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error printer: one render per error, [Circular] under the key that closes the cycle #37270

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error printer: one render per error, [Circular] under the key that closes the cycle #37270

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f2c583d
error printer: one render per error, [Circular] under the key that cl…
robobun Sep 27, 2026
9638e77
error printer: the cause loop needs no check for an error that is bei…
robobun Sep 28, 2026
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38 changes: 16 additions & 22 deletions src/jsc/ConsoleObject.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1910,6 +1910,10 @@ pub mod formatter {
| Tag::Event
)
}

pub(crate) fn is_recorded_by_its_printer(self) -> bool {
matches!(self, Tag::Error)
}
}

/// Only `CustomFormattedObject` carries a payload.
Expand Down Expand Up @@ -3226,6 +3230,11 @@ pub mod formatter {
let _ = self.map.remove(&value);
}

#[inline]
pub(crate) fn visited_contains(&self, value: JSValue) -> bool {
self.map_node.is_some() && self.map.contains(&value)
}

/// Circular-reference / stack-overflow / visited-map prelude for
/// `print_as`. Outlined so its locals (the pool node, the
/// `get_or_put` result, the `[Circular]` write path) live in a leaf
Expand All @@ -3240,7 +3249,7 @@ pub mod formatter {
&mut self,
writer_: &mut dyn bun_io::Write,
value: JSValue,
can_circ: bool,
format: Tag,
remove_before_recurse: &mut bool,
) -> JsResult<bool> {
if self.failed {
Expand All @@ -3249,7 +3258,7 @@ pub mod formatter {
if self.global_this.has_exception() {
return Err(jsc::JsError::Thrown);
}
if !can_circ {
if !format.can_have_circular_references() {
return Ok(true);
}

Expand All @@ -3261,6 +3270,10 @@ pub mod formatter {
return Ok(false);
}

if format.is_recorded_by_its_printer() {
return Ok(true);
}

if !self.visited_insert(value) {
if writer_
.write_all(pfmt!("<r><cyan>[Circular]<r>", C).as_bytes())
Expand Down Expand Up @@ -3289,7 +3302,7 @@ pub mod formatter {
if !self.print_as_prelude::<ENABLE_ANSI_COLORS>(
writer_,
value,
format.can_have_circular_references(),
format,
&mut remove_before_recurse,
)? {
return Ok(());
Expand Down Expand Up @@ -3861,25 +3874,6 @@ pub mod formatter {
writer_: &mut dyn bun_io::Write,
value: JSValue,
) -> JsResult<()> {
// Temporarily remove from the visited map to allow
// printErrorlikeObject to process it. The circular reference
// check is already done in print_as, so we know it's safe.
let was_in_map = if self.map_node.is_some() {
self.map.remove(&value).is_some()
} else {
false
};
let map_restore_ptr: *mut visited::Map = &raw mut self.map;
scopeguard::defer! {
// SAFETY: `self.map` outlives this guard; no other borrow is
// live at the drop point.
unsafe {
if was_in_map {
let _ = (*map_restore_ptr).insert(value, ());
}
}
}

let mut adapter = DynWriteAdapter::new(&mut *writer_);
// SAFETY: per-thread VM.
let vm = VirtualMachine::get().as_mut();
Expand Down
79 changes: 63 additions & 16 deletions src/jsc/VirtualMachine.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5944,7 +5944,20 @@ impl VirtualMachine {
let writer = unsafe { &mut *ctx.writer };
ctx.printed_member = true;
formatter.depth = formatter.depth.saturating_add(1);
if formatter.depth > formatter.error_chain_max_depth()
if next_value.is_cell()
&& next_value.js_type() == crate::JSType::ErrorInstance
&& formatter.visited_contains(next_value)
{
let _ = if ctx.allow_ansi_color {
writer.write_all(
bun_core::pretty_fmt!("<r><cyan>[Circular]<r>\n", true).as_bytes(),
)
} else {
writer.write_all(
bun_core::pretty_fmt!("<r><cyan>[Circular]<r>\n", false).as_bytes(),
)
};
} else if formatter.depth > formatter.error_chain_max_depth()
|| !formatter.stack_check.is_safe_to_recurse()
{
let _ = if ctx.allow_ansi_color {
Expand Down Expand Up @@ -6611,6 +6624,7 @@ impl VirtualMachine {
) -> crate::CrateResult<()> {
let mut default_formatter = crate::console_object::Formatter::new(self.global());
let f = formatter.unwrap_or(&mut default_formatter);
let mut recorded = false;
self.print_error_instance_body(
zig_exception,
JSValue::ZERO,
Expand All @@ -6619,6 +6633,7 @@ impl VirtualMachine {
writer,
allow_ansi_color,
allow_side_effects,
&mut recorded,
)
// `defer default_formatter.deinit()` → Drop.
}
Expand Down Expand Up @@ -6667,6 +6682,18 @@ impl VirtualMachine {
return Ok(());
}

if error_instance.is_cell()
&& error_instance.js_type() == crate::JSType::ErrorInstance
&& formatter.visited_contains(error_instance)
{
writer.write_all(if allow_ansi_color {
bun_core::pretty_fmt!("<r><cyan>[Circular]<r>", true).as_bytes()
} else {
bun_core::pretty_fmt!("<r><cyan>[Circular]<r>", false).as_bytes()
})?;
return Ok(());
}
Comment thread
robobun marked this conversation as resolved.

