PureYAML/Sources/PureYAMLJSON/JSON.BuiltinValidation.swift

import PureYAML

public extension PureYAML.Validation.BuiltinValidation {
    /// Reports any mapping key that is not a string. JSON object names must be
    /// strings, so a YAML complex key (a sequence or mapping used as a key) has no
    /// JSON form. PureYAML core already ships ``mappingKeysAreUnique``; this check and
    /// ``numbersAreFinite`` complete the JSON-representability set.
    static var mappingKeysAreStrings: PureYAML.Validation.Validation<PureYAML.Model.Mapping, PureYAML.Model.Value> {
        PureYAML.Validation.Validation(description: "Mapping keys are strings") { context in
            context.subject.pairs.compactMap { pair in
                guard pair.keyNode.stringValue == nil else {
                    return nil
                }
                return PureYAML.Validation.ValidationError(
                    severity: .error,
                    reason: "Mapping key '\(pair.keyNode.description)' is not a string",
                    path: context.path.appending(.complexKey(pair.keyNode)),
                )
            }
        }
    }

    /// Reports any non-finite number (NaN or infinity). JSON has no literal for
    /// these, so a value tree carrying one is not representable as JSON.
    static var numbersAreFinite: PureYAML.Validation.Validation<PureYAML.Model.Value, PureYAML.Model.Value> {
        PureYAML.Validation.Validation(description: "Numbers are finite") { context in
            guard case let .double(number) = context.subject, !number.isFinite else {
                return []
            }
            return [
                PureYAML.Validation.ValidationError(
                    severity: .error,
                    reason: "Number '\(number)' is not finite",
                    path: context.path,
                ),
            ]
        } when: { context in
            if case .double = context.subject {
                return true
            }
            return false
        }
    }
}