Add FLOW_RUNTIME=namespace configuration

This is a:

• Bug Report
• Feature Request
• Question
• Other

Which concerns:

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

---

What is the current behaviour?

The current implementation of babel-plugin-flow-runtime allows configuration that either inlines the assertions or skips them at a compile them. This is good enough for developing a library that uses flow-runtime.

const add = (a: number, b: number): number => a + b;

is transformed to:

import t from 'flow-runtime';
const add = (a, b) => {
  let _aType = t.number();
  let _bType = t.number();
  const _returnType = t.return(t.number());
  t.param('a', _aType).assert(a);
  t.param('b', _bType).assert(b);
  return _returnType.assert(a + b);
};

However, it limits library author’s ability to distribute code with flow-runtime assertions. I do not want to use dependencies in production that have inlined flow-runtime assertions (for performance reasons).

---

What is the expected behaviour?

I’d like babel-plugin-flow-runtime to accept a configuration that inlines a conditional runtime assertion, e.g.

{
  "plugins": [["flow-runtime", {
    "assert": "applaudience:showtime-api"
  }]]
}

would produce code:

import t from 'flow-runtime';
const add = (a, b) => {
  if (process.env.FLOW_RUNTIME && process.env.FLOW_RUNTIME.startsWith('applaudience:showtime-api')) {
    let _aType = t.number();
    let _bType = t.number();
    const _returnType = t.return(t.number());
    t.param('a', _aType).assert(a);
    t.param('b', _bType).assert(b);
    return _returnType.assert(a + b);
  } else {
    return a + b;
  }
};

This is a mock implementation. A real-life implementation would follow the debug conventions.

This way, I could distribute all my codes with inlined flow-runtime assertions that users could enable when debugging issues the same way that debug is being used, e.g.

FLOW_RUNTIME=applaudience:* node ./index.js

would enable runtime type assertions for all dependencies under the “applaudience” namespace.

---

[phpnode]

here we go: https://github.com/codemix/babel-plugin-conditional

[Amin-Medbelle]

@phpnode Have you seen this article? It pretty much resolves the conditional plugin issues.