VSC writing own extension, autocompleting with variable and prefix &x_VariableOne - visual-studio-code

Question

How can I tell my extension to look first for &s_?
One solution would be to rename all variable to capital prefix S_, but this is not an option in my scenario.
I am working on an extension for Visual Studio Code(VSC). Variable are defined as followed:
&i_ Var_Six`
&s_ SampelTwo
&...
The implementation in VSC is done by "direct implementation" like that:
let provider1 = vscode.languages.registerCompletionItemProvider({ language: 'test' }, {
provideCompletionItems(document: vscode.TextDocument, position: vscode.Position, token: vscode.CancellationToken, context: vscode.CompletionContext) {
vscode.languages.registerCompletionItemProvider
var completions = new Array();
for (let knownElement of TestVar) {
completions.push(new vscode.CompletionItem(knownElement));
}
return completions;
}
});
context.subscriptions.push(provider1);
Now the problem I have is, that the autocompleting looks first for capital letters but also recognizes the & not as part of the variable.
What I want is that I can start typing "s_" and it would suggest all known variables starting with "&s_".
What VSC actually is suggesting for input “s_” is "i_Var_Six". This is because it looks for the capital letter “S” (camelcase) and the char “ _ ” it does not recognize the char “&” because it is defined as a “word separator”.

Answer 1

i'm not sure why & doesn't work, this is the closest way of implementing it, that i know of.
(read the comments)
import * as vscode from 'vscode';
export function activate(context: vscode.ExtensionContext) {
const TestVar: string[] = ['&_awd', '&_Awd', '&_213', '$_34', '$_23'];
let provider1 = vscode.languages.registerCompletionItemProvider(
{ language: 'plaintext' },
{
provideCompletionItems(
document: vscode.TextDocument,
position: vscode.Position,
token: vscode.CancellationToken,
context: vscode.CompletionContext
) {
var completions = [];
for (let knownElement of TestVar) {
const item = new vscode.CompletionItem(knownElement);
// i added this so that the first & sign gets removed,
// you might want to add a check so that this edit only gets added when the user typed a & sign.
item.additionalTextEdits = [
{ newText: '', range: new vscode.Range(new vscode.Position(position.line, position.character - 1), position), },
];
completions.push(item);
}
return completions;
},
},
'.',
'&' // add this so that the completions get triggered when the user types the & sign.
);
context.subscriptions.push(provider1);
}