New Proposed API checking causes extensions to fail to load when using "import * as vscode" with TypeScript < 3.9

[mwpenny]

• VSCode Version: 1.52.0-insiders (5e350b1)
• OS Version: Windows 10 1809 (OS Build 17763.1518)

Steps to Reproduce:

1. Create an extension (any sample will do) and use a TypeScript version below 3.9
2. Somewhere in the extension, use import * as vscode from "vscode"
3. Try to load the extension. It will fail with the "Proposed API is only available..." error

Does this issue occur when all extensions are disabled?: Yes

Note that this only happens on insiders.

---

Recent changes (c219b06) cause problems for extensions built with old versions of TypeScript (< 3.9). With these old versions

import * as vscode from "vscode"

gets emitted as:

var __importStar = (this && this.__importStar) || function (mod) {
    if (mod && mod.__esModule) return mod;
    var result = {};
    if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) result[k] = mod[k];  // Problem
    result["default"] = mod;
    return result;
};

const vscode = __importStar(require("vscode"));

The line with my added "problem" comment will trigger some getters which include checkProposedApiEnabled() and cause the extension to fail to load with the "Proposed API is only available..." error even though it may never access the relevant properties. Later versions of TypeScript use a getter to defer property access and this isn't a problem.

Technically, I'd call this a TypeScript/tslib bug and not a VSCode bug. It's fixed in later versions of TypeScript (or worked around by changing the imports to import vscode from "vscode"), but I figured you'd like to be made aware since this could cause problems for a number of existing extensions.

[jrieken]

@mwpenny Thanks for the detailed bug report. This is super helpful. What's has changed recently is that I added proposed-api checked for proposed types, e.g we have a new proposed class vscode.TimelineItem and accessing this new type is now also guarded by a proposed API usage check.

[jrieken]

For the November release we should remove the checks for types again

[jrieken]

I believe in addition to an old TS version <3.9 this also needs the following compiler option: "esModuleInterop": true. Without those two, I wasn't able to reproduce... @mwpenny Please confirm my finding.

Anyways, the following extension doesn't actually use proposed API but uses the bogous __importStar-utility and consequently fails to load: ts39-proposed-0.0.3.vsix.zip.

[jrieken]

pushed to master and onto release/1.52