From 0b2b77cb1912845e7d2c2e5837d29d1f03dd5858 Mon Sep 17 00:00:00 2001
From: Milan Hauth <milahu@gmail.com>
Date: Sun, 3 Jan 2021 19:45:02 +0100
Subject: [PATCH 1/7] add: parse attached sourcemap from preprocessor

---
 src/compiler/preprocess/index.ts              |  9 +++-
 src/compiler/utils/string_with_sourcemap.ts   | 25 +++++++++++
 test/sourcemaps/index.ts                      |  9 ++--
 .../samples/attached-sourcemap/_config.js     | 37 +++++++++++++++
 .../samples/attached-sourcemap/input.svelte   | 11 +++++
 .../samples/attached-sourcemap/test.js        | 45 +++++++++++++++++++
 6 files changed, 132 insertions(+), 4 deletions(-)
 create mode 100644 test/sourcemaps/samples/attached-sourcemap/_config.js
 create mode 100644 test/sourcemaps/samples/attached-sourcemap/input.svelte
 create mode 100644 test/sourcemaps/samples/attached-sourcemap/test.js

diff --git a/src/compiler/preprocess/index.ts b/src/compiler/preprocess/index.ts
index 264fbbdbcd42..660a327e2d3b 100644
--- a/src/compiler/preprocess/index.ts
+++ b/src/compiler/preprocess/index.ts
@@ -1,7 +1,12 @@
 import { RawSourceMap, DecodedSourceMap } from '@ampproject/remapping/dist/types/types';
 import { decode as decode_mappings } from 'sourcemap-codec';
 import { getLocator } from 'locate-character';
-import { StringWithSourcemap, sourcemap_add_offset, combine_sourcemaps } from '../utils/string_with_sourcemap';
+import {
+	StringWithSourcemap,
+	sourcemap_add_offset,
+	combine_sourcemaps,
+	parse_attached_sourcemap
+} from '../utils/string_with_sourcemap';
 
 export interface Processed {
 	code: string;
@@ -179,6 +184,8 @@ function get_replacement(
 	const suffix_with_map = StringWithSourcemap.from_source(
 		file_basename, suffix, get_location(offset + prefix.length + original.length));
 
+	parse_attached_sourcemap(processed);
+
 	// Convert the preprocessed code and its sourcemap to a StringWithSourcemap
 	let decoded_map: DecodedSourceMap;
 	if (processed.map) {
diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index 1766a0db069a..4a442b964a94 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/src/compiler/utils/string_with_sourcemap.ts
@@ -1,6 +1,7 @@
 import { DecodedSourceMap, RawSourceMap, SourceMapLoader } from '@ampproject/remapping/dist/types/types';
 import remapping from '@ampproject/remapping';
 import { SourceMap } from 'magic-string';
+import { Processed } from '../preprocess';
 
 type SourceLocation = {
 	line: number;
@@ -255,6 +256,7 @@ export function combine_sourcemaps(
 
 // browser vs node.js
 const b64enc = typeof btoa == 'function' ? btoa : b => Buffer.from(b).toString('base64');
+const b64dec = typeof atob == 'function' ? atob : a => Buffer.from(a, 'base64').toString();
 
 export function apply_preprocessor_sourcemap(filename: string, svelte_map: SourceMap, preprocessor_map_input: string | DecodedSourceMap | RawSourceMap): SourceMap {
 	if (!svelte_map || !preprocessor_map_input) return svelte_map;
@@ -288,3 +290,26 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 
 	return result_map as SourceMap;
 }
+
+// find attached sourcemap in processed.code
+// TODO? handle multiple attached maps, combine with processed.map
+export function parse_attached_sourcemap(processed: Processed): void {
+	const magic_prefix = '\n/*# 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
+	}
+	if (processed.map) {
+		throw 'not implemented. '+
+			'found sourcemap in both processed.code and processed.map. '+
+			'please pass only one sourcemap.\n'+
+			'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.map = b64dec(b64map);
+}
diff --git a/test/sourcemaps/index.ts b/test/sourcemaps/index.ts
index 4122c3a41969..f00c2ced338b 100644
--- a/test/sourcemaps/index.ts
+++ b/test/sourcemaps/index.ts
@@ -31,7 +31,8 @@ describe('sourcemaps', () => {
 			const inputCode = fs.readFileSync(inputFile, 'utf-8');
 			const input = {
 				code: inputCode,
-				locate: getLocator(inputCode)
+				locate: getLocator(inputCode),
+				locate_1: getLocator(inputCode, { offsetLine: 1 })
 			};
 
