feat: Print AwaitBlock

src/node/block/await.ts

@@ -1,28 +1,140 @@
+/**
+ * Related to Svelte AST node {@link AwaitBlock}.
+ * @see {@link https://svelte.dev/docs/logic-blocks#await}
+ * @module
+ */
+
 import { print } from "esrap";
 
 import { print_fragment } from "#node/fragment";
 import { define_printer } from "#printer";
 import type { AwaitBlock } from "#types";
+import { insert } from "#util";
 
+/**
+ * Print Svelte AST node {@link AwaitBlock} as string.
+ * @see {@link https://svelte.dev/docs/logic-blocks#await}
+ *
+ * @example standard
+ * ```svelte
+ * {#await expression}...{:then name}...{:catch name}...{/await}
+ * ```
+ *
+ * @example without catch
+ * ```svelte
+ * {#if expression}...{:else if expression}...{/if}
+ * ```
+ *
+ * @example without pending body
+ * ```svelte
+ * {#await expression then name}...{/await}
+ * ```
+ *
+ * @example with catch body only
+ * ```svelte
+ * https://svelte.dev/docs/logic-blocks#await
+ * ```
+ */
 export const print_await_block = define_printer((node: AwaitBlock, options) => {
 	const { catch: catch_, error, expression, pending, then, value } = node;
-	return [
-		`{#await ${print(expression).code}}`,
-		pending ? print_fragment(pending, options) : "",
-		[
-			// then block
-			"{:then",
-			value ? ` ${print(value).code}` : "",
-			"}",
-			then ? print_fragment(then, options) : "",
-		].join(""),
-		[
-			// catch block
-			"{:catch",
-			error ? ` ${print(error).code}` : "",
-			"}",
-			catch_ ? print_fragment(catch_, options) : "",
-		].join(""),
+
+	return insert(
+		"{#await ",
+		print(expression).code,
+		insert(
+			then && !pending && insert(" then", value && insert(" ", print(value).code)),
+			catch_ && !pending && insert(" catch", error && insert(" ", print(error).code)),
+		),
+		"}",
+		pending && print_fragment(pending, options),
+		then &&
+			insert(
+				pending && insert("{:then", value && insert(" ", print(value).code), "}"),
+				print_fragment(then, options),
+			),
+		catch_ &&
+			insert(
+				pending && insert("{:catch", error && insert(" ", print(error).code), "}"),
+				print_fragment(catch_, options),
+			),
 		"{/await}",
-	].join("");
+	);
 });
+
+if (import.meta.vitest) {
+	const { describe, it } = import.meta.vitest;
+	const [{ parse_and_extract_svelte_node }, { DEFAULT_OPTIONS }] = await Promise.all([
+		import("#test/mod"),
+		import("#options"),
+	]);
+
+	describe("AwaitBlock", () => {
+		it("correctly prints standard example", ({ expect }) => {
+			const code = `
+				{#await promise}
+					<p>waiting for the promise to resolve...</p>
+				{:then value}
+					<p>The value is {value}</p>
+				{:catch error}
+					<p>Something went wrong: {error.message}</p>
+				{/await}
+			`;
+			const node = parse_and_extract_svelte_node<AwaitBlock>(code, "AwaitBlock");
+			expect(print_await_block(node, DEFAULT_OPTIONS)).toMatchInlineSnapshot(`
+				"{#await promise}
+					<p>waiting for the promise to resolve...</p>
+				{:then value}
+					<p>The value is {value}</p>
+				{:catch error}
+					<p>Something went wrong: {error.message}</p>
+				{/await}"
+			`);
+		});
+
+		it("correctly prints with omitted catch", ({ expect }) => {
+			const code = `
+				{#await promise}
+					<p>waiting for the promise to resolve...</p>
+				{:then value}
+					<p>The value is {value}</p>
+				{/await}
+			`;
+			const node = parse_and_extract_svelte_node<AwaitBlock>(code, "AwaitBlock");
+			expect(print_await_block(node, DEFAULT_OPTIONS)).toMatchInlineSnapshot(`
+				"{#await promise}
+					<p>waiting for the promise to resolve...</p>
+				{:then value}
+					<p>The value is {value}</p>
+				{/await}"
+			`);
+		});
+
+		it("correctly prints omitted initial block", ({ expect }) => {
+			const code = `
+				{#await promise then value}
+					<p>The value is {value}</p>
+				{/await}
+			`;
+			const node = parse_and_extract_svelte_node<AwaitBlock>(code, "AwaitBlock");
+			expect(print_await_block(node, DEFAULT_OPTIONS)).toMatchInlineSnapshot(`
+				"{#await promise then value}
+					<p>The value is {value}</p>
+				{/await}"
+			`);
+		});
+
+		it("correctly prints omitted then block", ({ expect }) => {
+			const code = `
+				{#await promise catch error}
+					<p>The error is {error}</p>
+				{/await}
+			`;
+			const node = parse_and_extract_svelte_node<AwaitBlock>(code, "AwaitBlock");
+			expect(print_await_block(node, DEFAULT_OPTIONS)).toMatchInlineSnapshot(`
+				"{#await promise catch error}
+					<p>The error is {error}</p>
+				{/await}"
+			`);
+		});
+	});
+}

