feat: add opt-in usage of create as underlying files engine (#1670)

## PR Checklist

- [x] Addresses an existing open issue: fixes #1181
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Adds an intentionally undocumented option for a `CTA_CREATE_ENGINE`
environment variable. It switches the file creation engine from the
current (now, legacy!) system to the [`create`
engine](https://github.com/JoshuaKGoldberg/create):

```shell
CTA_CREATE_ENGINE=true node ./bin/index.js ...
```

Next up after this will be to wholly remove the current/legacy files,
then move onto commands and network requests, then options parsing
altogether. Those will be followup PRs.

💝

README.md

@@ -1,6 +1,6 @@
 <h1 align="center">Create TypeScript App</h1>
 
-<p align="center">Quickstart-friendly TypeScript template with comprehensive, configurable, opinionated tooling. 💝</p>
+<p align="center">Quickstart-friendly TypeScript template with comprehensive, configurable, opinionated tooling. ❤️‍🔥</p>
 
 <p align="center">
 	<!-- prettier-ignore-start -->

cspell.json

@@ -12,17 +12,20 @@
 	],
 	"words": [
 		"allcontributors",
+		"Anson",
 		"apexskier",
 		"arethetypeswrong",
 		"automerge",
 		"codespace",
+		"dbaeumer",
 		"execa",
 		"infile",
 		"joshuakgoldberg",
 		"markdownlintignore",
 		"mtfoley",
 		"outro",
 		"tada",
-		"tseslint"
+		"tseslint",
+		"wontfix"
 	]
 }

eslint.config.js

@@ -97,9 +97,7 @@ export default tseslint.config(
 	{
 		extends: [vitest.configs.recommended],
 		files: ["**/*.test.*"],
-		rules: {
-			"@typescript-eslint/no-unsafe-assignment": "off",
-		},
+		rules: { "@typescript-eslint/no-unsafe-assignment": "off" },
 	},
 	{
 		extends: [yml.configs["flat/recommended"], yml.configs["flat/prettier"]],

knip.json

@@ -1,6 +1,6 @@
 {
 	"$schema": "https://unpkg.com/knip@latest/schema.json",
-	"entry": ["src/index.ts!", "script/*e2e.js"],
+	"entry": ["script/*e2e.js", "src/index.ts!", "src/**/*.test.*"],
 	"ignoreExportsUsedInFile": { "interface": true, "type": true },
 	"project": ["src/**/*.ts!", "script/**/*.js"]
 }

package.json

@@ -1,7 +1,7 @@
 {
 	"name": "create-typescript-app",
 	"version": "1.75.0",
-	"description": "Quickstart-friendly TypeScript template with comprehensive, configurable, opinionated tooling. 💝",
+	"description": "Quickstart-friendly TypeScript template with comprehensive, configurable, opinionated tooling. ❤️‍🔥",
 	"repository": {
 		"type": "git",
 		"url": "https://github.com/JoshuaKGoldberg/create-typescript-app"
@@ -45,6 +45,7 @@
 		"@prettier/sync": "^0.5.2",
 		"all-contributors-for-repository": "^0.3.0",
 		"chalk": "^5.3.0",
+		"create": "0.1.0-alpha.0",
 		"execa": "^9.5.1",
 		"get-github-auth-token": "^0.1.0",
 		"git-remote-origin-url": "^4.0.0",
@@ -54,6 +55,7 @@
 		"npm-user": "^6.1.1",
 		"octokit": "^4.0.2",
 		"parse-author": "^2.0.0",
+		"parse-package-name": "^1.0.0",
 		"prettier": "^3.4.1",
 		"replace-in-file": "^8.2.0",
 		"rimraf": "^6.0.1",
@@ -76,6 +78,7 @@
 		"@vitest/eslint-plugin": "1.1.14",
 		"c8": "10.1.2",
 		"console-fail-test": "0.5.0",
+		"create-testers": "0.1.0-alpha.0",
 		"cspell": "8.16.1",
 		"eslint": "9.16.0",
 		"eslint-plugin-jsdoc": "50.6.0",

script/__snapshots__/migrate-test-e2e.ts.snap

@@ -114,42 +114,6 @@ exports[`expected file changes > README.md 1`] = `
 +> 💙 This package was templated with [\`create-typescript-app\`](https://github.com/JoshuaKGoldberg/create-typescript-app)."
 `;
 
