Reading an empty array ('{}') throws RangeError: Invalid array length and leaves the connection unusable #129

Note: I tracked this down with the help of Claude Code (an AI coding assistant). I ran the repro below myself, and the analysis was checked against the ts-postgres and PostgreSQL sources linked here.

Version: ts-postgres 2.0.4 (the same code is still on master), Node.js v22.23.4, PostgreSQL 13

Repro

import { connect } from 'ts-postgres';

const client = await connect({ /* ... */ });
console.log((await client.query("SELECT '{a}'::text[] AS a")).rows); // [ [ [ 'a' ] ] ]

try {
  await client.query("SELECT '{}'::text[] AS a");
} catch (e) {
  console.log(e.message); // "Invalid array length"
}
console.log(client.closed); // false

await client.query('SELECT 1'); // rejects with "Stream not writable"

Log output:

ts-postgres: RangeError: Invalid array length
ts-postgres: Cancelled query due to an internal error

Expected: [ [ [] ] ], i.e. the column decodes to an empty array, and the connection stays usable.

Actual:

1. The query rejects with RangeError: Invalid array length.
2. The client destroys its stream (this.stream.destroy() in receive()), but client.closed stays false. A pool that checks closed to validate connections, like generic-pool with validate: c => !c.closed, keeps handing out the dead connection. Every later query on it fails with Stream not writable.

Cause

PostgreSQL represents an empty array as a zero-dimensional array (“an empty (zero-dimensional) array”, 8.15.3. Accessing Arrays), so in the binary format it arrives as ndim = 0 with no dimension headers. The decoder in readRowData computes

const dimCount = buffer.readInt32BE(offset) - 1;

which is -1 for an empty array. That is not 0, so it takes the multi-dimensional branch and calls new Array(dimCount), i.e. new Array(-1).

Suggested fix: when ndim is 0, return [] before branching on dimCount. Separately, it would help if closed became true after the stream is destroyed on an internal error.

Workaround: select the column through array_to_json(col). It comes back as json, so an empty array decodes to [] and NULL to null.