`console.log` does not print custom properties on empty arrays (inconsistent with Node.js)

[jinliming2]

What version of Bun is running?

1.2.22+6bafe2602

What platform is your computer?

Darwin 24.6.0 arm64 arm

What steps can reproduce the bug?

In Node.js, if you attach custom properties to an array, console.log will print both the array elements and the extra properties — even if the array is empty.

In Bun, the behaviour is inconsistent:

• For non-empty arrays, extra properties are printed as expected.
• For empty arrays, extra properties are not shown in the console output.

Example

// Case 1: empty array with extra property
const a = [];
a.field = 1;
console.log(a);

// Case 2: non-empty array with extra property
const b = [1, 2, 3];
b.field = 1;
console.log(b);

Node.js output

[ field: 1 ]
[ 1, 2, 3, field: 1 ]

Bun output

[]
[ 1, 2, 3, field: 1 ]

What is the expected behavior?

console.log should consistently print custom properties on arrays, regardless of whether the array is empty or not.
This would align with Node.js behaviour:

[ field: 1 ]
[ 1, 2, 3, field: 1 ]

What do you see instead?

In Bun, console.log omits the custom property when the array is empty:

[]
[ 1, 2, 3, field: 1 ]

Additional information

This issue impacts Bun’s SQL client (bun:sql).
For example:

• When sql`SELECT ...` returns non-empty results, console.log prints both the rows and the extra metadata fields (count, command, lastInsertRowid, affectedRows).
• When the result is an empty array, console.log prints only [] and does not show these metadata fields.
• Similarly, sql`UPDATE ...` often returns an empty array, and the metadata is not visible in console output.

This discrepancy makes debugging SQL queries more difficult compared to Node.js.

[linear]

ENG-20522 `console.log` does not print custom properties on empty arrays (inconsistent with Node.js)