Deprecating cdn.ampproject.org/v0/validator.js in favor of WebAssembly version

Summary

The AMPHTML Validator ensures that critical features of the AMPHTML spec are followed within AMP related documents. It is maintained by a set of rules and engines written in C++ and JavaScript that apply those rules during validation. There are many developer tools that utilize these validator engines to assist in the development of valid AMP documents.

Due to ongoing complexity and developer maintenance of two validator engines, the Caching Working Group is deprecating the native JavaScript validator in favor of a WebAssembly validator which uses the C++ engine.

Existing developer tools such as the Validator Web UI, Chrome Extension, VS Code Extension and Node.js Package have already migrated to the WebAssembly validator.

To inform existing developers using validator.js directly and not through one of these developer tools, the APIs in validator.js will be deprecated to return an error message to update tooling to use validator_wasm.js and it will no longer provide validation. This was released for a short time on Monday, September 13, 2021 before being rollbacked. It will be released again on Thursday, September 23, 2021 pending approval here.

Developers unable to migrate to the WebAssembly validator immediately due to compatibility issues, will be able to utilize a temporary fallback to the native JavaScript validator (validator.20211101.deprecated.js). This will be removed on November 1, 2021.

Motivation

The AMPHTML Validator has two implementations. One in C++ and one in JavaScript. These utilize different HTML parsers which at times can cause differences between validation results of documents. Over time these differences have been reduced. However, there is ongoing complexity and maintenance costs in keeping these two implementations in sync. With a WebAssembly validator version released, it is no longer necessary to continue to endure those costs by deprecating the native JavaScript version in favor of the WebAssembly version.

Impact on Existing Users

Developers utilizing validator.js directly from the Google AMP Cache will need to upgrade to using the WebAssembly version (validator_wasm.js). A temporary fallback version is provided until November 1, 2021.

Alternative Implementation

A temporary fallback version is provided until November 1, 2021 via https://cdn.ampproject.org/v0/validator.20211101.deprecated.js. Ideally they would upgrade to https://cdn.ampproject.org/v0/validator_wasm.js or utilize an existing developer tool such as the Node.js Package.

Additional Context

Example of messaging returned by the deprecated native JavaScript validator via Node.js Package:

$ amphtml-validator --validator.js minimum_valid_amp.html

minimum_valid_amp.html:1:0 The native JavaScript AMPHTML Validator (validator.js) has been turned down. If you are seeing this error, update your tooling to instead load the API compatible WebAssembly AMPHTML Validator (validator_wasm.js) instead.

Example of messaging returned by the deprecated native JavaScript validator via DevTools:

> amp.validator.validateString('test');

validator.js:7 ERROR: The native JavaScript AMPHTML Validator (validator.js) has been turned down. If you are seeing this error, update your tooling to instead load the API compatible WebAssembly AMPHTML Validator (validator_wasm.js) instead.

Notifications

/cc @ampproject/wg-approvers

[kristoferbaxter]

Oh, that makes sense, thanks for the clarification.

@rsimha Not sure if this is on your radar, but wanted to make sure it was known.

[antiphoton]

The WebAssembly validator is not 100% backward compatible with the previous native JavaScript validator, the validator_wasm.js adds an async init function, which must be called before all other functions. The developers need to not only change the URL to validator_wasm.js, but also need to add the statement await amp.validator.init();.

The amp.validator.init is async function because the initialization of WebAssembly is async. However, the public APIs (for example amp.validator.validateString) of the previous native JavaScript validator are declared sync functions, hence it is not possible to make the initialization of WebAssembly to be inside of amp.validator.validateString, and we have to introduce the new amp.validator.init.