.data() returns by reference instead of a copy, causing the outside to be likely to corrupt the guts on write

[StoneCypher]

ugh

john@LAPTOP-PE9BBGOJ MINGW64 ~/projects/jssm (main)
$ node

Welcome to Node.js v22.1.0.
Type ".help" for more information.

> const j = require('.');
undefined

> const m = j.from('a -> b;', { data: { test: 'oldval' } });
undefined

> m.data();
{ test: 'oldval' }

> const z = m.data();
undefined

> z;
{ test: 'oldval' }

> z.test = 'newval';
'newval'

> m.data();
{ test: 'newval' }

the data inside m was changed because:

1. m.data() returns its internal storage, instead of a copy thereof
2. we assigned that to z
3. we altered z, which is a reference to m._data
4. that mutates m._data, which is almost certainly unintentional

this isn't strictly a bug, but, it violates the principle of least surprise at a level that'll get The Hague's attention

modifying to return a copy, but, this invokes the javascript "what kind of copy" nightmare, which may reflect a need for functional parameterization or to emphasize using a self-manageable class

everything is terrible, especially everything