fix(async-rewriter2): ensure eval works MONGOSH-665 (#752)

Author: addaleax

packages/async-rewriter2/src/async-writer-babel.spec.ts

@@ -324,6 +324,16 @@ describe('AsyncWriter', () => {
       expect(ret[Symbol.for('@@mongosh.syntheticPromise')]).to.equal(true);
       expect(await ret).to.equal('bar');
     });
+
+    it('works with eval', async() => {
+      implicitlyAsyncFn.resolves('yes');
+      expect(runTranspiledCode('eval("42")')).to.equal(42);
+      expect(runTranspiledCode('let a = 43; eval("a");')).to.equal(43);
+      expect(runTranspiledCode('(() => { let b = 44; return eval("b"); })()')).to.equal(44);
+      expect(await runTranspiledCode(`(() => {
+        globalThis.eval = implicitlyAsyncFn; return eval("b");
+      })()`)).to.equal('yes');
+    });
   });
 
   context('error handling', () => {

packages/async-rewriter2/src/async-writer-babel.ts

@@ -536,9 +536,12 @@ export const makeMaybeAsyncFunctionPlugin = ({ types: t }: { types: typeof Babel
           // If we ever do, replacing all function calls with
           // Function.prototype.call.call(fn, target, ...originalArgs) might be
           // a feasible solution.
+          // Additionally, skip calls to 'eval', since literal calls to it
+          // have semantics that are different from calls to an expressio that
+          // evaluates to 'eval'.
           if (path.parentPath.isCallExpression() &&
               path.key === 'callee' &&
-              path.isMemberExpression()) {
+              (path.isMemberExpression() || (path.isIdentifier() && path.node.name === 'eval'))) {
             return;
           }