Date-time format should use ISO 8601-1:2019 (same as System.Text.Json)

[cdecroix]

Environment

• Nuget Package: JsonSchema.Net
• Nuget Version: 4.0.3
• OS: Windows
• .Net Target: .Net 6.0

Describe the bug
Values like "2023-03-20 05:41:23.3881075" ("T" missing between the date and time) are valid in JsonSchema but it can't be deserialized by System.Text.Json.

According to the Microsoft documentation, they parse date using the ISO 8601-1:2019 format.
The regex added to JsonSchema in v4.0.1 is based on the previous version of that ISO.

Expected behavior
Validation should return an error.

[gregsdennis]

The JSON Schema spec, section 7.3.1 states RFC 3339. That's what this library uses.

[cdecroix]

Is it possible to override the format validation to match with System.Text.Json?

[gregsdennis]

You can create your own format implementation and override the default implementation.

The instructions are here.

Also, you may want to read that whole section, as it describes how to enable format validation.

Lastly, please be aware that providing date/time in a different format probably won't be compatible with other implementations, and you'll need to do this modification wherever you use this schema.

[gregsdennis]

Relevant: https://ijmacd.github.io/rfc3339-iso8601/

[gregsdennis]

This issue led me to look at the regex that was contributed to evaluate high-precision formats, and I discovered that that actually uses an ISO 8601 regex (which is what you were saying), which is wrong. I'll be updating that to support RFC3339.

I'm also opening an issue with .Net for deserialization support. I wouldn't be surprised if they come back with, "You can create a custom converter for DateTime." I'm not sure if that solves your issue, though.

[cdecroix]

Thanks for the clarification on which spec should be used!

For now, I overrode the validation in this lib to keep the same behavior as before (pre v4.0.1).

I did it by creating a ISchemaRefiner class that replace the format intent to use my custom validation method.
I didn't manage to create my own format class. The Validate was never called.

[gregsdennis]

I did it by creating a ISchemaRefiner class

This was reported as a JsonSchema.Net issue, however ISchemaRefiner is part of JsonSchema.Net.Generation. Had I known that you needed help with schema generation, my advice would have been different.

Regardless, while I'm glad that you got something working for your case, I'm not sure that this is fully resolved since there is a disparity between .Net's date-time format expectations and JSON Schema's date-time requirements.

[gregsdennis]

@cdecroix please see the latest comment in the dotnet/runtime discussion linked above. It appears there is some format crossover that you might be able to take advantage of.