Move install commands to postinstall script

Closes #117
Closes #163
Closes #161

package.json

@@ -13,6 +13,7 @@
   "author": "Karl Horky <karl.horky@gmail.com>",
   "license": "MIT",
   "scripts": {
+    "postinstall": "scripts/postinstall.js",
     "postpublish": "cd __tests__ && yarn update-config-version"
   },
   "devDependencies": {

readme.md

@@ -9,17 +9,7 @@ UpLeveled ESLint defaults for programming in JavaScript, TypeScript, React and N
 To add ESLint configuration to a project, install the dependencies and add the config files:
 
 ```sh
-CI=true npx install-peerdeps@latest --yarn --dev @upleveled/eslint-config-upleveled
-cp node_modules/@upleveled/eslint-config-upleveled/templates/{*,.eslint*} .
-grep -Fxq ".eslintcache" .gitignore || printf "\n.eslintcache" >> .gitignore
-grep -Fxq ".tsbuildinfo" .gitignore || printf "\n*.tsbuildinfo" >> .gitignore
-node node_modules/@upleveled/eslint-config-upleveled/scripts/install.js
-```
-
-If you have a monorepo using Yarn Workspaces and would like to install the config in the workspace root, change the first line to this:
-
-```sh
-CI=true npx install-peerdeps@latest --yarn --dev @upleveled/eslint-config-upleveled --extra-args "-W"
+yarn add --dev @upleveled/eslint-config-upleveled
 ```
 
 <!--

scripts/postinstall.js

@@ -0,0 +1,155 @@
+#!/usr/bin/env node
+
+import { execSync } from 'node:child_process';
+import {
+  existsSync,
+  readdirSync,
+  readFileSync,
+  rmSync,
+  writeFileSync,
+} from 'node:fs';
+import { dirname, join, resolve } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const { peerDependencies } = JSON.parse(
+  readFileSync(
+    resolve(dirname(fileURLToPath(import.meta.url)), '..', 'package.json'),
+    'utf-8',
+  ),
+);
+
+// Remove SafeQL dependencies for now on Windows
+// https://github.com/ts-safeql/safeql/issues/80
+if (process.platform === 'win32') {
+  delete peerDependencies['@ts-safeql/eslint-plugin'];
+  delete peerDependencies['libpg-query'];
+}
+
+const packageJsonPath = join(process.cwd(), 'package.json');
+const packageJsonObj = JSON.parse(readFileSync(packageJsonPath, 'utf-8'));
+
+// Add all config peerDependencies to devDependencies of
+// project, upgrading existing package versions and
+// sorting alphabetically
+packageJsonObj.devDependencies = Object.fromEntries(
+  Object.entries({
+    ...packageJsonObj.devDependencies,
+    ...peerDependencies,
+  }).sort(),
+);
+
+packageJsonObj.resolutions = {
+  ...packageJsonObj.resolutions,
+  // Force installation of the "dependencies" version of these
+  // ESLint dependencies to avoid conflicting version numbers
+  // between `eslint-config-react-app` and
+  // `@upleveled/eslint-config-upleveled` (they use the same
+  // ESLint dependencies, but may have slightly different
+  // versions).
+  //
+  // These conflicts can result in ESLint errors like:
+  //
+  // ESLint couldn't determine the plugin "import" uniquely.
+  //
+  // - /home/runner/work/preflight/preflight/node_modules/eslint-plugin-import/lib/index.js (loaded in ".eslintrc.cjs » @upleveled/eslint-config-upleveled")
+  // - /home/runner/work/preflight/preflight/node_modules/eslint-config-react-app/node_modules/eslint-plugin-import/lib/index.js (loaded in ".eslintrc.cjs » @upleveled/eslint-config-upleveled » eslint-config-react-app")
+  ...[
+    '@typescript-eslint/eslint-plugin',
+    '@typescript-eslint/parser',
+    'eslint-plugin-import',
+    'eslint-plugin-jest',
+    'eslint-plugin-jsx-a11y',
+    'eslint-plugin-react',
+    'eslint-plugin-react-hooks',
+  ].reduce(
+    (resolutions, packageName) => ({
+      ...resolutions,
+      [packageName]: packageJsonObj.devDependencies[packageName],
+    }),
+    {},
+  ),
+  '@typescript-eslint/utils':
+    packageJsonObj.devDependencies['@typescript-eslint/parser'],
+};
+
+writeFileSync(packageJsonPath, JSON.stringify(packageJsonObj, null, 2) + '\n');
+
+console.log('Installing ESLint config dependencies...');
+
+execSync('yarn install', { stdio: 'inherit' });
+
+console.log('✅ Done installing dependencies');
+
+console.log('Writing config files...');
+
+const templatePath = resolve(
+  dirname(fileURLToPath(import.meta.url)),
+  '..',
+  'templates',
+);
+
+const templateFileNamesAndPaths = /** @type {[string, string][]} */ (
+  readdirSync(templatePath).map((name) => [name, join(templatePath, name)])
+);
+
+for (const [templateFileName, templateFilePath] of templateFileNamesAndPaths) {
+  const destinationFilePath = join(process.cwd(), templateFileName);
+
+  if (existsSync(destinationFilePath)) {
+    console.log(`Skipping update to ${templateFileName} (already exists)`);
+    continue;
+  }
+
+  try {
+    writeFileSync(destinationFilePath, readFileSync(templateFilePath, 'utf-8'));
+    console.log(`Wrote ${templateFileName}`);
+  } catch (err) {
+    console.error('err', err);
+  }
+}
+
+console.log('✅ Done updating config files');
+
+console.log('Updating .gitignore...');
+
+const gitignorePath = join(process.cwd(), '.gitignore');
+
+/** @type {string[]} */
+let gitignoreContentLines = [];
+
+try {
+  gitignoreContentLines = readFileSync(gitignorePath, 'utf-8').split('\n');
+} catch (err) {
+  // Swallow error in case .gitignore doesn't exist yet
+}
+
+for (const ignorePath of ['.eslintcache', '*.tsbuildinfo']) {
+  if (gitignoreContentLines.includes(ignorePath)) {
+    continue;
+  }
+
+  gitignoreContentLines.push(ignorePath);
+}
+
+writeFileSync(
+  gitignorePath,
+  gitignoreContentLines.join('\n') +
+    // Add trailing newline if last line is not empty
+    (gitignoreContentLines.at(-1) === '' ? '' : '\n'),
+);
+
+console.log('✅ Done updating .gitignore');
+
+try {
+  if (
+    readFileSync(join(process.cwd(), '.eslintrc.json'), 'utf-8').trim() ===
+    `{
+  "extends": "next/core-web-vitals"
+}`
+  ) {
+    rmSync(join(process.cwd(), '.eslintrc.json'));
+    console.log('Removed default Next.js ESLint config');
+  }
+} catch (err) {
+  // Swallow error if .eslintrc.json file does not exist
+}