RangeError: Maximum call stack size exceeded with recent vscode.html builtin extension

[marcdumais-work]

Bug Description:

Since recently, vscode builtin "vscode.html" contributes a snippet, which trips Theia's snippet parser, throwing it into infinite recursion. The snippet appeared after v1.70.2, and we are noticing it for the first time with unreleased v1.72.2. This extension is tiny, contributing only a Textmate grammar and a snippet.

Here is the parser that goes into recursive loop when dealing with the contributed snippet:

theia/packages/monaco/src/browser/monaco-snippet-suggest-provider.ts

Lines 194 to 202 in 83b726e

	protected parseSnippets(snippets: JsonSerializedSnippets | undefined, accept: (name: string, snippet: JsonSerializedSnippet) => void): void {
	for (const [name, scopeOrTemplate] of Object.entries(snippets ?? {})) {
	if (JsonSerializedSnippet.is(scopeOrTemplate)) {
	accept(name, scopeOrTemplate);
	} else {
	this.parseSnippets(scopeOrTemplate, accept);
	}
	}
	}

2023-04-19T16:39:20.368Z root INFO Changed application state from 'attached_shell' to 'initialized_layout'.
2023-04-19T16:39:20.440Z root INFO [a237a147-9f5a-4f0f-99d3-b1ff74376554] Sync of 2 plugins: 127.0 ms [Finished 2.093 s after frontend start]
2023-04-19T16:39:20.440Z root INFO [a237a147-9f5a-4f0f-99d3-b1ff74376554] Loading plugin contributions
2023-04-19T16:39:20.440Z root INFO [a237a147-9f5a-4f0f-99d3-b1ff74376554] Load contributions of 2 plugins: 21.0 ms [Finished 2.114 s after frontend start]
2023-04-19T16:39:20.481Z root WARN [a237a147-9f5a-4f0f-99d3-b1ff74376554][vscode.html]: Language for 'source.css' not found.
2023-04-19T16:39:20.482Z root WARN [a237a147-9f5a-4f0f-99d3-b1ff74376554][vscode.html]: Language for 'source.js' not found.
2023-04-19T16:39:20.482Z root WARN [a237a147-9f5a-4f0f-99d3-b1ff74376554][vscode.html]: Language for 'source.python' not found.
2023-04-19T16:39:20.482Z root WARN [a237a147-9f5a-4f0f-99d3-b1ff74376554][vscode.html]: Language for 'source.smarty' not found.
2023-04-19T16:39:20.526Z root ERROR RangeError: Maximum call stack size exceeded
    at Array.values (<anonymous>)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3122:54)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)
    at MonacoSnippetSuggestProvider.parseSnippets (http://localhost:3000/packages_monaco_lib_browser_monaco-frontend-module_js.js:3127:22)

Steps to Reproduce:

1. Build the example application, browser or Electron, from the master branch
2. Delete all extensions from folder ./plugins/. Unzip html-1.72.1.zip into it:
   html-1.72.1.zip
3. Start example app. You should see a similar as above "RangeError: Maximum call stack size exceeded" exception

Additional Information

• Operating System:
• Theia Version: