Funicular doesn't filter output acorrding to output-schema

[Damirados]

If there are keys in map returned by handler that are not present in output schema funicular will not filter them out.

[retro]

@Damirados Funicular shouldn't do it. It will just ensure that returned value is valid as per schema. Since Malli schemas are open by default you can have extra keys in the returned map(s). One solution might be to use closed Malli schemas

[Damirados]

That is kinda inconvenient. What will closed Malli schema do? Will it just throw validation error or will it filter it.

It would be nice to have insurance that what comes over wire never exceeds what's in the schema. Otherwise we have to process data in handler both on input and output which IMO opens up room for error and/or security issues.

[retro]

It will throw the error.

If you’re interested in working on this feature, we can definitely include it in funicular

[Damirados]

Sure. It would be sensible default with configuration option to disable it because some app may rely on current behavior.

I would benefit from introductory course into funicular code base before I start work on that.

[retro]

This is actually more related to Malli than to Funicular - adding it to Funicular will be a pretty simple case of adding another interceptor. What we need to do is:

1. Figure out how to compare Malli schemas so that given a vector of schemas: [schema1, schema2, schema3], schema2 and schema3 are a subset of schema1. There can be multiple output schemas defined (on different context levels) and we want them to be compatible. Only schema1 should be closed
2. Figure out how to filter data based on the Malli schema, and if there are any limitations related to this. For instance schemas can be combined, and there can be multiple ways of expressing similar things

With these two things in place, we should be able to generate a function that walks through the data and filters out things that are not needed