Improve promised-handlebars types

Change-type: patch

lib/partials.ts

@@ -167,8 +167,8 @@ hb.registerHelper('import', async (options) => {
 			const safeContent = new hb.SafeString(
 				partialContent.slice(0, partialContent.length - 1),
 			);
-			const builtContent = await Promise.resolve(
-				hb.compile(safeContent.toString())(options.data.root),
+			const builtContent = await hb.compile(safeContent.toString())(
+				options.data.root,
 			);
 			return new hb.SafeString(builtContent);
 		} catch (err) {
@@ -248,7 +248,5 @@ export const buildTemplate = async (
 		context.toJSON().children,
 	);
 
-	return stripExtraBlankLines(
-		await Promise.resolve(hb.compile(template)(data)),
-	);
+	return stripExtraBlankLines(await hb.compile(template)(data));
 };

typings/promised-handlebars.d.ts

@@ -1,6 +1,29 @@
 declare module 'promised-handlebars' {
-	import type Handlebars from 'handlebars';
+	import type HandlebarsNS from 'handlebars';
 
-	const fn: (hb: typeof Handlebars) => typeof Handlebars;
+	// Extend the Handlebars type to include an async `compile` method
+	type Handlebars = typeof HandlebarsNS;
+
+	// Convert the template delegate to async
+	// Note: this was tested with handlebars 4.7.8
+	type HandlebarsTemplateDelegate<T> = Handlebars.TemplateDelegate<T>;
+	type HandlebarsTemplateDelegateArgs<T> = Parameters<
+		HandlebarsTemplateDelegate<T>
+	>;
+	type HandlebarsTemplateDelegateReturn<T> = ReturnType<
+		HandlebarsTemplateDelegate<T>
+	>;
+	type HandlebarsTemplateDelegateAsync<T> = (
+		...args: HandlebarsTemplateDelegateArgs<T>
+	) => Promise<HandlebarsTemplateDelegateReturn<T>>;
+
+	// Create a new Handlebars interface with an updated compile function
+	type CompileArgs = Parameters<Handlebars['compile']>;
+	interface HandlebarsAsync extends Handlebars {
+		compile: <T>(...args: CompileArgs) => HandlebarsTemplateDelegateAsync<T>;
+	}
+
+	// Define the function exported by the module
+	const fn: (hb: Handlebars) => HandlebarsAsync;
 	export = fn;
 }