From 044dce9da54cdf2dc1c8d268038364c4ac22b110 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Wed, 7 Jan 2026 18:37:01 +0000
Subject: [PATCH] fix: adjust `loc` property of `Program` nodes created from
 `<script>` elements (#17428)

* fix: adjust program location to prevent corrupted sourcemaps

* update changeset

* go the other way
---
 .changeset/tall-phones-fix.md                            | 5 +++++
 .../svelte/src/compiler/phases/1-parse/read/script.js    | 9 ++++++++-
 .../parser-legacy/samples/binding-shorthand/output.json  | 2 +-
 .../tests/parser-legacy/samples/binding/output.json      | 2 +-
 .../parser-legacy/samples/dynamic-import/output.json     | 2 +-
 .../samples/each-block-destructured/output.json          | 2 +-
 .../parser-legacy/samples/generic-snippets/output.json   | 2 +-
 .../samples/javascript-comments/output.json              | 2 +-
 .../svelte/tests/parser-legacy/samples/refs/output.json  | 2 +-
 .../script-attribute-with-curly-braces/output.json       | 2 +-
 .../samples/script-comment-only/output.json              | 2 +-
 .../samples/script-context-module-unquoted/output.json   | 6 +++---
 .../tests/parser-legacy/samples/script/output.json       | 2 +-
 .../samples/whitespace-after-script-tag/output.json      | 4 ++--
 .../samples/comment-before-function-binding/output.json  | 2 +-
 .../samples/comment-before-script/output.json            | 4 ++--
 .../parser-modern/samples/generic-snippets/output.json   | 2 +-
 .../samples/loose-valid-each-as/output.json              | 2 +-
 .../tests/parser-modern/samples/options/output.json      | 8 ++++----
 .../samples/script-style-no-markup/output.json           | 2 +-
 .../tests/parser-modern/samples/snippets/output.json     | 2 +-
 .../samples/typescript-in-event-handler/output.json      | 2 +-
 22 files changed, 40 insertions(+), 28 deletions(-)
 create mode 100644 .changeset/tall-phones-fix.md

diff --git a/.changeset/tall-phones-fix.md b/.changeset/tall-phones-fix.md
new file mode 100644
index 0000000000..29e57c060f
--- /dev/null
+++ b/.changeset/tall-phones-fix.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: adjust `loc` property of `Program` nodes created from `<script>` elements
diff --git a/packages/svelte/src/compiler/phases/1-parse/read/script.js b/packages/svelte/src/compiler/phases/1-parse/read/script.js
index 9ce449f200..db3c50a8d1 100644
--- a/packages/svelte/src/compiler/phases/1-parse/read/script.js
+++ b/packages/svelte/src/compiler/phases/1-parse/read/script.js
@@ -6,6 +6,7 @@ import { regex_not_newline_characters } from '../../patterns.js';
 import * as e from '../../../errors.js';
 import * as w from '../../../warnings.js';
 import { is_text_attribute } from '../../../utils/ast.js';
+import { locator } from '../../../state.js';
 
 const regex_closing_script_tag = /<\/script\s*>/;
 const regex_starts_with_closing_script_tag = /^<\/script\s*>/;
@@ -39,9 +40,15 @@ export function read_script(parser, start, attributes) {
 		parser.acorn_error(err);
 	}
 
-	// TODO is this necessary?
 	ast.start = script_start;
 
+	if (ast.loc) {
+		// Acorn always uses `0` as the start of a `Program`, but for sourcemap purposes
+		// we need it to be the start of the `<script>` contents
+		({ line: ast.loc.start.line, column: ast.loc.start.column } = locator(start));
+		({ line: ast.loc.end.line, column: ast.loc.end.column } = locator(parser.index));
+	}
+
 	/** @type {'default' | 'module'} */
 	let context = 'default';
 