 			const preprocessed = await svelte.preprocess(
@@ -86,12 +87,14 @@ describe('sourcemaps', () => {
 
 			assert.deepEqual(
 				js.map.sources.slice().sort(),
-				(config.js_map_sources || ['input.svelte']).sort()
+				(config.js_map_sources || ['input.svelte']).sort(),
+				'js.map.sources is wrong'
 			);
 			if (css.map) {
 				assert.deepEqual(
 					css.map.sources.slice().sort(),
-					(config.css_map_sources || ['input.svelte']).sort()
+					(config.css_map_sources || ['input.svelte']).sort(),
+					'css.map.sources is wrong'
 				);
 			}
 
diff --git a/test/sourcemaps/samples/attached-sourcemap/_config.js b/test/sourcemaps/samples/attached-sourcemap/_config.js
new file mode 100644
index 000000000000..588ab7515cfa
--- /dev/null
+++ b/test/sourcemaps/samples/attached-sourcemap/_config.js
@@ -0,0 +1,37 @@
+import MagicString from 'magic-string';
+
+let indent_size = 4;
+function get_processor(search, replace) {
+	return ({ content, filename }) => {
+		let code = content.slice();
+		const ms = new MagicString(code);
+
+		const idx = ms.original.indexOf(search);
+		if (idx == -1) throw new Error('search not found in src');
+		ms.overwrite(idx, idx + search.length, replace, { storeName: true });
+
+		// change line + column
+		const indent = Array.from({ length: indent_size }).join(' ');
+		ms.prependLeft(idx, '\n'+indent);
+
+		const map_opts = { source: filename, hires: true, includeContent: false };
+		const map = ms.generateMap(map_opts);
+		const attach_line = `\n/*# sourceMappingURL=${map.toUrl()} */`;
+		code = ms.toString() + attach_line;
+
+		indent_size += 2;
+		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') },
+
+		{ style: get_processor('.replace_me_style', '.done_replace_style_1') },
+		{ style: get_processor('.done_replace_style_1', '.done_replace_style_2') }
+
+	]
+};
diff --git a/test/sourcemaps/samples/attached-sourcemap/input.svelte b/test/sourcemaps/samples/attached-sourcemap/input.svelte
new file mode 100644
index 000000000000..21a47a72a9c9
--- /dev/null
+++ b/test/sourcemaps/samples/attached-sourcemap/input.svelte
@@ -0,0 +1,11 @@
+<style>
+	.replace_me_style {
+		color: red;
+	}
+</style>
+<script>
+	let
+		replace_me_script = 'hello'
+	;
+</script>
+<h1 class="done_replace_style_2">{done_replace_script_2}</h1>
diff --git a/test/sourcemaps/samples/attached-sourcemap/test.js b/test/sourcemaps/samples/attached-sourcemap/test.js
new file mode 100644
index 000000000000..fde219080823
--- /dev/null
+++ b/test/sourcemaps/samples/attached-sourcemap/test.js
@@ -0,0 +1,45 @@
+import * as assert from 'assert';
+
+const get_line_column = obj => ({ line: obj.line, column: obj.column });
+
+export function test({ input, css, js }) {
+
+	let out_obj, loc_output, actual, loc_input, expected;
+
+	out_obj = js;
+	// we need the seconds occurence in output.js
+	loc_output = out_obj.locate_1('done_replace_script_2');
+	loc_output = out_obj.locate_1('done_replace_script_2', loc_output.character + 1);
+	actual = out_obj.mapConsumer.originalPositionFor(loc_output);
+	loc_input = input.locate_1('replace_me_script');
+	expected = {
+		source: 'input.svelte',
+		name: 'replace_me_script',
+		...get_line_column(loc_input)
+	};
+	assert.deepEqual(actual, expected);
+
+	out_obj = css;
+	loc_output = out_obj.locate_1('.done_replace_style_2');
+	actual = out_obj.mapConsumer.originalPositionFor(loc_output);
+	// first occurence in input.svelte
+	loc_input = input.locate_1('.replace_me_style');
+	expected = {
+		source: 'input.svelte',
+		name: '.replace_me_style',
+		...get_line_column(loc_input)
+	};
+	assert.deepEqual(actual, expected);
+
+	assert.equal(
+		js.code.indexOf('\n/*# sourceMappingURL=data:application/json;base64,'),
+		-1,
+		'magic-comment attachments were NOT removed'
+	);
+
+	assert.equal(
+		css.code.indexOf('\n/*# sourceMappingURL=data:application/json;base64,'),
+		-1,
+		'magic-comment attachments were NOT removed'
+	);
+}