// Note: `Holder` is ~4 KB (32 ZigStackFrames + 6 source lines +
// ZigException). It sits next to the large runtime-dispatched body, so
// box it to keep the per-level recursion frame small enough for the
Expand All @@ -6690,6 +6717,7 @@ impl VirtualMachine {
);
error_instance.ensure_still_alive();

let mut recorded = false;
let result = self.print_error_instance_body(
// SAFETY: see above.
unsafe { &mut *exception },
Expand All @@ -6700,7 +6728,11 @@ impl VirtualMachine {
writer,
allow_ansi_color,
allow_side_effects,
&mut recorded,
);
if recorded {
formatter.visited_remove(error_instance);
}

drop(source_code_slice);
exception_holder.deinit(self);
Expand All @@ -6722,6 +6754,7 @@ impl VirtualMachine {
writer: &mut bun_core::io::Writer,
allow_ansi_color: bool,
allow_side_effects: bool,
recorded: &mut bool,
) -> crate::CrateResult<()> {
use crate::JSType;
use crate::console_object::formatter::TagOptions;
Expand Down Expand Up @@ -7065,7 +7098,9 @@ impl VirtualMachine {
}

let kind = value.js_type();
if kind == JSType::ErrorInstance && !prev_had_errors {
let circular = kind == JSType::ErrorInstance
&& (value == error_instance || formatter.visited_contains(value));
if kind == JSType::ErrorInstance && !prev_had_errors && !circular {
if field.eq_ascii(b"cause") {
saw_cause = true;
}
Expand All @@ -7076,6 +7111,12 @@ impl VirtualMachine {
|| value.is_primitive()
|| kind.is_string_like()
{
if circular && field.eq_ascii(b"cause") {
saw_cause = true;
}
Comment thread
robobun marked this conversation as resolved.
if !*recorded && !value.is_primitive() {
*recorded = formatter.visited_insert(error_instance);
}
let prev_disable_inspect_custom = formatter.disable_inspect_custom;
let prev_quote_strings = formatter.quote_strings;
let prev_max_depth = formatter.max_depth;
Expand Down Expand Up @@ -7159,20 +7200,30 @@ impl VirtualMachine {
)?;
}

if !is_first_property {
writer.write_all(b"\n")?;
}

// "cause" is not enumerable, so the above loop won't see it.
if !saw_cause {
let key = bun_core::String::static_("cause");
if let Some(cause) = error_instance.get_own(global_ref, &key)? {
if cause.is_cell() && cause.js_type() == JSType::ErrorInstance {
cause.protect();
errors_to_append.push(cause);
if cause == error_instance || formatter.visited_contains(cause) {
let pad_left = longest_name.saturating_sub(b"cause".len());
is_first_property = false;
splat_space(writer, pad_left as u64)?;
pretty_write!(
writer,
" cause<r><d>:<r> <r><cyan>[Circular]<r><r><d>,<r>\n"
)?;
} else {
cause.protect();
errors_to_append.push(cause);
}
}
}
}

if !is_first_property {
writer.write_all(b"\n")?;
}
} else if error_instance != JSValue::ZERO {
// If you do `reportError([1,2,3])` we should still show something.
let tag = Tag::get_advanced(
Expand Down Expand Up @@ -7200,15 +7251,12 @@ impl VirtualMachine {
)?;
}

if !*recorded && !errors_to_append.is_empty() {
*recorded = formatter.visited_insert(error_instance);
}

let mut exception_list = exception_list;
for &err in &errors_to_append {
// Circular-ref guard for cause chains.
if !formatter.visited_insert(err) {
writer.write_all(b"\n")?;
pretty_write!(writer, "<r><cyan>[Circular]<r>")?;
continue;
}

writer.write_all(b"\n")?;
let prev_depth = formatter.depth;
formatter.depth = formatter.depth.saturating_add(1);
Expand All @@ -7226,7 +7274,6 @@ impl VirtualMachine {
)
};
formatter.depth = prev_depth;
formatter.visited_remove(err);
result?;
}

Expand Down
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