From f6d8e2a08686d86b23177264be0120c615c75c28 Mon Sep 17 00:00:00 2001
From: robobun <117481402+robobun@users.noreply.github.com>
Date: Tue, 11 Aug 2026 04:36:43 +0000
Subject: [PATCH] ErrorInstance: record that addErrorInfo() attached a parser
 location (hasParseLocation)

Bun's stack formatter renders a synthetic "at <parse> (url:line)" frame
for SyntaxErrors whose line/sourceURL were recorded by the parser via
addErrorInfo(). Until now it recognized those errors by the sourceURL
being set, which is also true of structured-cloned errors (created with
their original's sourceURL) and of errors whose frames the GC finalizer
already flushed to a string (computeErrorInfo records the first frame's
URL), so giving either of those new frames with Error.captureStackTrace()
produced a bogus <parse> frame.

isParseError() cannot serve as the discriminator: it is also set for
eval-code syntax errors, which never go through addErrorInfo() and so
record no location, and toErrorObject() sets it only after addErrorInfo()
has already materialized the stack through the host hook.

Add a Bun-only bit that addErrorInfo() sets right where it records the
location, before materializing, and expose it as hasParseLocation().
---
 Source/JavaScriptCore/runtime/Error.cpp         | 3 +++
 Source/JavaScriptCore/runtime/ErrorInstance.cpp | 3 +++
 Source/JavaScriptCore/runtime/ErrorInstance.h   | 9 +++++++++
 3 files changed, 15 insertions(+)

diff --git a/Source/JavaScriptCore/runtime/Error.cpp b/Source/JavaScriptCore/runtime/Error.cpp
index b5514f770a289..1cc8c72a85add 100644
--- a/Source/JavaScriptCore/runtime/Error.cpp
+++ b/Source/JavaScriptCore/runtime/Error.cpp
@@ -262,6 +262,9 @@ JSObject* addErrorInfo(VM& vm, JSObject* error, int line, const SourceCode& sour
         if (!sourceURL.isEmpty()) {
             errorInstance->setSourceURL(sourceURL);
         }
+
+        // materializeErrorInfoIfNeeded() formats the stack through the host, which reads this.
+        errorInstance->setHasParseLocation();
 #endif
 
         errorInstance->materializeErrorInfoIfNeeded(vm);
diff --git a/Source/JavaScriptCore/runtime/ErrorInstance.cpp b/Source/JavaScriptCore/runtime/ErrorInstance.cpp
index 8cb916db573db..6f4afd6ef084f 100644
--- a/Source/JavaScriptCore/runtime/ErrorInstance.cpp
+++ b/Source/JavaScriptCore/runtime/ErrorInstance.cpp
@@ -48,6 +48,9 @@ ErrorInstance::ErrorInstance(VM& vm, Structure* structure, ErrorType errorType)
 #if ENABLE(WEBASSEMBLY)
     , m_catchableFromWasm(true)
 #endif // ENABLE(WEBASSEMBLY)
+#if USE(BUN_JSC_ADDITIONS)
+    , m_hasParseLocation(false)
+#endif
 {
 }
 
diff --git a/Source/JavaScriptCore/runtime/ErrorInstance.h b/Source/JavaScriptCore/runtime/ErrorInstance.h
index c28ce88fd7914..05d1bc01ac860 100644
--- a/Source/JavaScriptCore/runtime/ErrorInstance.h
+++ b/Source/JavaScriptCore/runtime/ErrorInstance.h
@@ -116,6 +116,12 @@ class ErrorInstance : public JSNonFinalObject {
     void setStackFrames(VM& vm, WTF::Vector<JSC::StackFrame>&& stackFrames);
     bool hasMaterializedErrorInfo() const { return m_errorInfoMaterialized; }
 
+    // Whether line()/sourceURL() were recorded by addErrorInfo() for a source the parser rejected, as
+    // opposed to copied from another error (structured clone) or derived from the stack frames. Unlike
+    // isParseError(), this is not set for parse errors that record no location (eval code), and it is
+    // set before the stack is materialized, so the host's stack formatter can rely on it.
+    bool hasParseLocation() const { return m_hasParseLocation; }
+    void setHasParseLocation() { m_hasParseLocation = true; }
 #endif
 
     JS_EXPORT_PRIVATE String sanitizedToString(JSGlobalObject*);
@@ -172,6 +178,9 @@ class ErrorInstance : public JSNonFinalObject {
 #if ENABLE(WEBASSEMBLY)
     bool m_catchableFromWasm : 1;
 #endif
+#if USE(BUN_JSC_ADDITIONS)
+    bool m_hasParseLocation : 1;
+#endif
 };
 
 String appendSourceToErrorMessage(CodeBlock*, BytecodeIndex, const String&, RuntimeType, ErrorInstance::SourceAppender);