From 9d17d7872979b9dc3be030d46c5ba020a0503b71 Mon Sep 17 00:00:00 2001
From: Milan Hauth <milahu@gmail.com>
Date: Mon, 4 Jan 2021 20:01:50 +0100
Subject: [PATCH 2/7] fix

---
 src/compiler/utils/string_with_sourcemap.ts        | 3 +--
 test/sourcemaps/samples/attached-sourcemap/test.js | 4 ++--
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index 4a442b964a94..dc182a6321b2 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/src/compiler/utils/string_with_sourcemap.ts
@@ -291,8 +291,7 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 	return result_map as SourceMap;
 }
 
-// find attached sourcemap in processed.code
-// TODO? handle multiple attached maps, combine with processed.map
+// parse attached sourcemap in processed.code
 export function parse_attached_sourcemap(processed: Processed): void {
 	const magic_prefix = '\n/*# sourceMappingURL=data:application/json;';
 	const cut_index = processed.code.lastIndexOf('\n');
diff --git a/test/sourcemaps/samples/attached-sourcemap/test.js b/test/sourcemaps/samples/attached-sourcemap/test.js
index fde219080823..c5b4d7989dce 100644
--- a/test/sourcemaps/samples/attached-sourcemap/test.js
+++ b/test/sourcemaps/samples/attached-sourcemap/test.js
@@ -7,7 +7,8 @@ export function test({ input, css, js }) {
 	let out_obj, loc_output, actual, loc_input, expected;
 
 	out_obj = js;
-	// we need the seconds occurence in output.js
+	// we need the second occurence of 'done_replace_script_2' in output.js
+	// the first occurence is mapped back to markup '{done_replace_script_2}'
 	loc_output = out_obj.locate_1('done_replace_script_2');
 	loc_output = out_obj.locate_1('done_replace_script_2', loc_output.character + 1);
 	actual = out_obj.mapConsumer.originalPositionFor(loc_output);
@@ -22,7 +23,6 @@ export function test({ input, css, js }) {
 	out_obj = css;
 	loc_output = out_obj.locate_1('.done_replace_style_2');
 	actual = out_obj.mapConsumer.originalPositionFor(loc_output);
-	// first occurence in input.svelte
 	loc_input = input.locate_1('.replace_me_style');
 	expected = {
 		source: 'input.svelte',

From a5ae6b3b7e57fc68ebb408ec0cde105436685051 Mon Sep 17 00:00:00 2001
From: Milan Hauth <milahu@gmail.com>
Date: Mon, 4 Jan 2021 22:13:55 +0100
Subject: [PATCH 3/7] attached sourcemap: support single line comments in
 script

