feat: wrap and rethrow swc errors

biome.json

@@ -19,7 +19,8 @@
 			"deps/**",
 			"lib/**",
 			"node_modules/**",
-			"test/snapshot/**"
+			"test/snapshot/**",
+			"test/fixtures/**"
 		]
 	}
 }

esbuild.config.mjs

@@ -27,6 +27,13 @@ await build({
 	plugins: [copyPlugin],
 });
 
+await build({
+	entryPoints: ["src/errors.ts"],
+	platform: "node",
+	target: "node22",
+	outfile: "dist/errors.js",
+});
+
 await build({
 	entryPoints: ["src/strip-loader.ts"],
 	bundle: false,

src/errors.ts

@@ -0,0 +1,24 @@
+type SwcError = {
+	code: "UnsupportedSyntax" | "InvalidSyntax";
+	message: string;
+};
+
+// Type guard to check if error is SwcError
+export function isSwcError(error: unknown): error is SwcError {
+	return (error as SwcError).code !== undefined;
+}
+
+// Since swc throw an object, we need to wrap it in a proper error
+export function wrapAndReThrowSwcError(error: SwcError): never {
+	switch (error.code) {
+		case "UnsupportedSyntax": {
+			const unsupportedSyntaxError = new Error(error.message);
+			unsupportedSyntaxError.name = "UnsupportedSyntaxError";
+			throw unsupportedSyntaxError;
+		}
+		case "InvalidSyntax":
+			throw new SyntaxError(error.message);
+		default:
+			throw error;
+	}
+}

src/strip-loader.ts

@@ -1,36 +1,42 @@
 import type { LoadFnOutput, LoadHookContext } from "node:module";
-import type { Options } from "../lib/wasm";
+import { isSwcError, wrapAndReThrowSwcError } from "./errors.js";
 import { transformSync } from "./index.js";
 
-type NextLoad = (
-	url: string,
-	context?: LoadHookContext,
-) => LoadFnOutput | Promise<LoadFnOutput>;
-
 export async function load(
 	url: string,
 	context: LoadHookContext,
-	nextLoad: NextLoad,
+	nextLoad: (
+		url: string,
+		context?: LoadHookContext,
+	) => LoadFnOutput | Promise<LoadFnOutput>,
 ) {
 	const { format } = context;
 	if (format.endsWith("-typescript")) {
 		// Use format 'module' so it returns the source as-is, without stripping the types.
 		// Format 'commonjs' would not return the source for historical reasons.
-		const { source } = await nextLoad(url, {
-			...context,
-			format: "module",
-		});
-		// biome-ignore lint/style/noNonNullAssertion: If module exists, it will have a source
-		const { code } = transformSync(source!.toString(), {
-			mode: "strip-only",
-		} as Options);
-		return {
-			format: format.replace("-typescript", ""),
-			// Source map is not necessary in strip-only mode. However, to map the source
-			// file in debuggers to the original TypeScript source, add a sourceURL magic
-			// comment to hint that it is a generated source.
-			source: `${code}\n\n//# sourceURL=${url}`,
-		};
+		try {
+			const { source } = await nextLoad(url, {
+				...context,
+				format: "module",
+			});
+			// biome-ignore lint/style/noNonNullAssertion: If module exists, it will have a source
+			const { code } = transformSync(source!.toString(), {
+				mode: "strip-only",
+			});
+			return {
+				format: format.replace("-typescript", ""),
+				// Source map is not necessary in strip-only mode. However, to map the source
+				// file in debuggers to the original TypeScript source, add a sourceURL magic
+				// comment to hint that it is a generated source.
+				source: `${code}\n\n//# sourceURL=${url}`,
+			};
+		} catch (error: unknown) {
+			if (isSwcError(error)) {
+				wrapAndReThrowSwcError(error);
+			}
+			// If the error is not an SwcError, rethrow it
+			throw error;
+		}
 	}
 	return nextLoad(url, context);
 }

src/transform-loader.ts

@@ -1,44 +1,51 @@
 import type { LoadFnOutput, LoadHookContext } from "node:module";
 import type { Options } from "../lib/wasm";
+import { isSwcError, wrapAndReThrowSwcError } from "./errors.js";
 import { transformSync } from "./index.js";
 
