webpack-ruleset

WebpackRuleset

WebpackRuleset is a slimmed down version of webpack/lib/RuleSet for matching, modifying, and inserting rules in webpack config. Webpack's included RuleSet class normalizes it's rule set, which means the list of loaders returned is not the original rules from config. This class simulates what Webpack's RuleSet does, but keeps a reference to the original rules from config. This allows WebpackRuleset to be used to mutate a Webpack config in place.

Installation

npm install webpack-ruleset

A Webpack config rule can include a child lists of rules as either rules or oneOf attributes. WebpackRuleset will iterate over child rules simmilar to how Webpack iterates over rules when processing an imported resource.

forEach(action)

Iterates over all rules in the rule set. For oneOf child rules, iteration continues until action returns a truthy value.

Update a rule based on a filename that the rule would match.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

ruleSet.forEach(rule => {
    if (rule.loader.includes('babel-loader')) {
        rule.options.babelrc = true;
        return true;
    }
    return false;
});

forAll(action)

Iterates over all rules in the rule set. For oneOf child rules, iteration continues regardless of what value action returns.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);
const HASHED_NAME_RE = /\.?\-?\[(chunk|content)?hash(:\d*)?\]/;

ruleSet.forAll(rule => {
    if (rule.options && rule.options.name && HASHED_NAME_RE.test(rule.options.name)) {
        rule.options.name = formatPath(rule.options.name);
    }
});

Matcher methods

WebpackRuleset also includes a number of matcher methods. Matcher methods take a matcher as their first argument.

The matcher argument can be any of the following:

• A function, which will be passed both the rule and Webpack "normalized" rule and should return true for a matching rule and false for a non-matching rule.

• A resource path string to test rules against. examples: "/full/path/to/something.js" "src/styles.css" - resolved relative to process.cwd() ".css" - treated as "fake_file.css"

• A string suffexed with "-loader". If the matcher is a string ending in "-loader", it will be matched against

• An object with action, loader, or resource and optional loaderType ('pre' or 'post') attributes. Specifying a matcher as an object allows you to specify wether you want to match pre or post loaders.

const action = '.js' // Matches loaders that would match files with the .js extension
const action = {     // Matches pre-loaders that would match files with the .js extension
    loaderType: 'pre',
    resource: '.js',
}

forMatching(matcher, action)

Locate and execute the action on the first matching rule.

Iterates over all rules in the rule set. For oneOf child rules, iteration continues until the matcher matches a rule.

Update a rule based on a filename that the rule would match.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

ruleSet.forMatching('.js', jsRule => {
    jsRule.options.babelrc = true;
});

Update a rule based on the loader name.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

ruleSet.forMatching('css-loader', cssRule => {
    cssRule.options.modules = true;
});

forAllMatching(matcher, action)

Locate and execute the action on all rules that match.

Iterates over all rules in the rule set. For oneOf child rules, iteration continues, even after the matcher matches a rule.

When a oneOf list of rules is encountered, forMatching will call the given action on all matching rules in the oneOf list.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);
const rulesWithHashedNames = r => r.options && r.options.name && isHashedName(r.options.name);

ruleSet.forAllMatching(rulesWithHashedNames, rule => {
    rule.options.name = formatPath(rule.options.name);
});

filter(matcher)

Gathers matching rules into a flat array.

Iterates over all rules in the rule set. For oneOf child rules, iteration continues until the matcher matches a rule.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

const cssLoaders = ruleSet.filter('.css');

filterAll(matcher)

Gathers matching rules into a flat array.

Iterates over all rules in the rule set. For oneOf child rules, iteration continues, even after the matcher matches a rule.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

const cssLoaders = ruleSet.filterAll('.css');

getOneRule(matcher)

Locate a matching rule. Asserts that only one rule matches.

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

const jsRule = ruleSet.getOneRule('.js');
jsRule.options.babelrc = true;

insertRuleBeforeMatch(matcher, insert)

Inserts a new rule before the matching rule. Asserts that only one matching rule is found.

Accepts either a rule object or a function as the second argument. If the insert argument is a function it is called with the matching rule and the parent of the matching rule as parents, otherwise it is inserted as the new rule.

function addCssModuleOption(loader) {
    if (loader.loader && /css\-loader/.test(loader.loader)) {
        return {...loader, options: {...loader.options, modules: true}};
    }
    return loader;
}

const ruleSet = new WebpackRuleset(webpackConfig.module.rules);

// Given a rule set containing a standard css loader, add a css modules rule, with
// css files suffixed with ".global.css" falling through to the existing, non-modules
// css loader.
ruleSet.insertRuleBeforeMatch('.css', globalCssRule => {
    return Object.assign({},
        globalCssRule,
        {
            loader: globalCssRule.loader && globalCssRule.loader.map(addCssModuleOption),
            use: globalCssRule.use && globalCssRule.use.map(addCssModuleOption),
            include: paths.appSrc,
            exclude: /\.global\.css$/,
        }
    );
});

insertRuleAfterMatch(matcher, insert)

Same as insertRuleBeforeMatch, except that the new rule is inserted after the matching rule.