A rough history of top-level await discussion at tc39 so far

a-history-of-await.md

• Nov 28th 2012
  • First mention of async / await. In relation to TypeScript
• Jan 30 2014
  • async / await proposal brough to commitee
  • https://github.com/lukehoban/ecmascript-asyncawait
  • Moved to Stage 1
• April 10 2014
  • preview of async / await
  • includes discussion of top-level
  • reserve await

Luke Hoban (LH)
Waldemar Horwat (WH)
Mark Miller (MM)

LH: Questions about whether 'await' should be allowed at top level.  We could add to the module top level grammar, not the script grammar

WH: If it's usable in modules outside async functions, would await be a contextual keyword inside modules? It isn't right now.

MM: That would be a breaking change from ES6.

?: We could disambiguate in grammar.

WH: No. Is x = await(foo) a legacy ES6 function call or an await call?

LH: Good point, we'd need to reserve "await" in modules in ES6.

• June 4th 2014
  • Reserve only await as a keyword in modules.
  • async and module work as contextual keywords because of their position (which can't conflict with variable names).
  • yield is reserved in strict mode, so doesn't need additional reservation.
• July 29th 2014
  • await is a FutureReservedWord when parsing and the syntactic grammar goal symbol is Module
• July 30th 2015
  • Advance Async Functions to Stage 2
  • in depth conversation about TLA
  • DH: No, this needs to be designed in concert with loader. Suggest decoupling to unblock async/await
• Sept 23rd 2015
  • stage 3 approval
  • Discussion of inconsistency with require and "node's" push back on the feature
• July 27 2016
  • top level await is invoked as an edge case to consider in regards to nested import declarations
• July 28 2016
  • Async / Await Stage 4

My thoughts

• Committee has taken action to ensure Top Level Await would be possible
• Scoping it to the module goal may simplify some push back
• It was considered that parts of the loader implementation could be dictated by this feature