TypeScript Version: 2.8.3, 2.9.0-dev.20180501
Search Terms: name export const
When conditionally assigning to variables that are exported later, the emitted output is inconsistent. In my case I was polyfilling functionality not present in older NodeJS versions through an external module.
The emitted output had a weird order, so when the external module was loaded, I actually exported undefined.
Code
target: es2015
export interface Foo {
method: (...args: any[]) => void;
}
declare function internal(): void;
let exportedFoo: Foo;
declare const condition: boolean;
if (condition) {
// Use native method
exportedFoo = {
method: internal,
};
} else {
// Use polyfilled method
({ foo: exportedFoo } = require("some-module")); // [1]
}
export { exportedFoo as foo }; // [2]Expected behavior:
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
let exportedFoo;
if (condition) {
// Use native method
exportedFoo = {
method: internal,
};
}
else {
// Use polyfilled method
({ foo: exportedFoo } = require("some-module"));
}
exports.foo = exportedFoo;Actual behavior:
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
let exportedFoo;
exports.foo = exportedFoo;
if (condition) {
// Use native method
exports.foo = exportedFoo = {
method: internal,
};
}
else {
// Use polyfilled method
({ foo: exportedFoo } = require("some-module"));
}If condition is true, the export works as expected. Otherwise, exports.foo is undefined.
There are two ways to fix the output:
- changing line
[1] to exportedFoo = require("some-module").foo; but this duplicates the assignment to exports.foo (one per if/else branch)
- changing line
[2] to export const foo = exportedFoo;, this leads to the expected output
The TypeScript Playground seems to get it right however...
Playground Link: https://www.typescriptlang.org/play/#src=export%20interface%20Foo%20%7B%0D%0A%09method%3A%20(...args%3A%20any%5B%5D)%20%3D%3E%20void%3B%0D%0A%7D%0D%0A%0D%0Adeclare%20function%20internal()%3A%20void%3B%0D%0A%0D%0Alet%20exportedFoo%3A%20Foo%3B%0D%0A%0D%0Adeclare%20const%20condition%3A%20boolean%3B%0D%0Aif%20(condition)%20%7B%0D%0A%09%2F%2F%20Use%20native%20method%0D%0A%09exportedFoo%20%3D%20%7B%0D%0A%09%09method%3A%20internal%2C%0D%0A%09%7D%3B%0D%0A%7D%20else%20%7B%0D%0A%09%2F%2F%20Use%20polyfilled%20method%0D%0A%09(%7B%20foo%3A%20exportedFoo%20%7D%20%3D%20require(%22some-module%22))%3B%0D%0A%7D%0D%0A%0D%0Aexport%20%7B%20exportedFoo%20as%20foo%20%7D%3B%0D%0A
Related Issues: ?
TypeScript Version: 2.8.3, 2.9.0-dev.20180501
Search Terms: name export const
When conditionally assigning to variables that are exported later, the emitted output is inconsistent. In my case I was polyfilling functionality not present in older NodeJS versions through an external module.
The emitted output had a weird order, so when the external module was loaded, I actually exported
undefined.Code
target: es2015Expected behavior:
Actual behavior:
If
conditionis true, the export works as expected. Otherwise,exports.fooisundefined.There are two ways to fix the output:
[1]toexportedFoo = require("some-module").foo;but this duplicates the assignment toexports.foo(one per if/else branch)[2]toexport const foo = exportedFoo;, this leads to the expected outputThe TypeScript Playground seems to get it right however...
Playground Link: https://www.typescriptlang.org/play/#src=export%20interface%20Foo%20%7B%0D%0A%09method%3A%20(...args%3A%20any%5B%5D)%20%3D%3E%20void%3B%0D%0A%7D%0D%0A%0D%0Adeclare%20function%20internal()%3A%20void%3B%0D%0A%0D%0Alet%20exportedFoo%3A%20Foo%3B%0D%0A%0D%0Adeclare%20const%20condition%3A%20boolean%3B%0D%0Aif%20(condition)%20%7B%0D%0A%09%2F%2F%20Use%20native%20method%0D%0A%09exportedFoo%20%3D%20%7B%0D%0A%09%09method%3A%20internal%2C%0D%0A%09%7D%3B%0D%0A%7D%20else%20%7B%0D%0A%09%2F%2F%20Use%20polyfilled%20method%0D%0A%09(%7B%20foo%3A%20exportedFoo%20%7D%20%3D%20require(%22some-module%22))%3B%0D%0A%7D%0D%0A%0D%0Aexport%20%7B%20exportedFoo%20as%20foo%20%7D%3B%0D%0A
Related Issues: ?