add validator for discriminator value property

Author: jenschude

ctp-validators/src/main/kotlin/com/commercetools/rmf/validators/DiscriminatorValueRule.kt

@@ -0,0 +1,36 @@
+package com.commercetools.rmf.validators
+
+import io.vrap.rmf.raml.model.types.BuiltinType
+import io.vrap.rmf.raml.model.types.ObjectType
+import org.eclipse.emf.common.util.Diagnostic
+import java.util.*
+
+@ValidatorSet
+class DiscriminatorValueRule(severity: RuleSeverity, options: List<RuleOption>? = null) : TypesRule(severity, options) {
+
+    private val exclude: List<String> =
+        (options?.filter { ruleOption -> ruleOption.type.lowercase(Locale.getDefault()) == RuleOptionType.EXCLUDE.toString() }?.map { ruleOption -> ruleOption.value }?.plus("") ?: defaultExcludes)
+
+    override fun caseObjectType(type: ObjectType): List<Diagnostic> {
+        val validationResults: MutableList<Diagnostic> = ArrayList()
+
+        if (type.discriminator != null && type.discriminatorValue != null && !type.isInlineType && exclude.contains(type.name).not()) {
+            validationResults.add(create(type, "Discriminator and DiscriminatorValue property defined in the same type: {0}", type.name))
+        }
+
+        return validationResults
+    }
+
+    companion object : ValidatorFactory<DiscriminatorValueRule> {
+        private val defaultExcludes by lazy { listOf("") }
+
+        @JvmStatic
+        override fun create(options: List<RuleOption>?): DiscriminatorValueRule {
+            return DiscriminatorValueRule(RuleSeverity.ERROR, options)
+        }
+
+        @JvmStatic
+        override fun create(severity: RuleSeverity, options: List<RuleOption>?): DiscriminatorValueRule {
+            return DiscriminatorValueRule(severity, options)
+        }    }
+}