io-ts support

[Brettm12345]

I would love to see support for io-ts

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Thanks for your suggestion!

I've never touched io-ts. So I need to learn how to use it before working to support it.

It will take about two weeks (maybe).

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@Brettm12345 I may not be learning enough.

There are two things that I find difficult.

1. schema generation
2. support the directive

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Let me explain the first.

For example, yup (also zod) schema if you want to create a schema...

1. foo: String then types will be generated foo?: InputMaybe<Scalars['String']> and yup will be yup.string()
2. foo: String! then types will be generated foo: Scalars['String'] and yup will be yup.string().defined()

If I try to do the same thing with io-ts

1. foo: String then types will be generated foo?: InputMaybe<Scalars['String']> and io-ts will be t.string
2. foo: String! then types will be generated foo: Scalars['String'] and io-ts will be t.union([t.string, t.undefined, t.null])

In the case of yup (also zod), changes can be made in the form of extensions from the original schema. In contrast, io-ts seems to require the creation of a different schema in the first place.

Another critical problem is that 2. does not pass the type build. 😢

https://codesandbox.io/s/io-ts-optional-field-in-known-type-forked-bubkz?file=/src/index.ts

The second concern, as I mentioned earlier, is that the schemas are different, to begin with, so it will be difficult to apply.

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I'd like to know if you have any good ideas that could clear up these two issues. Pull requests are also welcome.

Thanks.

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If somebody is strongly required, welcome PR or your great idea.