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export.js
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export.js
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import ExportMap, { recursivePatternCapture } from '../ExportMap'
import docsUrl from '../docsUrl'
import includes from 'array-includes'
/*
Notes on TypeScript namespaces aka TSModuleDeclaration:
There are two forms:
- active namespaces: namespace Foo {} / module Foo {}
- ambient modules; declare module "eslint-plugin-import" {}
active namespaces:
- cannot contain a default export
- cannot contain an export all
- cannot contain a multi name export (export { a, b })
- can have active namespaces nested within them
ambient namespaces:
- can only be defined in .d.ts files
- cannot be nested within active namespaces
- have no other restrictions
*/
const rootProgram = 'root'
const tsTypePrefix = 'type:'
/**
* Detect function overloads like:
* ```ts
* export function foo(a: number);
* export function foo(a: string);
* export function foo(a: number|string) { return a; }
* ```
* @param {Set<Object>} nodes
* @returns {boolean}
*/
function isTypescriptFunctionOverloads(nodes) {
const types = new Set(Array.from(nodes, node => node.parent.type))
return (
types.has('TSDeclareFunction') &&
(types.size === 1 || types.size === 2 && types.has('FunctionDeclaration'))
)
}
module.exports = {
meta: {
type: 'problem',
docs: {
url: docsUrl('export'),
},
},
create: function (context) {
const namespace = new Map([[rootProgram, new Map()]])
function addNamed(name, node, parent, isType) {
if (!namespace.has(parent)) {
namespace.set(parent, new Map())
}
const named = namespace.get(parent)
const key = isType ? `${tsTypePrefix}${name}` : name
let nodes = named.get(key)
if (nodes == null) {
nodes = new Set()
named.set(key, nodes)
}
nodes.add(node)
}
function getParent(node) {
if (node.parent && node.parent.type === 'TSModuleBlock') {
return node.parent.parent
}
// just in case somehow a non-ts namespace export declaration isn't directly
// parented to the root Program node
return rootProgram
}
return {
'ExportDefaultDeclaration': (node) => addNamed('default', node, getParent(node)),
'ExportSpecifier': (node) => addNamed(node.exported.name, node.exported, getParent(node)),
'ExportNamedDeclaration': function (node) {
if (node.declaration == null) return
const parent = getParent(node)
// support for old TypeScript versions
const isTypeVariableDecl = node.declaration.kind === 'type'
if (node.declaration.id != null) {
if (includes([
'TSTypeAliasDeclaration',
'TSInterfaceDeclaration',
], node.declaration.type)) {
addNamed(node.declaration.id.name, node.declaration.id, parent, true)
} else {
addNamed(node.declaration.id.name, node.declaration.id, parent, isTypeVariableDecl)
}
}
if (node.declaration.declarations != null) {
for (let declaration of node.declaration.declarations) {
recursivePatternCapture(declaration.id, v =>
addNamed(v.name, v, parent, isTypeVariableDecl))
}
}
},
'ExportAllDeclaration': function (node) {
if (node.source == null) return // not sure if this is ever true
const remoteExports = ExportMap.get(node.source.value, context)
if (remoteExports == null) return
if (remoteExports.errors.length) {
remoteExports.reportErrors(context, node)
return
}
const parent = getParent(node)
let any = false
remoteExports.forEach((v, name) =>
name !== 'default' &&
(any = true) && // poor man's filter
addNamed(name, node, parent))
if (!any) {
context.report(node.source,
`No named exports found in module '${node.source.value}'.`)
}
},
'Program:exit': function () {
for (let [, named] of namespace) {
for (let [name, nodes] of named) {
if (nodes.size <= 1) continue
if (isTypescriptFunctionOverloads(nodes)) continue
for (let node of nodes) {
if (name === 'default') {
context.report(node, 'Multiple default exports.')
} else {
context.report(
node,
`Multiple exports of name '${name.replace(tsTypePrefix, '')}'.`
)
}
}
}
}
},
}
},
}