Looking through the ESLint code, I can't find where this sort of stuff is implemented:

':function': (node: TSESTree.Node) => {
  onEnterFunction(node as TSESTree.FunctionLike);
},
':function:exit'(node: TSESTree.Node) {
  onLeaveFunction(node as TSESTree.FunctionLike);
},

'*'(node: TSESTree.Node) {
  if (nestingNodes.has(node)) {
    nesting  ;
  }
},
'*:exit'(node: TSESTree.Node) {
  if (nestingNodes.has(node)) {
    nesting--;
    nestingNodes.delete(node);
  }
},

Specifically the "matcher" keys like *:exit, and I've seen much more complicated CSS-selector-like expressions. Where in the ESLint source is the handler for these implemented?

I would like to see how it's implemented to implement on my own.

CodePudding user response：

It looks like it is implemented in esquery.

function matches(node, selector, ancestry, options) {
    if (!selector) { return true; }
    if (!node) { return false; }
    if (!ancestry) { ancestry = []; }

    switch(selector.type) {
        case 'wildcard':
            return true;

        case 'identifier':
            return selector.value.toLowerCase() === node.type.toLowerCase();

        case 'field': {
            const path = selector.name.split('.');
            const ancestor = ancestry[path.length - 1];
            return inPath(node, ancestor, path);

        }
        case 'matches':
            for (const sel of selector.selectors) {
                if (matches(node, sel, ancestry, options)) { return true; }
            }
            return false;

        case 'compound':
            for (const sel of selector.selectors) {
                if (!matches(node, sel, ancestry, options)) { return false; }
            }
            return true;

        case 'not':
            for (const sel of selector.selectors) {
                if (matches(node, sel, ancestry, options)) { return false; }
            }
            return true;

        case 'has': {
            const collector = [];
            for (const sel of selector.selectors) {
                const a = [];
                estraverse.traverse(node, {
                    enter (node, parent) {
                        if (parent != null) { a.unshift(parent); }
                        if (matches(node, sel, a, options)) {
                            collector.push(node);
                        }
                    },
                    leave () { a.shift(); },
                    keys: options && options.visitorKeys,
                    fallback: options && options.fallback || 'iteration'
                });
            }
            return collector.length !== 0;

        }
        case 'child':
            if (matches(node, selector.right, ancestry, options)) {
                return matches(ancestry[0], selector.left, ancestry.slice(1), options);
            }
            return false;

        case 'descendant':
            if (matches(node, selector.right, ancestry, options)) {
                for (let i = 0, l = ancestry.length; i < l;   i) {
                    if (matches(ancestry[i], selector.left, ancestry.slice(i   1), options)) {
                        return true;
                    }
                }
            }
            return false;

        case 'attribute': {
            const p = getPath(node, selector.name);
            switch (selector.operator) {
                case void 0:
                    return p != null;
                case '=':
                    switch (selector.value.type) {
                        case 'regexp': return typeof p === 'string' && selector.value.value.test(p);
                        case 'literal': return `${selector.value.value}` === `${p}`;
                        case 'type': return selector.value.value === typeof p;
                    }
                    throw new Error(`Unknown selector value type: ${selector.value.type}`);
                case '!=':
                    switch (selector.value.type) {
                        case 'regexp': return !selector.value.value.test(p);
                        case 'literal': return `${selector.value.value}` !== `${p}`;
                        case 'type': return selector.value.value !== typeof p;
                    }
                    throw new Error(`Unknown selector value type: ${selector.value.type}`);
                case '<=': return p <= selector.value.value;
                case '<': return p < selector.value.value;
                case '>': return p > selector.value.value;
                case '>=': return p >= selector.value.value;
            }
            throw new Error(`Unknown operator: ${selector.operator}`);
        }
        case 'sibling':
            return matches(node, selector.right, ancestry, options) &&
                sibling(node, selector.left, ancestry, LEFT_SIDE, options) ||
                selector.left.subject &&
                matches(node, selector.left, ancestry, options) &&
                sibling(node, selector.right, ancestry, RIGHT_SIDE, options);
        case 'adjacent':
            return matches(node, selector.right, ancestry, options) &&
                adjacent(node, selector.left, ancestry, LEFT_SIDE, options) ||
                selector.right.subject &&
                matches(node, selector.left, ancestry, options) &&
                adjacent(node, selector.right, ancestry, RIGHT_SIDE, options);

        case 'nth-child':
            return matches(node, selector.right, ancestry, options) &&
                nthChild(node, ancestry, function () {
                    return selector.index.value - 1;
                }, options);

        case 'nth-last-child':
            return matches(node, selector.right, ancestry, options) &&
                nthChild(node, ancestry, function (length) {
                    return length - selector.index.value;
                }, options);

        case 'class':
            switch(selector.name.toLowerCase()){
                case 'statement':
                    if(node.type.slice(-9) === 'Statement') return true;
                    // fallthrough: interface Declaration <: Statement { }
                case 'declaration':
                    return node.type.slice(-11) === 'Declaration';
                case 'pattern':
                    if(node.type.slice(-7) === 'Pattern') return true;
                    // fallthrough: interface Expression <: Node, Pattern { }
                case 'expression':
                    return node.type.slice(-10) === 'Expression' ||
                        node.type.slice(-7) === 'Literal' ||
                        (
                            node.type === 'Identifier' &&
                            (ancestry.length === 0 || ancestry[0].type !== 'MetaProperty')
                        ) ||
                        node.type === 'MetaProperty';
                case 'function':
                    return node.type === 'FunctionDeclaration' ||
                        node.type === 'FunctionExpression' ||
                        node.type === 'ArrowFunctionExpression';
            }
            throw new Error(`Unknown class name: ${selector.name}`);
    }

    throw new Error(`Unknown selector type: ${selector.type}`);
}