Top-level type parser

[kyscott18]

It would be great to be able to set a custom type parser for postgres data types at an instance level in addition to the query level. I'd be happy to work on this pr, but wanted to get some input on how it should look first.

API

import { PGlite, types } from '@electric-sql/pglite';

const pg = await PGlite.create({
 parsers: {
    [types.TEXT]: (value) => value.toUpperCase(),
  },
});

// or 

const pg = await PGlite.create();
pg.setParser(types.TEXT, (value) => value.toUpperCase());

It should probably be one or the other, which one do you think fits in best?

Relevant examples

node-postgres

var types = require('pg').types;
types.setTypeParser(20, function(val) {
  return parseInt(val, 10)
});

drizzle-orm

const users = pgTable('users', {
  // set custom column type with ".$type"
  id: serial('id').$type<UserId>().primaryKey(),
});

[Ericnr]

this is very important for people trying to use PgLite for testing. We need to be able to match the way PgLite parses with the production driver

[jamesarosen]

const pg = await PGlite.create({
 parsers: {
    [types.TEXT]: (value) => value.toUpperCase(),
  },
});

One reason not to choose this approach is that whoever is creating the PGlite instance needs to know about type parsers and why they might override them:

// test-setup.ts
const client = await PGlite.create({
 parsers: {
    [types.TEXT]: (value) => value.toUpperCase(),
  },
});
const db = drizzle({ client });

For this reason, I recommend

pg.setParser(types.TEXT, (value) => value.toUpperCase());

or even mimic the node-postgres API directly given how popular that project is:

pg.setTypeParser(types.TEXT, (value) => value.toUpperCase());

That way, libraries like Drizzle can use the API to work around incompatibilities without having to push the work to the application developer.

[jadejr]

Doesn't this already exist? https://pglite.dev/docs/api or am I misunderstanding? It doesn't seem to have an instance method though as suggested. If that is what is really wanted, then the issue title should be adjusted.

[jamesarosen]

Great callout, @jadejr!

And although there's no instance method, there is a public setter. This fixes the issue with Drizzle:

const pglite = await PGlite.create({...})
const db = drizzle({ client });

// Fixes https://github.com/drizzle-team/drizzle-orm/issues/3997
client.serializers[types.JSON] = (value) => value;
client.serializers[types.JSONB] = (value) => value;

but this does not:

const pglite = await PGlite.create({
  serializers: {
    [types.JSON]: (value) => value,
    [types.JSONB]: (value) => value,
  }
})
const db = drizzle({ client })

because Drizzle (incorrectly) overrides the parsers. That's a Drizzle bug, but it shows the importance of flexibility here.