Allow custom amp validation

packages/next/export/index.ts

@@ -215,6 +215,9 @@ export default async function(
     hotReloader: null,
     canonicalBase: (nextConfig.amp && nextConfig.amp.canonicalBase) || '',
     isModern: nextConfig.experimental.modern,
+    ampValidator:
+      (nextConfig.experimental.amp && nextConfig.experimental.amp.validator) ||
+      undefined,
   }
 
   const { serverRuntimeConfig, publicRuntimeConfig } = nextConfig

packages/next/export/worker.js

@@ -163,8 +163,8 @@ export default async function({
       }
     }
 
-    const validateAmp = async (html, page) => {
-      const validator = await AmpHtmlValidator.getInstance()
+    const validateAmp = async (html, page, validatorPath) => {
+      const validator = await AmpHtmlValidator.getInstance(validatorPath)
       const result = validator.validateString(html)
       const errors = result.errors.filter(e => e.severity === 'ERROR')
       const warnings = result.errors.filter(e => e.severity !== 'ERROR')
@@ -181,7 +181,7 @@ export default async function({
     }
 
     if (curRenderOpts.inAmpMode) {
-      await validateAmp(html, path)
+      await validateAmp(html, path, curRenderOpts.ampValidator)
     } else if (curRenderOpts.hybridAmp) {
       // we need to render the AMP version
       let ampHtmlFilename = `${ampPath}${sep}index.html`

packages/next/server/next-dev-server.ts

@@ -54,7 +54,11 @@ export default class DevServer extends Server {
       html: string,
       pathname: string
     ) => {
-      return AmpHtmlValidator.getInstance().then(validator => {
+      const validatorPath =
+        this.nextConfig.experimental &&
+        this.nextConfig.experimental.amp &&
+        this.nextConfig.experimental.amp.validator
+      return AmpHtmlValidator.getInstance(validatorPath).then(validator => {
         const result = validator.validateString(html)
         ampValidation(
           pathname,