Check exported bindings are defined (#9589)

* Check exported bindings are defined

* Add tests

* Update flow whitelist

* Add tests for builtins

packages/babel-parser/src/parser/statement.js

@@ -49,6 +49,14 @@ export default class StatementParser extends ExpressionParser {
 
     this.parseBlockBody(program, true, true, tt.eof);
 
+    if (this.inModule && this.scope.undefinedExports.size > 0) {
+      for (const [name] of Array.from(this.scope.undefinedExports)) {
+        const pos = this.scope.undefinedExports.get(name);
+        // $FlowIssue
+        this.raise(pos, `Export '${name}' is not defined`);
+      }
+    }
+
     file.program = this.finishNode(program, "Program");
     file.comments = this.state.comments;
 
@@ -1631,7 +1639,7 @@ export default class StatementParser extends ExpressionParser {
     }
 
     if (isFromRequired || hasSpecifiers || hasDeclaration) {
-      this.checkExport(node, true);
+      this.checkExport(node, true, false, !!node.source);
       return this.finishNode(node, "ExportNamedDeclaration");
     }
 
@@ -1845,8 +1853,9 @@ export default class StatementParser extends ExpressionParser {
 
   checkExport(
     node: N.ExportNamedDeclaration,
-    checkNames: ?boolean,
+    checkNames?: boolean,
     isDefault?: boolean,
+    isFrom?: boolean,
   ): void {
     if (checkNames) {
       // Check for duplicate exports
@@ -1857,6 +1866,11 @@ export default class StatementParser extends ExpressionParser {
         // Named exports
         for (const specifier of node.specifiers) {
           this.checkDuplicateExports(specifier, specifier.exported.name);
+          // check if export is defined
+          // $FlowIgnore
+          if (!isFrom && specifier.local) {
+            this.scope.checkLocalExport(specifier.local);
+          }
         }
       } else if (node.declaration) {
         // Exported declarations

packages/babel-parser/src/types.js

@@ -831,6 +831,7 @@ export type ExportNamedDeclaration = NodeBase & {
 export type ExportSpecifier = NodeBase & {
   type: "ExportSpecifier",
   exported: Identifier,
+  local: Identifier,
 };
 
 export type ExportDefaultSpecifier = NodeBase & {

packages/babel-parser/src/util/scope.js

@@ -16,6 +16,7 @@ import {
   type BindingTypes,
   SCOPE_CLASS,
 } from "./scopeflags";
+import * as N from "../types";
 
 // Start an AST node, attaching a start offset.
 class Scope {
@@ -40,6 +41,7 @@ export default class ScopeHandler {
   scopeStack: Array<Scope> = [];
   raise: raiseFunction;
   inModule: boolean;
+  undefinedExports: Map<string, number> = new Map();
 
   constructor(raise: raiseFunction, inModule: boolean) {
     this.raise = raise;
@@ -95,6 +97,9 @@ export default class ScopeHandler {
         scope.functions.indexOf(name) > -1 ||
         scope.var.indexOf(name) > -1;
       scope.lexical.push(name);
+      if (this.inModule && scope.flags & SCOPE_PROGRAM) {
+        this.undefinedExports.delete(name);
+      }
     } else if (bindingType === BIND_SIMPLE_CATCH) {
       const scope = this.currentScope();
       scope.lexical.push(name);
@@ -122,6 +127,10 @@ export default class ScopeHandler {
         }
         scope.var.push(name);
 
+        if (this.inModule && scope.flags & SCOPE_PROGRAM) {
+          this.undefinedExports.delete(name);
+        }
+
         if (scope.flags & SCOPE_VAR) break;
       }
     }
@@ -130,6 +139,16 @@ export default class ScopeHandler {
     }
   }
 
+  checkLocalExport(id: N.Identifier) {
+    // scope.functions must be empty as Module code is always strict.
+    if (
+      this.scopeStack[0].lexical.indexOf(id.name) === -1 &&
+      this.scopeStack[0].var.indexOf(id.name) === -1
+    ) {
+      this.undefinedExports.set(id.name, id.start);
+    }
+  }
+
   currentScope(): Scope {
     return this.scopeStack[this.scopeStack.length - 1];
   }