Cannot set property on #<Object> which has only a getter

[mjbvz]

TypeScript Version: 4.0.0-dev.20200622

Search Terms:

Repo

1. In the VS Code code base
2. Revert this change in grid.ts
3. Recompile VS Code (yarn run watch
4. Start VS Code

Bug:

VS Code doesn't start due to the following exception

/Users/matb/projects/vscode/out/bootstrap-window.js:215 TypeError: Cannot set property GridViewSizing of #<Object> which has only a getter
    at Object.<anonymous> (/Users/matb/projects/vscode/out/vs/base/browser/ui/grid/grid.js:136)
    at Function.Module._invokeFactory (/Users/matb/projects/vscode/out/vs/loader.js:1040)
    at Module.complete (/Users/matb/projects/vscode/out/vs/loader.js:1050)
    at ModuleManager._onModuleComplete (/Users/matb/projects/vscode/out/vs/loader.js:1671)
...

This is triggered on a line that looks like:

    exports.GridViewSizing = Sizing;

[mjbvz]

@RyanCavanaugh This seems like a regression from 4.0.0-dev.20200615. Possibly related to #38809?

[weswigham]

Wow, so it looks like there's a bug in our namespace export emit - namely, export namespace Sizing is adopting the reexport from
export { Orientation, Sizing as GridViewSizing, IViewSize, orthogonal, LayoutPriority } from './gridview'; - there shouldn't be a exports.GridViewSizing = Sizing;, since the local Sizing namespace isn't exported as GridViewSizing. Here's a minimal repro:

// @filename: gridview.ts
export type Sizing = any;
export namespace Sizing {
	export const Distribute = { type: 'distribute' };
}
// @filename: index.ts
export { Sizing as GridViewSizing } from './gridview';
export namespace Sizing {
	export const Distribute = { type: 'distribute' };
}

I'm working on it now.