Runtime types generated when not used

[skeggse]

This is a:

• [x] Bug Report
• [ ] Feature Request
• [ ] Question
• [ ] Other

Which concerns:

• [ ] flow-runtime
• [x] babel-plugin-flow-runtime
• [ ] flow-runtime-validators
• [ ] flow-runtime-mobx
• [ ] flow-config-parser
• [ ] The documentation website

Relates to #202.

---

What is the current behaviour?

Transforming a barebones file that imports types from a dependency causes that dependency to get imported, even if the types aren't used - and the runtime types aren't available.

In this particular case, I'm passing the annotate: false option to babel-plugin-flow-runtime to try and work around #202.

import type { APIGatewayEvent, Context, ProxyResult } from 'flow-aws-lambda';

import { load } from './load';

export function handle(evt: APIGatewayEvent<any>, ctx: Context): Promise<ProxyResult> {
  return load(evt, ctx);
}

Babel generates the following from the above file, which imports the flow-aws-lambda package; this package exports types, but does not export runtime types. I could try and use @babel/register to work around this, but for my purposes I'd like to have babel spit out code that's directly executed by node, for auditing and deployment purposes.

"use strict";

exports.handle = handle;

var _flowAwsLambda = require("flow-aws-lambda");

var _load = require("./load");

var _flowRuntime = _interopRequireDefault(require("flow-runtime"));

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

const APIGatewayEvent = _flowRuntime.default.tdz(() => _flowAwsLambda.APIGatewayEvent);

const Context = _flowRuntime.default.tdz(() => _flowAwsLambda.Context);

const ProxyResult = _flowRuntime.default.tdz(() => _flowAwsLambda.ProxyResult);

function handle(evt, ctx) {
  return (0, _load.load)(evt, ctx);
}

---

What is the expected behaviour?

Generate only those runtime types that actually get used (in this case, none), and omit the associated imports if any:

--- dist/index.js
+++ dist/index.js
@@ -1,8 +1,6 @@
 "use strict";
 
 exports.handle = handle;
-
-var _flowAwsLambda = require("flow-aws-lambda");
 
 var _load = require("./load");
 
@@ -10,12 +8,6 @@
 
 function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
 
-const APIGatewayEvent = _flowRuntime.default.tdz(() => _flowAwsLambda.APIGatewayEvent);
-
-const Context = _flowRuntime.default.tdz(() => _flowAwsLambda.Context);
-
-const ProxyResult = _flowRuntime.default.tdz(() => _flowAwsLambda.ProxyResult);
-
 function handle(evt, ctx) {
   return (0, _load.load)(evt, ctx);
 }

Along these lines, it'd also be nice to be able to disable annotations for a specific function, but I think for now disabling annotations just for specific files in babel's rc file will suffice.

---

Which package versions are you using?

• [email protected]
• [email protected]

[gajus]

I can reward a bounty to this issue if you are available to work.

[skeggse]

@gajus I might be able to find time to work on this, though I have looked at the code, and I'm not sure I'll have enough context to implement a solution. I'm somewhat partial to the workaround in #240 for my own use-cases, but I don't think it's a great solution for #239 for everyone.

[gajus]

What is a good amount to reward to this bounty?

[skeggse]

I'm very unsure about how I'd evaluate that, sorry.