---
 src/compiler/preprocess/index.ts              |  7 ++-
 src/compiler/utils/string_with_sourcemap.ts   | 18 +++---
 test/sourcemaps/index.ts                      |  2 +-
 .../samples/attached-sourcemap/_config.js     | 55 +++++++++++--------
 4 files changed, 45 insertions(+), 37 deletions(-)

diff --git a/src/compiler/preprocess/index.ts b/src/compiler/preprocess/index.ts
index 660a327e2d3b..e0847898d546 100644
--- a/src/compiler/preprocess/index.ts
+++ b/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;
diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index dc182a6321b2..b0507aa2f847 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/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);
 }
diff --git a/test/sourcemaps/index.ts b/test/sourcemaps/index.ts
index f00c2ced338b..903629c06b1b 100644
--- a/test/sourcemaps/index.ts
+++ b/test/sourcemaps/index.ts
@@ -42,7 +42,7 @@ describe('sourcemaps', () => {
 					filename: 'input.svelte'
 				}
 			);
-	
+
 			const { js, css } = svelte.compile(
 				preprocessed.code, {
 				filename: 'input.svelte',
diff --git a/test/sourcemaps/samples/attached-sourcemap/_config.js b/test/sourcemaps/samples/attached-sourcemap/_config.js
index 588ab7515cfa..6d9786f6b068 100644
--- a/test/sourcemaps/samples/attached-sourcemap/_config.js
+++ b/test/sourcemaps/samples/attached-sourcemap/_config.js
@@ -1,37 +1,44 @@
 import MagicString from 'magic-string';
 
 let indent_size = 4;
-function get_processor(search, replace) {
-	return ({ content, filename }) => {
-		let code = content.slice();
-		const ms = new MagicString(code);
-
-		const idx = ms.original.indexOf(search);
-		if (idx == -1) throw new Error('search not found in src');
-		ms.overwrite(idx, idx + search.length, replace, { storeName: true });
-
-		// change line + column
-		const indent = Array.from({ length: indent_size }).join(' ');
-		ms.prependLeft(idx, '\n'+indent);
-
-		const map_opts = { source: filename, hires: true, includeContent: false };
-		const map = ms.generateMap(map_opts);
-		const attach_line = `\n/*# sourceMappingURL=${map.toUrl()} */`;
-		code = ms.toString() + attach_line;
-
-		indent_size += 2;
-		return { code };
+let comment_multi = true;
+function get_processor(tag_name, search, replace) {
+	return {
+		[tag_name]: ({ content, filename }) => {
+			let code = content.slice();
+			const ms = new MagicString(code);
+
+			const idx = ms.original.indexOf(search);
+			if (idx == -1) throw new Error('search not found in src');
+			ms.overwrite(idx, idx + search.length, replace, { storeName: true });
+
+			// change line + column
+			const indent = Array.from({ length: indent_size }).join(' ');
+			ms.prependLeft(idx, '\n'+indent);
+
+			const map_opts = { source: filename, hires: true, includeContent: false };
+			const map = ms.generateMap(map_opts);
+			const attach_line = (tag_name == 'style' || comment_multi)
+				? `\n/*# sourceMappingURL=${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')
 
 	]
 };

From dcaeb768e4f996c7267404cceab760252bc35ae8 Mon Sep 17 00:00:00 2001
From: Milan Hauth <milahu@gmail.com>
Date: Wed, 6 Jan 2021 20:02:05 +0100
Subject: [PATCH 4/7] attached sourcemap: use regex

---
 src/compiler/utils/string_with_sourcemap.ts | 37 +++++++++++----------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index b0507aa2f847..d87868f939ec 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/src/compiler/utils/string_with_sourcemap.ts
@@ -293,22 +293,23 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 
 // parse attached sourcemap in processed.code
 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);
-	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. '+
-			'please pass only one sourcemap.\n'+
-			'processed.code:\n'+
-			processed.code.slice(0, 100)+' [....]'; // help to find preprocessor
-	}
-	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);
+	const r_in = '[#@]\\s*sourceMappingURL\\s*=\\s*data:' + 
+		'(?:application|text)/json;(?:charset[:=]\\S+?;)?base64,(\\S*)';
+	const regex = (tag_name == 'script')
+		? new RegExp('(?://'+r_in+')|(?:/\\*'+r_in+'\\s*\\*/)$')
+		: new RegExp('/\\*'+r_in+'\\s*\\*/$');
+	processed.code = processed.code.replace(regex, (_, match1, match2) => {
+		if (processed.map) {
+			throw 'not implemented. '+
+				'found sourcemap in both processed.code and processed.map. '+
+				'please pass only one sourcemap.\n'+
+				'processed.code:\n'+
+				processed.code.slice(0, 100)+' [....]'; // help to find preprocessor
+		}
+		const map64 = (tag_name == 'script')
+			? (match1 || match2)
+			: match1;
+		processed.map = b64dec(map64);
+		return ''; // remove from processed.code
+	});
 }

