feat(docz-utils): add exports parser to add to Playground scope

#1247

core/docz-utils/src/exports.ts

@@ -0,0 +1,43 @@
+import * as parser from '@babel/parser'
+import traverse from '@babel/traverse'
+import get from 'lodash/get'
+
+const fromDeclarations = (declarations: any = []) =>
+  Array.isArray(declarations) && declarations.length > 0
+    ? declarations.map(declaration => get(declaration, 'id.name'))
+    : []
+
+const traverseOnExports = (fn: (path: any) => any[]) => (node: any) => {
+  try {
+    const ast = parser.parse(node.value, {
+      sourceType: 'module',
+    })
+    let populated: any[] = []
+    traverse(ast, {
+      enter(path: any): void {
+        if (path.isExportDeclaration()) {
+          populated = populated.concat(fn(path))
+          return
+        }
+      },
+    })
+    return populated
+  } catch (err) {
+    return []
+  }
+}
+
+export const getExportsVariables = traverseOnExports(path => {
+  const type = get(path, 'node.declaration.type')
+  switch (type) {
+    case 'VariableDeclaration':
+      return fromDeclarations(get(path, 'node.declaration.declarations', []))
+    case 'FunctionDeclaration':
+      const declaration = get(path, 'node.declaration', false)
+      return fromDeclarations(declaration ? [declaration] : [])
+    case 'Identifier':
+      return get(path, 'node.declaration.name')
+    default:
+      console.error(`Unexpected export type ${type} in docz-utils/exports`)
+  }
+})

core/docz-utils/src/index.ts

@@ -1,6 +1,7 @@
 export * from './ast'
 export * from './fs'
 export * from './imports'
+export * from './exports'
 export * from './jsx'
 export * from './mdast'
 export { format } from './format'