patternProperties: skip keys with undefined values

[YellowKirby]

What issue does this pull request resolve?

Fixes #1173

When iterating over object keys that match patternProperties, ignore keys whose data values that are undefined. This makes it consistent with how regular properties are handled.

What changes did you make?

In properties.jst, when iterating over properties in an object, check both that the property key matches the given RegExp (this check is not new) and that the data value is not undefined (this part is new).

Is there anything that requires more attention while reviewing?

First time making changes to this codebase. Not sure if there's anything I missed.

[epoberezkin]

@YellowKirby thanks for the PR and sorry for the delay.

I am a bit reluctant to fix it without major version change and even more reluctant doing it piece by piece.

There are quite a few cases where undefined properties would be used, depending on ownProperties option - check out other places where iterateProperties is used and also noPropertyInData - so probably easier to fix there. Both are defined in definitions.def. Also there is required keyword - not sure what is the current behaviour, it would depend on some other options...

To do it comprehensively, in the current major version, some option (e.g. validateUndefined) should be added:

• without option: keep current behaviour for all keywords, accounting for ownProperties option.
• false: ignore undefined properties for all keywords
• true: take undefined properties into account for all keywords

It will result in a much bigger test case.

[YellowKirby]

Thank you for the feedback! I think adding a new option makes a lot of sense. I can work on adding that as well as checking more edge cases/combinations with other options when I get some free time.

[epoberezkin]

closing it, the code moved to TS