Make validator serialization a first-class feature

[jdesrosiers]

#111 adds serialize/deserialize functions for compiled schemas. This issue would make it easy to serialize and restore a validator without having to use the low-level experimental API. This is what I'm thinking,

const validator = await validate("https://example.com/main");
const result1 = validator(42, "BASIC");

const json = validator.serialize();

const restoredValidator = restoreValidator(json);
const result2 = restoredValidator(42, "BASIC");

Is it too weird to have a function with properties? This is an interesting option because it allows for the possibility of validating both at runtime and when restored later without having to compile twice.

The alternative is to just have a dedicated function that serializes directly without building a validator function.

const json = await serializedValidator("https://example.com/main");
const restoredValidator = restoreValidator(json);
const result = restoredValidator(42, "BASIC");

[jdesrosiers]

Related to rjsf-team/react-jsonschema-form#4923

[Adityakumar37]

@jdesrosiers Hey, I took a look at the codebase to better understand what #112 would need. After going through core.js and the keyword plugins, the problem is pretty clear compile() produces an ast with a plugins Set that holds actual plugin objects (from dynamicRef, unevaluatedProperties, unevaluatedItems), and those are just functions, so they silently get dropped on JSON.stringify. Makes sense why #110 and #111 need to land first.
For #112 I'm thinking the public API would look something like:

// build step
const json = await compileValidator("https://example.com/main");
writeFileSync("validator.json", json);
// runtime (browser, no recompile)
const validator = restoreValidator(json, { customPlugins });
const result = validator(42, BASIC);

I have a few questions before diving in:

1 Should compileValidator/restoreValidator live under each dialect path (/draft-2020-12, /draft-07 etc.) or somewhere shared?
2 If a plugin has no id (since it's optional in #110), should compileValidator throw early rather than silently producing JSON that 3 can't be restored later?
Is a CLI tool for the build step in scope here or a separate issue? Feels like it's important for the rjsf use case specifically.

[jdesrosiers]

compileValidator is definitely not the right name. We already have a compile function and while the function would technically compile the schema, it's purpose is to "serialize" the compiled schema.

1 Should compileValidator/restoreValidator live under each dialect path (/draft-2020-12, /draft-07 etc.) or somewhere shared?

core.js is probably the right place to put it. I just needs to be exported in index.js to be available for every dialect.

2 If a plugin has no id (since it's optional in #110), should compileValidator throw early rather than silently producing JSON that 3 can't be restored later?

I think you answered your own question. I think it's obvious that producing JSON that can't be restored later isn't acceptable. But, that's not in scope for this issue. That's something the serialize function would from #111 would have to handle.

Is a CLI tool for the build step in scope here or a separate issue? Feels like it's important for the rjsf use case specifically.

No a CLI is not in scope.

[srivastava-diya]

Hey @jdesrosiers, since #115 is almost on the verge of completion i was thinking if it is okay for me to start working on this one,

Here's how i would approach it:

1. in lib/core.js i would modify the validate function so it returns a .serialize() method

    export const validate = async (url, value = undefined, options = undefined) => {
    const schema = await getSchema(url);
    const compiled = await compile(schema);
    const interpretAst = (value, options) => interpret(compiled, Instance.fromJs(value), options);
    interpretAst.serialize = () => serialize(compiled);
   
    return value === undefined ? interpretAst : interpretAst(value, options);
    };

2. in lib/core.js add a new restoreValidator(json) function

   export const restoreValidator = (json, options = undefined) => {
   const compiled = deserialize(json, options);
   const interpretAst = (value, options) => interpret(compiled, Instance.fromJs(value), options);
   interpretAst.serialize = () => serialize(compiled);
   
   return interpretAst;
   };

3. update the Validator type in lib/index.d.ts

4. Add restoreValidator to the main exports in lib/index.js

Also a quick question, should i also add tests?