export from should be passed through _interopRequireDefault

[forivall]

The two source files should generate equivalent imports transformation:

Sandbox

import foo from 'bar'
export { foo }

Sandbox

export { default as foo } from 'bar'

The output is identical with babel, and typescript uses its __importDefault in a different order. Sucrase only applies the _interopRequireDefault in the first example.

IMO, the sucrase transformed code should be as follows:

"use strict";Object.defineProperty(exports, "__esModule", {value: true}); function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; } function _createNamedExportFrom(obj, localName, importedName) { Object.defineProperty(exports, localName, {enumerable: true, configurable: true, get: () => obj[importedName]}); }
var _bar = require('bar'); var _bar2 = _interopRequireDefault(_bar); _createNamedExportFrom(_bar2, 'foo', 'default');

(unless enableLegacyTypeScriptModuleInterop is enabled, obvi)

[alangpierce]

Hi @forivall , thanks for reporting! I agree that this is a bug. To be clear, the impact is that the re-export won't work correctly if "bar" is a regular CJS module, e.g. if it has a line like module.exports = "Hello";. I'm a bit busy at the moment, but may be able to find some time for it, or a PR would be welcome. There was already a similar fix in #619 (which is why the two-line version works), so the fix would probably be something similar.

(A separate but related issue is whether to use live bindings vs a plain export assignment for the two-line version. That came up in #715 (comment) , and I have some hesitation with switching the behavior due to possible backcompat issues, though it might be fine.)

[forivall]

No worries on timing. The issue doesnt impact anything at the moment, I just noticed when making notes of all of the quirks of sucrase that I need to be aware of.

As far as the transitive binding, I think the export {...} from should use live bindings, since that's what tsc does (even for legacy interop), but tsc doesn't do live bindings for the 2 line export.

Ideally, there should be flags for this, although, that does introduce maintenance burden.