AMP Linter

Overview

A linter for AMP documents: reports errors and suspicious constructions such as images missing or incorrectly sized, missing CORS headers, or invalid metadata.

Usage

Command-line (local build):

# from the amp-toolbox root
$ npm install
$ npm run build # generates packages/linter/dist/cli.js
$ cd packages/linter
$ node dist/cli.js https://amp.dev/

Command-line (from npm):

$ npx @ampproject/toolbox-cli lint https://amp.dev/

Node:

const fs = require("fs");
const linter = require("@ampproject/toolbox-linter");
const cheerio = require("cheerio");

const body = fs.readFileSync("amp-dev.html");
const context = {
  $: cheerio.load(body),
  headers: {},
  url: "https://amp.dev/"
};

linter.MetaCharsetIsFirst(context).then(console.log);

dump-signedexchange

One test has a dependency on the dump-signedexchange go binary. If this is available (installation instructions) at additional check of the application/signed-exchange response will be performed.

Development

Commands/Scripts

These scripts can be invoked in the usual way by npm run XXX if npm install is run in this directory. They can also be invoked from the amp-toolbox root directory without installing locally by lerna run --scope '*/toolbox-linter' XXX. (lerna sets the PATH so that the required binaries are available.)

build

Populates the dist directory with the appropriate *.js and *.d.ts files. Note that tests are not included. This script is intended to be used when building the npm package.

lint

Checks the code for lint errors using prettier.

Running tests

The unit tests run in the context of toolbox project.

# Run all linter tests
npm run test:node -- packages/linter

# Run linter network tests
npm run test:node -- packages/linter/tests/network.test.ts

Suggested Development Workflow

1. Create stub rule in rules/, that always "fails". e.g. it always returns qqqqqq. It should extend the Rule class.
2. Write tests in tests/network.test.ts (If HTTP requests are required). If not then create a directory in tests/local/MyNewTest-1 that contains a source.html (AMP HTML source) and add your test in tests/local.test.ts.
3. Run the test using npm run test:node -- packages/linter in the toolbox root. If the fixtures can't be found, they will be generated automatically (via real network requests). Hopefully your test will fail.
4. Fix the implementation, and re-run the test.