feat: add simple auto-complete for keywords and built-in types

src/extension.ts

@@ -1,7 +1,71 @@
 import * as vscode from 'vscode';
 
+const builtinTypes = [
+  "u8",
+  "u16",
+  "u32",
+  "u64",
+  "s8",
+  "s16",
+  "s32",
+  "s64",
+  "float32",
+  "float64",
+  "char",
+  "bool",
+  "string",
+  "tuple",
+  "list",
+  "option",
+  "result",
+  "borrow",
+];
+
+const keywords = [
+  "_",
+  "as",
+  "constructor",
+  "enum",
+  "export",
+  "flags",
+  "func",
+  "import",
+  "include",
+  "interface",
+  "package",
+  "record",
+  "resource",
+  "static",
+  "type",
+  "union",
+  "use",
+  "variant",
+  "with",
+  "world",
+];
+
+const staticCompletions = new vscode.CompletionList([
+  ...keywords.map(keyword => new vscode.CompletionItem(keyword, vscode.CompletionItemKind.Keyword)),
+  ...builtinTypes.map(type => new vscode.CompletionItem(type, vscode.CompletionItemKind.Struct)),
+], /* isIncomplete: */ true);
+
 export function activate(context: vscode.ExtensionContext) {
 
+  // VSCode does not support having both its built-in suggestions _and_ a custom completion provider.
+  // But, without a proper LSP, we do want both!
+  // Registering the provider directly on "wit" would disable VSCode's built-in suggestions.
+  // The workaround is to register it for all languages (`*`) and then dynamically check the document type.
+  const provider = vscode.languages.registerCompletionItemProvider('*', {
+    provideCompletionItems(document: vscode.TextDocument, position: vscode.Position, token: vscode.CancellationToken, context: vscode.CompletionContext) {
+      if (document.languageId !== 'wit') {
+        return;
+      }
+
+      return staticCompletions;
+    }
+  });
+
+  context.subscriptions.push(provider);
 }
 
 export function deactivate() {