attached sourcemap: support single line comments in script

src/compiler/preprocess/index.ts

@@ -175,7 +175,8 @@ function get_replacement(
 	original: string,
 	processed: Processed,
 	prefix: string,
-	suffix: string
+	suffix: string,
+	tag_name: 'script' | 'style'
 ): StringWithSourcemap {
 
 	// Convert the unchanged prefix and suffix to StringWithSourcemap
@@ -184,7 +185,7 @@ function get_replacement(
 	const suffix_with_map = StringWithSourcemap.from_source(
 		file_basename, suffix, get_location(offset + prefix.length + original.length));
 
-	parse_attached_sourcemap(processed);
+	parse_attached_sourcemap(processed, tag_name);
 
 	// Convert the preprocessed code and its sourcemap to a StringWithSourcemap
 	let decoded_map: DecodedSourceMap;
@@ -289,7 +290,7 @@ export default async function preprocess(
 				if (!processed || !processed.map && processed.code === content) {
 					return no_change();
 				}
-				return get_replacement(file_basename, offset, get_location, content, processed, `<${tag_name}${attributes}>`, `</${tag_name}>`);
+				return get_replacement(file_basename, offset, get_location, content, processed, `<${tag_name}${attributes}>`, `</${tag_name}>`, tag_name);
 			}
 		);
 		source = res.string;

src/compiler/utils/string_with_sourcemap.ts

@@ -292,13 +292,14 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 }
 
 // parse attached sourcemap in processed.code
-export function parse_attached_sourcemap(processed: Processed): void {
-	const magic_prefix = '\n/*# sourceMappingURL=data:application/json;';
+export function parse_attached_sourcemap(processed: Processed, tag_name: 'script' | 'style'): void {
+	const magic_prefix = '# sourceMappingURL=data:application/json;';
 	const cut_index = processed.code.lastIndexOf('\n');
 	const last_line = processed.code.slice(cut_index);
-	if (magic_prefix != last_line.slice(0, magic_prefix.length)) {
-		return; // attachment not found
-	}
+	const line_start = last_line.slice(1, 3); // last_line[0] == '\n'
+	if ((line_start != '/*' && (tag_name == 'script' && line_start != '//')) ||
+		magic_prefix != last_line.slice(3, 3 + magic_prefix.length)
+	) return; // attachment not found
 	if (processed.map) {
 		throw 'not implemented. '+
 			'found sourcemap in both processed.code and processed.map. '+
@@ -306,9 +307,8 @@ export function parse_attached_sourcemap(processed: Processed): void {
 			'processed.code:\n'+
 			processed.code.slice(0, 100)+' [....]'; // help to find preprocessor
 	}
-	// remove last line
-	processed.code = processed.code.slice(0, cut_index);
-	// slice to -2 --> remove trailing '*/'
-	const b64map = last_line.slice(last_line.indexOf('base64,')+7, -2).trim();
+	processed.code = processed.code.slice(0, cut_index); // remove last line
+	const slice_to = (line_start == '/*') ? -2 : undefined;
+	const b64map = last_line.slice(last_line.indexOf('base64,')+7, slice_to).trim();
 	processed.map = b64dec(b64map);
 }

test/sourcemaps/samples/attached-sourcemap/_config.js

@@ -1,8 +1,10 @@
 import MagicString from 'magic-string';
 
 let indent_size = 4;
-function get_processor(search, replace) {
-	return ({ content, filename }) => {
+let comment_multi = true;
+function get_processor(tag_name, search, replace) {
+	return {
+		[tag_name]: ({ content, filename }) => {
 			let code = content.slice();
 			const ms = new MagicString(code);
 
@@ -16,22 +18,27 @@ function get_processor(search, replace) {
 
 			const map_opts = { source: filename, hires: true, includeContent: false };
 			const map = ms.generateMap(map_opts);
-		const attach_line = `\n/*# sourceMappingURL=${map.toUrl()} */`;
+			const attach_line = (tag_name == 'style' || comment_multi)
+				? `\n/*# sourceMappingURL=${map.toUrl()} */`
+				: `\n//# sourceMappingURL=${map.toUrl()}` // only in script
+			;
 			code = ms.toString() + attach_line;
 
 			indent_size += 2;
+			if (tag_name == 'script') comment_multi = !comment_multi;
 			return { code };
+		}
 	};
 }
 
 export default {
 	preprocess: [
 
-		{ script: get_processor('replace_me_script', 'done_replace_script_1') },
-		{ script: get_processor('done_replace_script_1', 'done_replace_script_2') },
+		get_processor('script', 'replace_me_script', 'done_replace_script_1'),
+		get_processor('script', 'done_replace_script_1', 'done_replace_script_2'),
 
-		{ style: get_processor('.replace_me_style', '.done_replace_style_1') },
-		{ style: get_processor('.done_replace_style_1', '.done_replace_style_2') }
+		get_processor('style', '.replace_me_style', '.done_replace_style_1'),
+		get_processor('style', '.done_replace_style_1', '.done_replace_style_2')
 
 	]
 };