diff --git a/packages/svelte/tests/parser-legacy/samples/binding-shorthand/output.json b/packages/svelte/tests/parser-legacy/samples/binding-shorthand/output.json
index 9c48025ff9..711bd54525 100644
--- a/packages/svelte/tests/parser-legacy/samples/binding-shorthand/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/binding-shorthand/output.json
@@ -63,7 +63,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/binding/output.json b/packages/svelte/tests/parser-legacy/samples/binding/output.json
index 17a78f051c..b103e03683 100644
--- a/packages/svelte/tests/parser-legacy/samples/binding/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/binding/output.json
@@ -73,7 +73,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/dynamic-import/output.json b/packages/svelte/tests/parser-legacy/samples/dynamic-import/output.json
index ee19d58742..76bb6c7eb6 100644
--- a/packages/svelte/tests/parser-legacy/samples/dynamic-import/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/dynamic-import/output.json
@@ -21,7 +21,7 @@
 				},
 				"end": {
 					"line": 9,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/each-block-destructured/output.json b/packages/svelte/tests/parser-legacy/samples/each-block-destructured/output.json
index 637da24aea..684051e304 100644
--- a/packages/svelte/tests/parser-legacy/samples/each-block-destructured/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/each-block-destructured/output.json
@@ -190,7 +190,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/generic-snippets/output.json b/packages/svelte/tests/parser-legacy/samples/generic-snippets/output.json
index 9cb5d765e8..76605f5192 100644
--- a/packages/svelte/tests/parser-legacy/samples/generic-snippets/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/generic-snippets/output.json
@@ -258,7 +258,7 @@
 				},
 				"end": {
 					"line": 2,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [],
diff --git a/packages/svelte/tests/parser-legacy/samples/javascript-comments/output.json b/packages/svelte/tests/parser-legacy/samples/javascript-comments/output.json
index 4723564f17..3775c48228 100644
--- a/packages/svelte/tests/parser-legacy/samples/javascript-comments/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/javascript-comments/output.json
@@ -298,7 +298,7 @@
 				},
 				"end": {
 					"line": 31,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/refs/output.json b/packages/svelte/tests/parser-legacy/samples/refs/output.json
index 7f30946fc5..1e8efe78f8 100644
--- a/packages/svelte/tests/parser-legacy/samples/refs/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/refs/output.json
@@ -73,7 +73,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/script-attribute-with-curly-braces/output.json b/packages/svelte/tests/parser-legacy/samples/script-attribute-with-curly-braces/output.json
index e0b50e3b92..4ad004c88a 100644
--- a/packages/svelte/tests/parser-legacy/samples/script-attribute-with-curly-braces/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/script-attribute-with-curly-braces/output.json
@@ -73,7 +73,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/script-comment-only/output.json b/packages/svelte/tests/parser-legacy/samples/script-comment-only/output.json
index b04a823e8d..0f7d0b8465 100644
--- a/packages/svelte/tests/parser-legacy/samples/script-comment-only/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/script-comment-only/output.json
@@ -37,7 +37,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [],
diff --git a/packages/svelte/tests/parser-legacy/samples/script-context-module-unquoted/output.json b/packages/svelte/tests/parser-legacy/samples/script-context-module-unquoted/output.json
index 64250cb302..34a640200c 100644
--- a/packages/svelte/tests/parser-legacy/samples/script-context-module-unquoted/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/script-context-module-unquoted/output.json
@@ -24,12 +24,12 @@
 			"end": 77,
 			"loc": {
 				"start": {
-					"line": 1,
+					"line": 5,
 					"column": 0
 				},
 				"end": {
 					"line": 7,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
@@ -84,7 +84,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/script/output.json b/packages/svelte/tests/parser-legacy/samples/script/output.json
index d3d4abd6b2..14d2805216 100644
--- a/packages/svelte/tests/parser-legacy/samples/script/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/script/output.json
