VSCode preselects a wrong CompletionItem if there are multiple CompletionItem having preselect=true

[HaoboGu]

• VSCode Version: 1.45.1
• OS Version: Darwin x64 19.4.0

Steps to Reproduce:

1. Add an extension which generates multiple completion items with preselect=true

import * as vscode from 'vscode';

export function activate(context: vscode.ExtensionContext) {
	let sel:vscode.DocumentSelector = { scheme: 'file' };
	let LanguageServerProvider = vscode.languages.registerCompletionItemProvider(sel, { 
		provideCompletionItems(document: vscode.TextDocument, position: vscode.Position) {
			let completionResult: vscode.CompletionItem[] = []
			let a = new vscode.CompletionItem("a");
			a.preselect = true;
			a.filterText = "a"
			a.sortText = "0";
			let b = new vscode.CompletionItem("b");
			b.preselect = true;
			b.filterText = "b"
			b.sortText = "00";
			let c = new vscode.CompletionItem("c");
			c.preselect = true;
			c.filterText = "c"
			c.sortText = "000";
			completionResult.push(a, b, c);
			return completionResult
		}
	}, " ", ".");
	context.subscriptions.push(LanguageServerProvider);
}

export function deactivate() {}

2. Trigger auto-completion, vscode would always choose b as the preselected item:

Does this issue occur when all extensions are disabled?: No - it requires a completion extension

Expected behavior:
Vscode should preselect a

Possible cause:

vscode/src/vs/editor/contrib/suggest/suggestMemory.ts

Lines 24 to 41 in 7f49bf1

	select(model: ITextModel, pos: IPosition, items: CompletionItem[]): number {
	if (items.length === 0) {
	return 0;
	}
	let topScore = items[0].score[0];
	for (let i = 1; i < items.length; i++) {
	const { score, completion: suggestion } = items[i];
	if (score[0] !== topScore) {
	// stop when leaving the group of top matches
	break;
	}
	if (suggestion.preselect) {
	// stop when seeing an auto-select-item
	return i;
	}
	}
	return 0;
	}