open method
Opens uri with text. languageId defaults to the language inferred
from the URI extension (falling back to dart).
Implementation
void open(String uri, String text, {String? languageId}) {
_versions[uri] = 1;
_client.didOpen(
uri,
text,
languageId: languageId ?? Analyzer.languageOf(uri) ?? 'dart',
version: 1,
);
}