Summary

The file node's append mode can have stale error handler references when the write stream is reused across multiple messages.

Problem

In append mode with static filenames, the write stream is kept open and reused. The error handler is set up once but references the msg and done from the first write. If an error occurs during a later write, the wrong message context is used.

Severity

MEDIUM - Can cause incorrect error reporting or double done() calls when write errors occur.

Proposed Fix

Add per-write error handling with a writeDone flag:

var writeDone = false;
var handleWriteError = function(err) {
    if (!writeDone) {
        writeDone = true;
        node.wstream.removeListener('error', handleWriteError);
        node.error(RED._("file.errors.appendfail",{error:err.toString()}),msg);
        done();
    }
};
node.wstream.on('error', handleWriteError);
node.wstream.write(buf, function() {
    if (!writeDone) {
        writeDone = true;
        node.wstream.removeListener('error', handleWriteError);
        nodeSend(msg);
        done();
    }
});