From 4a1450b46f1e8e74aad5dca0122c1a50a2db11a7 Mon Sep 17 00:00:00 2001
From: milahu <milahu@gmail.com>
Date: Mon, 18 Jan 2021 20:10:32 +0100
Subject: [PATCH 5/7] remove attached sourcemap path

---
 src/compiler/utils/string_with_sourcemap.ts | 36 ++++++++++++++-------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index d87868f939ec..52c69b7b1082 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/src/compiler/utils/string_with_sourcemap.ts
@@ -293,23 +293,35 @@ export function apply_preprocessor_sourcemap(filename: string, svelte_map: Sourc
 
 // parse attached sourcemap in processed.code
 export function parse_attached_sourcemap(processed: Processed, tag_name: 'script' | 'style'): void {
-	const r_in = '[#@]\\s*sourceMappingURL\\s*=\\s*data:' + 
-		'(?:application|text)/json;(?:charset[:=]\\S+?;)?base64,(\\S*)';
+	const r_in = '[#@]\\s*sourceMappingURL\\s*=\\s*(\\S*)';
 	const regex = (tag_name == 'script')
 		? new RegExp('(?://'+r_in+')|(?:/\\*'+r_in+'\\s*\\*/)$')
 		: new RegExp('/\\*'+r_in+'\\s*\\*/$');
+	function throw_error(message) {
+		throw 'error: ' + message + '\nprocessed.code:\n' +
+			(processed.code.length < 100 ? processed.code : processed.code.slice(0, 100)+' [...]'); // help to find preprocessor
+	}
 	processed.code = processed.code.replace(regex, (_, match1, match2) => {
-		if (processed.map) {
-			throw 'not implemented. '+
-				'found sourcemap in both processed.code and processed.map. '+
-				'please pass only one sourcemap.\n'+
-				'processed.code:\n'+
-				processed.code.slice(0, 100)+' [....]'; // help to find preprocessor
+		const map_url = (tag_name == 'script') ? (match1 || match2) : match1;
+		const map_data = (map_url.match(/data:(?:application|text)\/json;(?:charset[:=]\S+?;)?base64,(\S*)/) || [])[1];
+		if (map_data) {
+			// sourceMappingURL is data URL
+			if (processed.map) {
+				throw_error('not implemented. '+
+					'found sourcemap in both processed.code and processed.map. '+
+					'please pass only one sourcemap.');
+			}
+			processed.map = b64dec(map_data); // use attached sourcemap
+			return ''; // remove from processed.code
+		}
+		// sourceMappingURL is file path or URL
+		if (!processed.map) {
+			// TODO show warning? silently ignore?
+			throw_error('value error. processed.map is empty, '+
+				'but processed.code has attached sourcemap file '+map_url+'. '+
+				'please make your preprocessor return a sourcemap.');
 		}
-		const map64 = (tag_name == 'script')
-			? (match1 || match2)
-			: match1;
-		processed.map = b64dec(map64);
+		// ignore sourcemap file path
 		return ''; // remove from processed.code
 	});
 }

From a29e2d0394f58c701a0d4e348af8cbb715e41d73 Mon Sep 17 00:00:00 2001
From: milahu <milahu@gmail.com>
Date: Tue, 19 Jan 2021 09:32:52 +0100
Subject: [PATCH 6/7] fix: warnings, lint

