From beb71e81de517acba7849cf90e10d29d7d4cefa7 Mon Sep 17 00:00:00 2001
From: adiguba <frederic.martini@gmail.com>
Date: Thu, 27 Aug 2026 06:59:03 +0200
Subject: [PATCH] preserve original location

---
 packages/svelte/src/compiler/index.js         |  2 +-
 .../src/compiler/phases/1-parse/index.js      |  5 ++--
 .../client/transform-template/index.js        |  2 +-
 packages/svelte/src/compiler/state.js         | 24 +++++++++++++++----
 4 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/packages/svelte/src/compiler/index.js b/packages/svelte/src/compiler/index.js
index 599206ac6a..9e833b59d6 100644
--- a/packages/svelte/src/compiler/index.js
+++ b/packages/svelte/src/compiler/index.js
@@ -26,7 +26,7 @@ export function compile(source, options) {
 
 	const validated = validate_component_options(options, '');
 
-	let parsed = _parse(source);
+	let parsed = _parse(source, false, options.sourcemap);
 
 	const { customElement: customElementOptions, ...parsed_options } = parsed.options || {};
 
diff --git a/packages/svelte/src/compiler/phases/1-parse/index.js b/packages/svelte/src/compiler/phases/1-parse/index.js
index fa7b292640..61db00263f 100644
--- a/packages/svelte/src/compiler/phases/1-parse/index.js
+++ b/packages/svelte/src/compiler/phases/1-parse/index.js
@@ -327,10 +327,11 @@ export class Parser {
 /**
  * @param {string} template
  * @param {boolean} [loose]
+ * @param {object | string} [sourcemap]
  * @returns {AST.Root}
  */
-export function parse(template, loose = false) {
-	state.set_source(template);
+export function parse(template, loose = false, sourcemap) {
+	state.set_source(template, sourcemap);
 
 	const parser = new Parser(template, loose);
 	return parser.root;
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/transform-template/index.js b/packages/svelte/src/compiler/phases/3-transform/client/transform-template/index.js
index 5fdc88844b..5c818b185f 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/transform-template/index.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/transform-template/index.js
@@ -15,7 +15,7 @@ function build_locations(nodes) {
 	for (const node of nodes) {
 		if (node.type !== 'element') continue;
 
-		const { line, column } = locator(node.start);
+		const { line, column } = locator(node.start, true);
 
 		const expression = b.array([b.literal(line), b.literal(column)]);
 		const children = build_locations(node.children);
diff --git a/packages/svelte/src/compiler/state.js b/packages/svelte/src/compiler/state.js
index 5ae001ec50..02f2853404 100644
--- a/packages/svelte/src/compiler/state.js
+++ b/packages/svelte/src/compiler/state.js
@@ -1,6 +1,7 @@
 /** @import { Location } from 'locate-character' */
 /** @import { CompileOptions } from './types' */
 /** @import { AST, Warning } from '#compiler' */
+import { TraceMap, originalPositionFor } from '@jridgewell/trace-mapping';
 import { getLocator } from 'locate-character';
 import { sanitize_location } from '../utils.js';
 
@@ -46,20 +47,33 @@ export let dev;
 
 export let runes = false;
 
-/** @type {(index: number) => Location} */
+/** @type {(index: number, use_sourcemap?: boolean) => Location} */
 export let locator;
 
-/** @param {string} value */
-export function set_source(value) {
+/**
+ * @param {string} value
+ * @param {object | string} [sourcemap]
+ */
+export function set_source(value, sourcemap) {
 	source = value;
 	source_lines = source.split('\n');
 
+	const map = (sourcemap && typeof sourcemap === 'object')
+		? new TraceMap( /** @type {any} */ (sourcemap))
+		: null;
+
 	const l = getLocator(source, { offsetLine: 1 });
 
-	locator = (i) => {
+	locator = (i, use_sourcemap=false) => {
 		const loc = l(i);
 		if (!loc) throw new Error('An impossible situation occurred');
-
+		if (use_sourcemap && map) {
+			const original = originalPositionFor(map, loc);
+			if (original.line != null && original.column != null) {
+				loc.line = original.line;
+				loc.column = original.column;
+			}
+		}
 		return loc;
 	};
 }