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group-exports.js
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group-exports.js
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import docsUrl from '../docsUrl'
const meta = {
type: 'suggestion',
docs: {
url: docsUrl('group-exports'),
},
}
/* eslint-disable max-len */
const errors = {
ExportNamedDeclaration: 'Multiple named export declarations; consolidate all named exports into a single export declaration',
AssignmentExpression: 'Multiple CommonJS exports; consolidate all exports into a single assignment to `module.exports`',
}
/* eslint-enable max-len */
/**
* Returns an array with names of the properties in the accessor chain for MemberExpression nodes
*
* Example:
*
* `module.exports = {}` => ['module', 'exports']
* `module.exports.property = true` => ['module', 'exports', 'property']
*
* @param {Node} node AST Node (MemberExpression)
* @return {Array} Array with the property names in the chain
* @private
*/
function accessorChain(node) {
const chain = []
do {
chain.unshift(node.property.name)
if (node.object.type === 'Identifier') {
chain.unshift(node.object.name)
break
}
node = node.object
} while (node.type === 'MemberExpression')
return chain
}
function create(context) {
const nodes = {
modules: new Set(),
commonjs: new Set(),
}
return {
ExportNamedDeclaration(node) {
nodes.modules.add(node)
},
AssignmentExpression(node) {
if (node.left.type !== 'MemberExpression') {
return
}
const chain = accessorChain(node.left)
// Assignments to module.exports
// Deeper assignments are ignored since they just modify what's already being exported
// (ie. module.exports.exported.prop = true is ignored)
if (chain[0] === 'module' && chain[1] === 'exports' && chain.length <= 3) {
nodes.commonjs.add(node)
return
}
// Assignments to exports (exports.* = *)
if (chain[0] === 'exports' && chain.length === 2) {
nodes.commonjs.add(node)
return
}
},
'Program:exit': function onExit() {
// Report multiple `export` declarations (ES2015 modules)
if (nodes.modules.size > 1) {
nodes.modules.forEach(node => {
context.report({
node,
message: errors[node.type],
})
})
}
// Report multiple `module.exports` assignments (CommonJS)
if (nodes.commonjs.size > 1) {
nodes.commonjs.forEach(node => {
context.report({
node,
message: errors[node.type],
})
})
}
},
}
}
module.exports = {
meta,
create,
}