Adds support for tailwind.config.cjs files to CLI

Co-authored-by: Nate Moore <nate@natemoo.re>

integrations/tailwindcss-cli/tests/cli.test.js

@@ -464,4 +464,62 @@ describe('Init command', () => {
       `)
     )
   })
+
+  test('--help in ESM package', async () => {
+    let pkg = await readOutputFile('../package.json')
+
+    await writeInputFile('../package.json', JSON.stringify({
+      ...JSON.parse(pkg),
+      type: 'module',
+    }))
+
+    let { combined } = await $(`${EXECUTABLE} init --help`)
+
+    expect(dedent(combined)).toEqual(
+      dedent(`
+        tailwindcss v${version}
+
+        Usage:
+           tailwindcss init [options]
+
+        Options:
+           -f, --full               Initialize a full \`tailwind.config.cjs\` file
+           -p, --postcss            Initialize a \`postcss.config.cjs\` file
+               --types              Add TypeScript types for the \`tailwind.config.cjs\` file
+           -h, --help               Display usage information
+      `)
+    )
+
+    await writeInputFile('../package.json', pkg)
+  })
+
+  test('cjs config created when in ESM package', async () => {
+    cleanupFile('tailwind.config.cjs')
+
+    let pkg = await readOutputFile('../package.json')
+
+    await writeInputFile('../package.json', JSON.stringify({
+      ...JSON.parse(pkg),
+      type: 'module',
+    }))
+
+    let { combined } = await $(`${EXECUTABLE} init`)
+
+    expect(combined).toMatchInlineSnapshot(`
+      "
+      Created Tailwind CSS config file: tailwind.config.cjs
+      "
+    `)
+
+    expect(await fileExists('./tailwind.config.cjs')).toBe(true)
+
+    // Not a clean way to test this.
+    expect(await readOutputFile('../tailwind.config.cjs')).toContain('module.exports =')
+
+    expect(await readOutputFile('../tailwind.config.cjs')).not.toContain(
+      `/** @type {import('tailwindcss/types').Config} */`
+    )
+
+    await writeInputFile('../package.json', pkg)
+  })
 })

src/cli.js

@@ -23,7 +23,21 @@ let env = {
   DEBUG: process.env.DEBUG !== undefined && process.env.DEBUG !== '0',
 }
 
-let configs = {
+function isESM() {
+  const pkgPath = path.resolve('./package.json')
+
+  try {
+    let pkg = JSON.parse(fs.readFileSync(pkgPath, 'utf8'))
+    return pkg.type && pkg.type === 'module'
+  } catch (err) {
+    return false
+  }
+}
+
+let configs = isESM() ? {
+  tailwind: 'tailwind.config.cjs',
+  postcss: 'postcss.config.cjs',
+} : {
   tailwind: 'tailwind.config.js',
   postcss: 'postcss.config.js',
 }