src/node/block/if.ts

@@ -9,6 +9,7 @@ import { print } from "esrap";
 import { print_fragment } from "#node/fragment";
 import { define_printer } from "#printer";
 import type { Fragment, IfBlock } from "#types";
+import { insert } from "#util";
 
 const has_alternate_else_if = (node: Fragment): boolean => node.nodes.some((n) => n.type === "IfBlock");
 
@@ -45,37 +46,25 @@ export const print_if_block = define_printer((node: IfBlock, options) => {
 	const { alternate, consequent, elseif, test } = node;
 
 	if (elseif) {
-		return [
+		return insert(
 			"{:else if",
 			" ",
 			print(test).code,
 			"}",
 			print_fragment(consequent, options),
-			alternate
-				? [
-						//
-						!has_alternate_else_if(alternate) ? "{:else}" : "",
-						print_fragment(alternate, options),
-					].join("")
-				: "",
-		].join("");
+			alternate && insert(!has_alternate_else_if(alternate) && "{:else}", print_fragment(alternate, options)),
+		);
 	}
 
-	return [
+	return insert(
 		"{#if",
 		" ",
 		print(test).code,
 		"}",
 		print_fragment(consequent, options),
-		alternate
-			? [
-					//
-					!has_alternate_else_if(alternate) ? "{:else}" : "",
-					print_fragment(alternate, options),
-				].join("")
-			: "",
+		alternate && insert(!has_alternate_else_if(alternate) && "{:else}", print_fragment(alternate, options)),
 		"{/if}",
-	].join("");
+	);
 });
 
 if (import.meta.vitest) {

src/node/tag/expression.ts

@@ -7,6 +7,7 @@ import { print } from "esrap";
 
 import { define_printer } from "#printer";
 import type { ExpressionTag } from "#types";
+import { insert } from "#util";
 
 /**
  * Print Svelte AST node {@link ExpressionTag} as string.
@@ -18,12 +19,7 @@ import type { ExpressionTag } from "#types";
  */
 export const print_expression_tag = define_printer((node: ExpressionTag, _options) => {
 	const { expression } = node;
-	return [
-		//
-		"{",
-		print(expression).code,
-		"}",
-	].join("");
+	return insert("{", print(expression).code, "}");
 });
 
 if (import.meta.vitest) {

src/util.ts

@@ -1 +1,16 @@
 export const NEW_LINE = "\n";
+
+/**
+ * Filter out the falsy values and join the truthy (string) values together.
+ */
+export function insert(...values: (string | null | false)[]) {
+	let results = "";
+
+	for (const value of values) {
+		if (typeof value === "string") {
+			results += value;
+		}
+	}
+
+	return results;
+}