Merge to support union schemas

[indifferentghost]

Hey,

I'm doing some validation on environment variables. Attempting something like the following:

const DevSchema = object({
  NODE_ENV: literal('production'),
  DATABASE_URL: string([toTrimmed(), minLength(1), url(), toLowerCase(), excludes('?tls=0')])
});

const ProdSchema = object({
  NODE_ENV: literal('development'),
  DATABASE_URL: string([toTrimmed(), minLength(1), url(), toLowerCase(), endsWith('?tls=0')])
});

const EnvSchema = merge([
  union([ DevSchema, ProdSchema ]),
  object({
    // shared config
    FOO_BAR: string()
  }),
])

Throws a lengthy TypeScript error that boils down to merge not supporting union schemas (and that's shown in the types right now.)

I looked and while I found references of it being implemented in 0.20.0.

I still unsure even what code to reference or how to build it.

[indifferentghost]

I ended up forcing descriminatedUnion the deprecation notice put me to variant, but I'm still unsure on the API of how to use this:

const EnvSchema = merge([
	object({ AUTH_SIGNED_COOKIE: string([toTrimmed(), minLength(1)]) }),
	variant('NODE_ENV', [DevEnvSchema, ProdEnvSchema])
	// union([DevEnvSchema, ProdEnvSchema]),
]);

[fabian-hiller]

As you can see here, descriminatedUnion is equal to variant. So please use variant instead. The idea of variant is to define the discriminator as the first argument and the union options as the second one. This way the validation is faster and the issues are more specific.

[fabian-hiller]

variant is basically a specialised version of union for objects.

[fabian-hiller]

Please try to use intersect for this use case. merge does only work for pure objects because it is able to truly merge objects together. For example, merge is able to overwrite individual entries.

const EnvSchema = intersect([
  union([DevSchema, ProdSchema]),
  object({
    // shared config
    FOO_BAR: string()
  }),
]);

[indifferentghost]

Works brilliantly! Thanks!

[indifferentghost]

Is there a reason to use a union over a variant in this senario?

const EnvSchema = intersect([
	object({ AUTH_SIGNED_COOKIE: string([toTrimmed(), minLength(1)]) }),
	variant('NODE_ENV', [DevEnvSchema, ProdEnvSchema])
]);

[fabian-hiller]

Whenever you work with objects and it is possible to use variant you should prefer it over union.

[fabian-hiller]

The reason is that the validation is faster and the output in case of any issues is more specific. Therefore, it is easier for you or your end users to fix the dataset.

[indifferentghost]

Whenever you work with objects and it is possible to use variant you should prefer it over union.

This is gold thank you