---
 src/compiler/utils/string_with_sourcemap.ts | 22 ++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index 52c69b7b1082..6cf14db5fc9f 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/src/compiler/utils/string_with_sourcemap.ts
@@ -297,9 +297,10 @@ export function parse_attached_sourcemap(processed: Processed, tag_name: 'script
 	const regex = (tag_name == 'script')
 		? new RegExp('(?://'+r_in+')|(?:/\\*'+r_in+'\\s*\\*/)$')
 		: new RegExp('/\\*'+r_in+'\\s*\\*/$');
-	function throw_error(message) {
-		throw 'error: ' + message + '\nprocessed.code:\n' +
-			(processed.code.length < 100 ? processed.code : processed.code.slice(0, 100)+' [...]'); // help to find preprocessor
+	function log_warning(message) {
+		// code_start: help to find preprocessor
+		const code_start = processed.code.length < 100 ? processed.code : (processed.code.slice(0, 100) + ' [...]');
+		console.warn(`warning: ${message}. processed.code = ${JSON.stringify(code_start)}`);
 	}
 	processed.code = processed.code.replace(regex, (_, match1, match2) => {
 		const map_url = (tag_name == 'script') ? (match1 || match2) : match1;
@@ -307,21 +308,20 @@ export function parse_attached_sourcemap(processed: Processed, tag_name: 'script
 		if (map_data) {
 			// sourceMappingURL is data URL
 			if (processed.map) {
-				throw_error('not implemented. '+
-					'found sourcemap in both processed.code and processed.map. '+
-					'please pass only one sourcemap.');
+				log_warning('not implemented. ' +
+					'found sourcemap in both processed.code and processed.map. ' +
+					'please make your preprocessor return only one sourcemap.');
 			}
 			processed.map = b64dec(map_data); // use attached sourcemap
 			return ''; // remove from processed.code
 		}
-		// sourceMappingURL is file path or URL
+		// sourceMappingURL is path or URL
 		if (!processed.map) {
-			// TODO show warning? silently ignore?
-			throw_error('value error. processed.map is empty, '+
-				'but processed.code has attached sourcemap file '+map_url+'. '+
+			log_warning('value error. processed.map is empty, ' +
+				`but processed.code has attached sourcemap path ${JSON.stringify(map_url)}. ` +
 				'please make your preprocessor return a sourcemap.');
 		}
-		// ignore sourcemap file path
+		// ignore sourcemap path
 		return ''; // remove from processed.code
 	});
 }

From 2fe7c0e9a9d5b79b6c87f754899f8643f22d94f3 Mon Sep 17 00:00:00 2001
From: milahu <milahu@gmail.com>
Date: Tue, 19 Jan 2021 18:33:40 +0100
Subject: [PATCH 7/7] fix warning, in doubt ignore attached sourcemap

---
 src/compiler/utils/string_with_sourcemap.ts | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/compiler/utils/string_with_sourcemap.ts b/src/compiler/utils/string_with_sourcemap.ts
index 6cf14db5fc9f..3002e10d849d 100644
--- a/src/compiler/utils/string_with_sourcemap.ts
+++ b/src/compiler/utils/string_with_sourcemap.ts
@@ -308,18 +308,19 @@ export function parse_attached_sourcemap(processed: Processed, tag_name: 'script
 		if (map_data) {
 			// sourceMappingURL is data URL
 			if (processed.map) {
-				log_warning('not implemented. ' +
-					'found sourcemap in both processed.code and processed.map. ' +
-					'please make your preprocessor return only one sourcemap.');
+				log_warning('Not implemented. ' +
+					'Found sourcemap in both processed.code and processed.map. ' +
+					'Please update your preprocessor to return only one sourcemap.');
+				// ignore attached sourcemap
+				return '';
 			}
 			processed.map = b64dec(map_data); // use attached sourcemap
 			return ''; // remove from processed.code
 		}
 		// sourceMappingURL is path or URL
 		if (!processed.map) {
-			log_warning('value error. processed.map is empty, ' +
-				`but processed.code has attached sourcemap path ${JSON.stringify(map_url)}. ` +
-				'please make your preprocessor return a sourcemap.');
+			log_warning(`Found sourcemap path ${JSON.stringify(map_url)} in processed.code, but no sourcemap data. ` +
+				'Please update your preprocessor to return sourcemap data directly.');
 		}
 		// ignore sourcemap path
 		return ''; // remove from processed.code