Support export * from 'module' ESM syntax

This change adds support for modules that export entities through the
`export * from 'module'` ESM syntax. This resolves issue #31.

Author: jsumners-nr

hook.js

@@ -121,23 +121,63 @@ function createHook (meta) {
 
   const iitmURL = new URL('lib/register.js', meta.url).toString()
   async function getSource (url, context, parentGetSource) {
+    const imports = []
+    const namespaceIds = []
+
     if (hasIitm(url)) {
       const realUrl = deleteIitm(url)
       const exportNames = await getExports(realUrl, context, parentGetSource)
+      const isExportAllLine = /^\* from /
+      const setters = []
+      for (const n of exportNames) {
+        if (isExportAllLine.test(n) === true) {
+          // Encountered a `export * from 'module'` line. Thus, we need to
+          // get all exports from the specified module and shim them into the
+          // current module.
+          const [_, modFile] = n.split('* from ')
+          const modName = Buffer.from(modFile, 'hex') + Date.now()
+          const modUrl = new URL(modFile, url).toString()
+          const innerExports = await getExports(modUrl, context, parentGetSource)
+          const innerSetters = []
+
+          for (const _n of innerExports) {
+            innerSetters.push(`
+            let $${_n} = _.${_n}
+            export { $${_n} as ${_n} }
+            set.${_n} = (v) => {
+              $${_n} = v
+              return true
+            }
+            `)
+          }
+
+          imports.push(`import * as $${modName} from ${JSON.stringify(modUrl)}`)
+          namespaceIds.push(`$${modName}`)
+          setters.push(innerSetters.join('\n'))
+          continue
+        }
+
+        setters.push(`
+        let $${n} = _.${n}
+        export { $${n} as ${n} }
+        set.${n} = (v) => {
+          $${n} = v
+          return true
+        }
+        `)
+      }
+
       return {
         source: `
 import { register } from '${iitmURL}'
 import * as namespace from ${JSON.stringify(url)}
+${imports.join('\n')}
+
+const _ = Object.assign({}, ...[namespace, ${namespaceIds.join(', ')}])
 const set = {}
-${exportNames.map((n) => `
-let $${n} = namespace.${n}
-export { $${n} as ${n} }
-set.${n} = (v) => {
-  $${n} = v
-  return true
-}
-`).join('\n')}
-register(${JSON.stringify(realUrl)}, namespace, set, ${JSON.stringify(specifiers.get(realUrl))})
+
+${setters.join('\n')}
+register(${JSON.stringify(realUrl)}, _, set, ${JSON.stringify(specifiers.get(realUrl))})
 `
       }
     }

lib/get-esm-exports.js

@@ -34,7 +34,7 @@ function getEsmExports (moduleStr) {
         if (node.exported) {
           exportedNames.add(node.exported.name)
         } else {
-          exportedNames.add('*')
+          exportedNames.add(`* from ${node.source.value}`)
         }
         break
       default:

test/fixtures/bundle.mjs

@@ -0,0 +1,3 @@
+import bar from './something.mjs'
+export default bar
+export * from './fantasia.mjs'

test/fixtures/esm-exports.txt

@@ -23,7 +23,7 @@ export default class { /* … */ } //| default
 export default function* () { /* … */ } //| default
 
 // Aggregating modules
-export * from "module-name"; //| *
+export * from "module-name"; //| * from module-name
 export * as name1 from "module-name"; //| name1
 export { name1, /* …, */ nameN } from "module-name"; //| name1,nameN
 export { import1 as name1, import2 as name2, /* …, */ nameN } from "module-name"; //| name1,name2,nameN

test/fixtures/fantasia.mjs

@@ -0,0 +1,5 @@
+export function sayName() {
+  return 'Moon Child'
+}
+
+export const Morla = 'Ancient one'

test/hook/static-import-star.mjs

@@ -0,0 +1,20 @@
+import { strictEqual } from 'assert'
+import Hook from '../../index.js'
+Hook((exports, name) => {
+  if (/bundle\.mjs/.test(name) === false) return
+
+  const bar = exports.default
+  exports.default = function wrappedBar() {
+    return bar() + '-wrapped'
+  }
+
+  const sayName = exports.sayName
+  exports.sayName = function wrappedSayName() {
+    return `Bastion: "${sayName()}"`
+  }
+})
+
+import { default as bar, sayName } from '../fixtures/bundle.mjs'
+
+strictEqual(bar(), '42-wrapped')
+strictEqual(sayName(), 'Bastion: "Moon Child"')