@@ -73,7 +73,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-legacy/samples/whitespace-after-script-tag/output.json b/packages/svelte/tests/parser-legacy/samples/whitespace-after-script-tag/output.json
index 69b2382442..8853c32f9c 100644
--- a/packages/svelte/tests/parser-legacy/samples/whitespace-after-script-tag/output.json
+++ b/packages/svelte/tests/parser-legacy/samples/whitespace-after-script-tag/output.json
@@ -72,8 +72,8 @@
 					"column": 0
 				},
 				"end": {
-					"line": 3,
-					"column": 0
+					"line": 8,
+					"column": 1
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-modern/samples/comment-before-function-binding/output.json b/packages/svelte/tests/parser-modern/samples/comment-before-function-binding/output.json
index 13cc5fea7b..27692e98b4 100644
--- a/packages/svelte/tests/parser-modern/samples/comment-before-function-binding/output.json
+++ b/packages/svelte/tests/parser-modern/samples/comment-before-function-binding/output.json
@@ -272,7 +272,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-modern/samples/comment-before-script/output.json b/packages/svelte/tests/parser-modern/samples/comment-before-script/output.json
index 8d77165297..8840aad85a 100644
--- a/packages/svelte/tests/parser-modern/samples/comment-before-script/output.json
+++ b/packages/svelte/tests/parser-modern/samples/comment-before-script/output.json
@@ -34,12 +34,12 @@
 			"end": 67,
 			"loc": {
 				"start": {
-					"line": 1,
+					"line": 2,
 					"column": 0
 				},
 				"end": {
 					"line": 4,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-modern/samples/generic-snippets/output.json b/packages/svelte/tests/parser-modern/samples/generic-snippets/output.json
index 8e1654feed..f29eb6fc72 100644
--- a/packages/svelte/tests/parser-modern/samples/generic-snippets/output.json
+++ b/packages/svelte/tests/parser-modern/samples/generic-snippets/output.json
@@ -296,7 +296,7 @@
 				},
 				"end": {
 					"line": 2,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [],
diff --git a/packages/svelte/tests/parser-modern/samples/loose-valid-each-as/output.json b/packages/svelte/tests/parser-modern/samples/loose-valid-each-as/output.json
index b428cff0b2..441cf71519 100644
--- a/packages/svelte/tests/parser-modern/samples/loose-valid-each-as/output.json
+++ b/packages/svelte/tests/parser-modern/samples/loose-valid-each-as/output.json
@@ -227,7 +227,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [
diff --git a/packages/svelte/tests/parser-modern/samples/options/output.json b/packages/svelte/tests/parser-modern/samples/options/output.json
index 08ce8d43b7..c220811175 100644
--- a/packages/svelte/tests/parser-modern/samples/options/output.json
+++ b/packages/svelte/tests/parser-modern/samples/options/output.json
@@ -111,12 +111,12 @@
 			"end": 93,
 			"loc": {
 				"start": {
-					"line": 1,
+					"line": 3,
 					"column": 0
 				},
 				"end": {
 					"line": 4,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [],
@@ -182,12 +182,12 @@
 			"end": 160,
 			"loc": {
 				"start": {
-					"line": 1,
+					"line": 6,
 					"column": 0
 				},
 				"end": {
 					"line": 7,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [],
diff --git a/packages/svelte/tests/parser-modern/samples/script-style-no-markup/output.json b/packages/svelte/tests/parser-modern/samples/script-style-no-markup/output.json
index b5e42e9217..db58a62148 100644
--- a/packages/svelte/tests/parser-modern/samples/script-style-no-markup/output.json
+++ b/packages/svelte/tests/parser-modern/samples/script-style-no-markup/output.json
@@ -93,7 +93,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [],
diff --git a/packages/svelte/tests/parser-modern/samples/snippets/output.json b/packages/svelte/tests/parser-modern/samples/snippets/output.json
index c217ef94e9..f358e2a60c 100644
--- a/packages/svelte/tests/parser-modern/samples/snippets/output.json
+++ b/packages/svelte/tests/parser-modern/samples/snippets/output.json
@@ -230,7 +230,7 @@
 				},
 				"end": {
 					"line": 1,
-					"column": 18
+					"column": 27
 				}
 			},
 			"body": [],
diff --git a/packages/svelte/tests/parser-modern/samples/typescript-in-event-handler/output.json b/packages/svelte/tests/parser-modern/samples/typescript-in-event-handler/output.json
index a1d6ed56bf..7b521513f4 100644
--- a/packages/svelte/tests/parser-modern/samples/typescript-in-event-handler/output.json
+++ b/packages/svelte/tests/parser-modern/samples/typescript-in-event-handler/output.json
@@ -396,7 +396,7 @@
 				},
 				"end": {
 					"line": 3,
-					"column": 0
+					"column": 9
 				}
 			},
 			"body": [