Fix to get regexp properly from the pattern constraint (#247)

Author: Kieun

restdocs-api-spec-jsonschema/src/main/kotlin/com/epages/restdocs/apispec/jsonschema/ConstraintResolver.kt

@@ -36,7 +36,7 @@ internal object ConstraintResolver {
 
     private fun FieldDescriptor.maybeSizeConstraint() = findConstraints(this).firstOrNull { SIZE_CONSTRAINT == it.name }
 
-    internal fun maybePattern(fieldDescriptor: FieldDescriptor?) = fieldDescriptor?.maybePatternConstraint()?.let { it.configuration["pattern"] as? String }
+    internal fun maybePattern(fieldDescriptor: FieldDescriptor?) = fieldDescriptor?.maybePatternConstraint()?.let { it.configuration["regexp"] as? String }
 
     private fun FieldDescriptor.maybePatternConstraint() = findConstraints(this).firstOrNull { PATTERN_CONSTRAINT == it.name }
 

restdocs-api-spec-jsonschema/src/test/kotlin/com/epages/restdocs/apispec/jsonschema/JsonSchemaFromFieldDescriptorsGeneratorTest.kt

@@ -650,7 +650,7 @@ class JsonSchemaFromFieldDescriptorsGeneratorTest {
                 listOf(
                     Constraint(
                         "javax.validation.constraints.Pattern",
-                        mapOf("pattern" to "[a-z]")
+                        mapOf("regexp" to "[a-z]")
                     )
                 )
             )