-type NextLoad = (
-	url: string,
-	context?: LoadHookContext,
-) => LoadFnOutput | Promise<LoadFnOutput>;
-
 export async function load(
 	url: string,
 	context: LoadHookContext,
-	nextLoad: NextLoad,
+	nextLoad: (
+		url: string,
+		context?: LoadHookContext,
+	) => LoadFnOutput | Promise<LoadFnOutput>,
 ) {
 	const { format } = context;
 	if (format.endsWith("-typescript")) {
-		// Use format 'module' so it returns the source as-is, without stripping the types.
-		// Format 'commonjs' would not return the source for historical reasons.
-		const { source } = await nextLoad(url, {
-			...context,
-			format: "module",
-		});
+		try {
+			// Use format 'module' so it returns the source as-is, without stripping the types.
+			// Format 'commonjs' would not return the source for historical reasons.
+			const { source } = await nextLoad(url, {
+				...context,
+				format: "module",
+			});
 
-		// biome-ignore lint/style/noNonNullAssertion: If module exists, it will have a source
-		const { code, map } = transformSync(source!.toString(), {
-			mode: "transform",
-			sourceMap: true,
-			filename: url,
-		} as Options);
+			// biome-ignore lint/style/noNonNullAssertion: If module exists, it will have a source
+			const { code, map } = transformSync(source!.toString(), {
+				mode: "transform",
+				sourceMap: true,
+				filename: url,
+			} as Options);
 
-		let output = code;
+			let output = code;
 
-		if (map) {
-			const base64SourceMap = Buffer.from(map).toString("base64");
-			output = `${code}\n\n//# sourceMappingURL=data:application/json;base64,${base64SourceMap}`;
-		}
+			if (map) {
+				const base64SourceMap = Buffer.from(map).toString("base64");
+				output = `${code}\n\n//# sourceMappingURL=data:application/json;base64,${base64SourceMap}`;
+			}
 
-		return {
-			format: format.replace("-typescript", ""),
-			source: `${output}\n\n//# sourceURL=${url}`,
-		};
+			return {
+				format: format.replace("-typescript", ""),
+				source: `${output}\n\n//# sourceURL=${url}`,
+			};
+		} catch (error) {
+			if (isSwcError(error)) {
+				wrapAndReThrowSwcError(error);
+			}
+			// If the error is not an SwcError, rethrow it
+			throw error;
+		}
 	}
 	return nextLoad(url, context);
 }

test/fixtures/invalid-syntax.ts

@@ -0,0 +1,3 @@
+function foo(){
+    await Promise.resolve();
+}

test/loader.test.js

@@ -24,6 +24,7 @@ test("should not work with enums", async () => {
 	]);
 
 	strictEqual(result.stdout, "");
+	match(result.stderr, /UnsupportedSyntaxError/);
 	match(result.stderr, /TypeScript enum is not supported in strip-only mode/);
 	strictEqual(result.code, 1);
 });
@@ -93,3 +94,17 @@ test("should call nextLoader for non-typescript files for transform", async () =
 	match(result.stdout, /Hello, JavaScript!/);
 	strictEqual(result.code, 0);
 });
+
+test("should throw syntax error for invalid typescript", async () => {
+	const result = await spawnPromisified(process.execPath, [
+		"--experimental-strip-types",
+		"--no-warnings",
+		"--import=./dist/register-strip.mjs",
+		fixturesPath("invalid-syntax.ts"),
+	]);
+
+	strictEqual(result.stdout, "");
+	match(result.stderr, /SyntaxError/);
+	match(result.stderr, /await isn't allowed in non-async function/);
+	strictEqual(result.code, 1);
+});