Formatting of await misses parentheses

[skeggse]

The following two functions differ, in that one awaits the result of a() while one dereferences b off of a's return value and then awaits that value.

async function fnA() {
  return await a().b;
}
async function fnB() {
  return (await a()).b;
}

The AST for the latter produces the former in recast:

const recast = require('recast');
const {builders} = require('ast-types');

console.log(
  recast.print(
    builders.functionDeclaration(
      builders.identifier('fnB'),
      [],
      builders.blockStatement([
        builders.returnStatement(
          builders.memberExpression(
            builders.awaitExpression(builders.callExpression(builders.identifier('a'), [])),
            builders.identifier('b')
          )
        ),
      ])
    )
  ).code
);

// produces

function fnB() {
    return await a().b;
}

Moreover, I can't find a workaround for this bug - I'd like to explicitly wrap the await expression in parentheses but don't see a way to do so. EDIT: I missed the ParenthesizedExpression type.

[kindy]

seems escodegen works fine for await.

[benjamn]

This is definitely a bug, since Recast takes responsibility for inserting parentheses when necessary to preserve AST structure. There are ways to force parentheses, but that's not the recommended way of handling this. The Recast printer should just get it right.

[skeggse]

I opened a possible fix for this benjamn/ast-types#349 - does that seem like the right approach?

[splitice]

Just hit this bug as well.

The obvious workaround for those who find this is to throw a function around the await as function calls are correctly handled with awaits.

[jedwards1211]

I'm seeing a similar issue when wrapping a ConditionalExpression in an AwaitExpression. Like OP I was able to workaround by using ParenthesizedExpression.

[conartist6]

I've published a PR which should fix these and other issues with parens and also expands relevant test coverage.

@skeggse I believe it improves on your PR by eliminating parens in places where they are irrelevant, e.g. new Class(await args), which would otherwise print as new Class((await args)).