync(rollupConfigPath, rollupConfig)
+
+// Add TSConfig
+const tsconfig = `{
+  "extends": "@tsconfig/svelte/tsconfig.json",
+
+  "include": ["src/**/*"],
+  "exclude": ["node_modules/*", "__sapper__/*", "public/*"],
+}`
+const tsconfigPath =  path.join(projectRoot, "tsconfig.json")
+fs.writeFileSync(tsconfigPath, tsconfig)
+
+// Delete this script, but not during testing
+if (!argv[2]) {
+  // Remove the script
+  fs.unlinkSync(path.join(__filename))
+  // Remove the scripts folder
+  fs.rmdirSync(path.join(__dirname))
+}
+
+// Adds the extension recommendation
+fs.mkdirSync(path.join(projectRoot, ".vscode"))
+fs.writeFileSync(path.join(projectRoot, ".vscode", "extensions.json"), `{
+  "recommendations": ["svelte.svelte-vscode"]
+}
+`)
+
+console.log("Converted to TypeScript.")
+
+if (fs.existsSync(path.join(projectRoot, "node_modules"))) {
+  console.log("\nYou will need to re-run your dependency manager to get started.")
+}