RicoSuter/NJsonSchema

Propagate item-level validation on string arrays from JSON schema to C# object model

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#1,292 opened on Dec 8, 2020

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help wantedproject: NJsonSchema.CodeGeneration.CSharptype: enhancement

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Description

I have a string array field which validates not only the length of the array, but the length of the strings in the array as well:

"Tags": {
      "type": "array",
      "minItems": 1,
      "maxItems": 16,
      "items": {
        "type": "string",
        "minLength": 1,
        "maxLength": 3
      }
    },

However, when converted to a C# OM, the per-item validation gets lost:

[Newtonsoft.Json.JsonProperty("Tags", Required = Newtonsoft.Json.Required.DisallowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
[System.ComponentModel.DataAnnotations.MinLength(1)]
[System.ComponentModel.DataAnnotations.MaxLength(16)]
public System.Collections.Generic.ICollection<string> Tags { get; set; }

I don't have a bright idea on how this validation criteria could live in the .NET world, it's possible that there's no way to currently phrase that using the DataAnnotations, but I'm hoping to be surprised!

Contributor guide

Research direction
Examine how NJsonSchema generates C# code for array properties with item schemas. Focus on the code generation path that emits DataAnnotations attributes. Look for existing support for other item level validations (e.g., pattern) and extend it to minLength/maxLength. The JSON Schema specification defines these properties on item schemas; the generator needs to map them to appropriate .NET attributes or custom validation.
Tech stack
csharp
Domain
backendtooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C#JSON Schema
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50