-exports[`expected file changes > cspell.json 1`] = `
-"--- a/cspell.json
-+++ b/cspell.json
-@@ ... @@
- 		".all-contributorsrc",
- 		".github",
- 		"CHANGELOG.md",
--		"coverage*",
-+		"coverage",
- 		"lib",
- 		"node_modules",
--		"pnpm-lock.yaml",
--		"script/__snapshots__"
-+		"pnpm-lock.yaml"
- 	],
- 	"words": [
- 		"allcontributors",
-@@ ... @@
- 		"arethetypeswrong",
- 		"automerge",
- 		"codespace",
--		"execa",
-+		"contributorsrc",
- 		"infile",
- 		"joshuakgoldberg",
- 		"markdownlintignore",
- 		"mtfoley",
- 		"outro",
- 		"tada",
--		"tseslint"
-+		"tseslint",
-+		"wontfix"
- 	]
- }"
-`;
-
 exports[`expected file changes > eslint.config.js 1`] = `
 "--- a/eslint.config.js
 +++ b/eslint.config.js
@@ -238,14 +202,27 @@ exports[`expected file changes > knip.json 1`] = `
 @@ ... @@
  {
  	"$schema": "https://unpkg.com/knip@latest/schema.json",
--	"entry": ["src/index.ts!", "script/*e2e.js"],
+-	"entry": ["script/*e2e.js", "src/index.ts!", "src/**/*.test.*"],
 +	"entry": ["src/index.ts!"],
  	"ignoreExportsUsedInFile": { "interface": true, "type": true },
 -	"project": ["src/**/*.ts!", "script/**/*.js"]
 +	"project": ["src/**/*.ts!"]
  }"
 `;
 
+exports[`expected file changes > package.json 1`] = `
+"--- a/package.json
++++ b/package.json
+@@ ... @@
+ 		"lint-staged": "15.2.10",
+ 		"markdownlint": "0.36.1",
+ 		"markdownlint-cli": "0.43.0",
++		"prettier": "^3.4.1",
+ 		"prettier-plugin-curly": "0.3.1",
+ 		"prettier-plugin-packagejson": "2.5.6",
+ 		"prettier-plugin-sh": "0.14.0","
+`;
+
 exports[`expected file changes > tsconfig.json 1`] = `
 "--- a/tsconfig.json
 +++ b/tsconfig.json

script/migrate-test-e2e.ts

@@ -11,12 +11,15 @@ const filesExpectedToBeChanged = [
 	".github/workflows/ci.yml",
 	".gitignore",
 	".prettierignore",
-	"cspell.json",
 	"eslint.config.js",
+	"package.json",
 	"tsconfig.json",
 ];
 
 const filesThatMightBeChanged = new Set([
+	// For now, ignore typos cspell is picking up from migration snapshots.
+	"cspell.json",
+
 	"script/__snapshots__/migrate-test-e2e.ts.snap",
 	...filesExpectedToBeChanged,
 ]);

src/create/createWithOptions.ts

@@ -1,8 +1,13 @@
 import { $ } from "execa";
 
-import { withSpinner, withSpinners } from "../shared/cli/spinners.js";
+import {
+	LabeledSpinnerTask,
+	withSpinner,
+	withSpinners,
+} from "../shared/cli/spinners.js";
 import { createCleanupCommands } from "../shared/createCleanupCommands.js";
 import { doesRepositoryExist } from "../shared/doesRepositoryExist.js";
+import { isUsingCreateEngine } from "../shared/isUsingCreateEngine.js";
 import { GitHubAndOptions } from "../shared/options/readOptions.js";
 import { addToolAllContributors } from "../steps/addToolAllContributors.js";
 import { clearLocalGitTags } from "../steps/clearLocalGitTags.js";
@@ -20,12 +25,16 @@ export async function createWithOptions({ github, options }: GitHubAndOptions) {
 				await writeStructure(options);
 			},
 		],
-		[
-			"Writing README.md",
-			async () => {
-				await writeReadme(options);
-			},
-		],
+		...(isUsingCreateEngine()
+			? []
+			: [
+					[
+						"Writing README.md",
+						async () => {
+							await writeReadme(options);
+						},
+					] satisfies LabeledSpinnerTask<void>,
+				]),
 	]);
 
 	if (!options.excludeAllContributors && !options.skipAllContributorsApi) {

src/index.ts

@@ -1,2 +1,8 @@
 export * from "./greet.js";
+
+// If you're using create-typescript-app as a template, ignore these.
+// They're plumbing for the create engine. :)
+export * from "./next/blocks/index.js";
+export { default } from "./next/template.js";
+
 export * from "./types.js";