Can I Add a Completions (Intellisense) File to a Language Support Extension? - autocomplete

Question

I am developing a language support extension for VS Code by converting a Sublime tmBundle. I am using the bundle from siteleaf/liquid-syntax-mode. I have successfully included the following using yo code options 4 & 5 and combining the output:
Syntax File (.tmLanguage)
Snippets (.sublime-snippet)
What I would like to do is add autocomplete/Intellisense support by importing the .sublime-completions file, either directly or by rewriting it somehow.
Is it even possible to add items to the autocomplete/Intellisense in VS Code?

Answer 1

It looks like it is possible if I create a Language Server extension. From the site:
The first interesting feature a language server usually implements is validation of documents. In that sense, even a linter counts as a language server and in VS Code linters are usually implemented as language servers (see eslint and jshint for examples). But there is more to language servers. They can provide code complete, Find All References or Go To Definition. The example code below adds code completion to the server. It simply proposes the two words 'TypeScript' and 'JavaScript'.
And some sample code:
// This handler provides the initial list of the completion items.
connection.onCompletion((textDocumentPosition: TextDocumentPositionParams): CompletionItem[] => {
// The pass parameter contains the position of the text document in
// which code complete got requested. For the example we ignore this
// info and always provide the same completion items.
return [
{
label: 'TypeScript',
kind: CompletionItemKind.Text,
data: 1
},
{
label: 'JavaScript',
kind: CompletionItemKind.Text,
data: 2
}
]
});
// This handler resolve additional information for the item selected in
// the completion list.
connection.onCompletionResolve((item: CompletionItem): CompletionItem => {
if (item.data === 1) {
item.detail = 'TypeScript details',
item.documentation = 'TypeScript documentation'
} else if (item.data === 2) {
item.detail = 'JavaScript details',
item.documentation = 'JavaScript documentation'
}
return item;
});