Implement Draft 2019-09

[Stranger6667]

Validation docs: https://tools.ietf.org/html/draft-handrews-json-schema-validation-02

New keywords:

• $anchor
• $definitions
• $recursiveRef
• $recursiveAnchor
• Implement unevaluatedItems #287
• Implement unevaluatedProperties #288
• contentSchema
• maxContains
• minContains
• deprecated
• Implement dependentRequired & dependentSchemas #286 (instead of dependencies)

Implementation examples - TypeScript, Python (partial)

[aexvir]

Looking forward to have this available 🙂️

[Stranger6667]

Hope to get back to this feature soon :)

[fimbault]

Now there's Draft 2020-12

[alexjg]

We should be able to implement both 2019-09 and 2020-12 in one go I think. Here's my understanding of the work to be done:

Work to be done

Based on the changes from Draft-07 to 2019-09

Annotations, errors and outputs

• Implement collection of annotations whilst evaluating schemas
• Implement the "basic" output format to provide access to collected
  annotations

Core vocabulary changes

• Split the various keywords into different vocabularies and implement
  processing of the $vocabulary keyword to determine which keywords are
  available to a schema
• Implement $anchor keyword
• Disallow use of fragments in $id (that usecase being taken up by $anchor)
• Implement $definitions keyword
• Implement $recursiveRef and $recursiveAnchor (these are renamed to
  $dynamicRef and $dynamicAnchor in 2020-12 but the latter is a superset of
  the former so we can use the same implementation)

Applicator Vocabulary

• Split dependencies into dependentSchemas and dependentRequired
• Implement unevaluatedItems and unevaluatedProperties

Format changes

• Add an option to turn off processing of the format keyword and instead
  merely make it available as an annotation
• Implement the duration and uuid format validators
• Make contentEncoding available as an annotation and not as an assertion
• Implement the contentSchema keyword

Validation

• Implement maxContains and minContains

Meta-data

• Implement deprecated

Based on changes from 2019-09 to 2020-12

• replace items and additionalItems with prefixItems and ites
• implement $dynamicRef and $dynamicAnchor (see above re. $recursive* versions)

Common components

• Ensure that items which pass a contains schema are not processed by an
  unevaluatedItems schema. This is not specified in 2019-09 but is compatible

[Stranger6667]

Great write-up, @alexjg !

I have some small bits here and there (maybe incomplete):

• minContains & maxContains - 16b7518
• depentRequired - 9410582

Here is also some existing (but not yet merged) implementation for needed keywords. It might help to implement those keywords here.

I like the plan and would be happy to split it into granular tasks! I'll also check it in more detail in a few days.

I think some changes could be done and merged, but we may not expose them (e.g. new keyword impls) until their respective drafts are ready. So, there should be no problem with accumulating changes step-by-step. Though, we can still test them high-level via some cfg(test) items - e.g. conditional Draft201909 enum variant.

What do you think if we approach the implementation this way?

[alexjg]

That seems like a sensible way to proceed. I'm going to make a start on the annotation collection and output formatting part as that feels like it's the largest change architecturally.

[Stranger6667]

Great!

Here are separate issues for the entries above.

2019-09

Annotations, errors and outputs

• Collect annotations whilst evaluating schemas #262
• Implement output formatting from Draft 2019-09 #100
• Make contentEncoding available as an annotation and not as an assertion #267

Core vocabulary changes

• Split keywords into different vocabularies & process $vocabulary #263
• Disallow use of fragments in $id #264

Format changes

• Option to turn off processing of the format keyword #261
• Implement the duration format validator #265
• Implement the uuid format validator #266

I added new keyword implementation as sub-tasks in existing issues for their relevant drafts (this one and #195 ).

[Stranger6667]

I'll set up conditional compilation for testing & merge existing keywords implementation, so we can run tests & add new one easier. It should be pretty much isolated, so I hope we can avoid conflicting changes.