chore: source maps for preprocessors + tests (#10459)

Add source map merging for preprocessors and get tests passing.

- fixed some issues around the `sources` array where they weren't calculated relative to the input correctly
- adjusted some CSS tests because due to our own CSS parser the AST is less granular, so there are less mappings now. Don't think this is a problem, but worth thinking about
- removed enableSourcemap but only log a warning, the reason this was introduced was to mitigate a bug in Vite which occured when having the source map inlined into the SSR'd output. Since SSR doesn't contain inlined CSS anymore (and if it did, we would omit the source map) the reason for which it was introduced no longer exists
- files without js mapping in it have no source mappings yet (originally added in Svelte 4 for #6092)

.changeset/silly-laws-happen.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: add proper source map support

packages/svelte/src/compiler/css/Stylesheet.js

@@ -2,9 +2,8 @@ import MagicString from 'magic-string';
 import { walk } from 'zimmerframe';
 import { ComplexSelector } from './Selector.js';
 import { hash } from './utils.js';
-// import compiler_warnings from '../compiler_warnings.js';
-// import { extract_ignores_above_position } from '../utils/extract_svelte_ignore.js';
 import { create_attribute } from '../phases/nodes.js'; // TODO move this
+import { merge_with_preprocessor_map } from '../utils/mapped_code.js';
 
 const regex_css_browser_prefix = /^-((webkit)|(moz)|(o)|(ms))-/;
 const regex_name_boundary = /^[\s,;}]$/;
@@ -337,7 +336,7 @@ export class Stylesheet {
 	/** @type {import('#compiler').Style | null} */
 	ast;
 
-	/** @type {string} */
+	/** @type {string} Path of Svelte file the CSS is in */
 	filename;
 
 	/** @type {boolean} */
@@ -471,20 +470,23 @@ export class Stylesheet {
 	}
 
 	/**
-	 * @param {string} file
 	 * @param {string} source
-	 * @param {boolean} dev
+	 * @param {import('#compiler').ValidatedCompileOptions} options
 	 */
-	render(file, source, dev) {
+	render(source, options) {
 		// TODO neaten this up
 		if (!this.ast) throw new Error('Unexpected error');
 
 		const code = new MagicString(source);
 
+		// Generate source mappings for the style sheet nodes we have.
+		// Note that resolution is a bit more coarse than in Svelte 4 because
+		// our own CSS AST is not as detailed with regards to the node values.
 		walk(/** @type {import('#compiler').Css.Node} */ (this.ast), null, {
-			_: (node) => {
+			_: (node, { next }) => {
 				code.addSourcemapLocation(node.start);
 				code.addSourcemapLocation(node.end);
+				next();
 			}
 		});
 
@@ -495,19 +497,27 @@ export class Stylesheet {
 		code.remove(0, this.ast.content.start);
 
 		for (const child of this.children) {
-			child.prune(code, dev);
+			child.prune(code, options.dev);
 		}
 
 		code.remove(/** @type {number} */ (this.ast.content.end), source.length);
 
-		return {
+		const css = {
 			code: code.toString(),
 			map: code.generateMap({
+				// include source content; makes it easier/more robust looking up the source map code
 				includeContent: true,
+				// generateMap takes care of calculating source relative to file
 				source: this.filename,
-				file
+				file: options.cssOutputFilename || this.filename
 			})
 		};
+		merge_with_preprocessor_map(css, options, css.map.sources[0]);
+		if (options.dev && options.css === 'injected' && css.code) {
+			css.code += `\n/*# sourceMappingURL=${css.map.toUrl()} */`;
+		}
+
+		return css;
 	}
 
 	/** @param {import('../phases/types.js').ComponentAnalysis} analysis */

packages/svelte/src/compiler/phases/1-parse/index.js

@@ -7,6 +7,7 @@ import full_char_code_at from './utils/full_char_code_at.js';
 import { error } from '../../errors.js';
 import { create_fragment } from './utils/create.js';
 import read_options from './read/options.js';
+import { getLocator } from 'locate-character';
 
 const regex_position_indicator = / \(\d+:\d+\)$/;
 
@@ -41,13 +42,16 @@ export class Parser {
 	/** @type {LastAutoClosedTag | undefined} */
 	last_auto_closed_tag;
 
+	locate;
+
 	/** @param {string} template */
 	constructor(template) {
 		if (typeof template !== 'string') {
 			throw new TypeError('Template must be a string');
 		}
 
 		this.template = template.trimEnd();
+		this.locate = getLocator(this.template, { offsetLine: 1 });
 
 		let match_lang;
 
@@ -133,6 +137,18 @@ export class Parser {
 		}
 	}
 
+	/**
+	 * offset -> line/column
+	 * @param {number} start
+	 * @param {number} end
+	 */
+	get_location(start, end) {
+		return {
+			start: /** @type {import('locate-character').Location_1} */ (this.locate(start)),
+			end: /** @type {import('locate-character').Location_1} */ (this.locate(end))
+		};
+	}
+
 	current() {
 		return this.stack[this.stack.length - 1];
 	}
@@ -297,7 +313,6 @@ export class Parser {
  */
 export function parse(template) {
 	const parser = new Parser(template);
-
 	return parser.root;
 }
 

packages/svelte/src/compiler/phases/1-parse/read/context.js

@@ -28,6 +28,7 @@ export default function read_pattern(parser) {
 			type: 'Identifier',
 			name,
 			start,
+			loc: parser.get_location(start, parser.index),
 			end: parser.index,
 			typeAnnotation: annotation
 		};