Fix "Missing visitor keys for 'undefined'" error with multiple Prettier copies

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 /dist
+plugin-dist

CHANGELOG.md

@@ -7,7 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet!
+### Fixed
+
+- Fix "Missing visitor keys for 'undefined'" error when multiple copies of Prettier exist in a dependency tree ([#469](https://github.com/tailwindlabs/prettier-plugin-tailwindcss/issues/469))
 
 ## [0.8.1] - 2026-07-15
 

src/index.ts

@@ -1065,6 +1065,15 @@ let html = defineTransform<HtmlNode>({
     vue: { dynamicAttrs: [':class', 'v-bind:class'] },
   },
 
+  // Use the printer from the same `prettier/plugins/html` module the parsers
+  // come from. When multiple copies of Prettier exist in a dependency tree the
+  // AST produced by our copy may not match what the running Prettier's builtin
+  // printer expects (e.g. Prettier v3.7 renamed the HTML AST `type` field to
+  // `kind`) causing a "Missing visitor keys for 'undefined'" error.
+  printers: {
+    html: {},
+  },
+
   transform: transformHtml,
 })
 

tests/fixtures.test.ts

@@ -160,4 +160,24 @@ describe('fixtures', () => {
       expect(formatted.trim()).toEqual(expected.trim())
     })
   }
+
+  // https://github.com/tailwindlabs/prettier-plugin-tailwindcss/issues/469
+  test.concurrent('multiple copies of Prettier in a dependency tree', async ({ expect }) => {
+    let fixturePath = path.resolve(__dirname, 'fixtures/prettier-mismatch')
+    let pluginCopyPath = path.resolve(fixturePath, 'plugin-dist')
+
+    // Copy the built plugin into the fixture so it resolves the fixture's
+    // copy of Prettier while the CLI runs the repo's copy
+    await fs.cp(path.resolve(__dirname, '../dist'), pluginCopyPath, { recursive: true })
+
+    let inputPath = path.resolve(fixturePath, 'index.html')
+    let outputPath = path.resolve(fixturePath, 'output.html')
+    let cmd = `${binPath} ${inputPath} --plugin ${pluginCopyPath}/index.mjs`
+
+    let results = await execAsync(cmd)
+    let formatted = results.stdout.replace(/\r\n/g, '\n')
+    let expected = await fs.readFile(outputPath, 'utf-8').then((c) => c.replace(/\r\n/g, '\n'))
+
+    expect(formatted.trim()).toEqual(expected.trim())
+  })
 })

tests/fixtures/prettier-mismatch/index.html

@@ -0,0 +1 @@
+<div class="sm:p-0 p-0"></div>

tests/fixtures/prettier-mismatch/output.html

@@ -0,0 +1 @@
+<div class="p-0 sm:p-0"></div>

tests/fixtures/prettier-mismatch/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "prettier": "3.6.2"
+  }
+}