__self and __source no longer added in development mode using classic runtime

[billyjanitsch]

Current behavior:

This is actually an issue in Babel, but it was caused by babel/babel#12253 and manifests when using the Emotion preset so I decided to file it here.

Given the following Babel config:

{
  "presets": [
    ["@babel/preset-react", { "development": true }],
    "@emotion/babel-preset-css-prop"
  ]
}

And the following source code:

import * as React from "react";

export default function Foo() {
  return <div />;
}

Using @babel/preset-react@7.12.7 (and its transitive deps that were available as part of the 7.12.7 Babel release), the code would transpile to:

var _jsxFileName = "/Users/billy/work/emotion-classic/index.js";
import * as React from "react";
import { jsx as ___EmotionJSX } from "@emotion/react";
export default function Foo() {
  return ___EmotionJSX("div", {
    __self: this,
    __source: {
      fileName: _jsxFileName,
      lineNumber: 4,
      columnNumber: 10
    }
  });
}

With @babel/preset-react@7.12.10, it transpiles to:

var _jsxFileName = "/Users/billy/work/emotion-classic/index.js";
import * as React from "react";
import { jsx as ___EmotionJSX } from "@emotion/react";
export default function Foo() {
  return ___EmotionJSX("div", null);
}

It's interesting because it seems to be the opposite bug as babel/babel#12475.

It might be an ordering issue, if the new transform is injecting the dev stuff at a different point in the Babel lifecycle than the old one. In any case, I wouldn't expect an observable behavioral change in a patch release.

To reproduce:

Reproducing repo is here. Clone and run npm it on either of the two commits to observe the two behaviors.

Expected behavior:

Adding development: true to the React preset config should include the dev transforms.

Environment information:

• react version: n/a
• @emotion/react version: n/a
• @emotion/babel-preset-css-prop: 11.0.0

[Andarist]

Thanks for the detailed repro and stalking my latest PRs to Babel I'll try to look into this asap

[billyjanitsch]

Haha I swear I wasn't stalking! I just noticed it while upgrading our preset deps: kensho-technologies/babel-preset#102.

There's actually a second observable change in the Babel PR, btw. When setting runtime: 'classic', it's now an error to set importSource. Previously, the importSource value was just ignored. You can see the necessary change in the PR I linked. Not sure if this change was intentional?

[Andarist]

Closing here as ive prepared a PR to Babel that should fix this: babel/babel#12495

As to the other issue - could u raise it in Babel and ping me there? I will try to handle it as well