feat: use 2020-12 as default schema

BREAKING CHANGE: JSON Schema 2020-12 is used by default

Author: kylef

CHANGELOG.md

@@ -4,6 +4,10 @@
 
 ### Breaking Changes
 
+- By default, the _latest_ version of JSON Schema will be used when a meta
+  schema is not provided in the `$schema` property. The default schema will be
+  2020-12 for this release.
+
 - When a schema references an unknown meta schema via `$schema`, a reference
   error will now be thrown instead of the schema being silently treated as a
   draft 4 schema.

Sources/JSONSchema.swift

@@ -66,7 +66,7 @@ public struct Schema {
 func validator(for schema: [String: Any]) throws -> Validator {
   guard schema.keys.contains("$schema") else {
     // Default schema
-    return Draft4Validator(schema: schema)
+    return Draft202012Validator(schema: schema)
   }
 
   guard let schemaURI = schema["$schema"] as? String else {

Tests/JSONSchemaTests/JSONSchemaCases.swift

@@ -17,7 +17,7 @@ func draft4Validator(schema: Any, instance: Any) throws -> ValidationResult {
   }
 
   if let schema = schema as? [String: Any] {
-    return try validate(instance, schema: schema)
+    return try Draft4Validator(schema: schema).validate(instance: instance)
   }
 
   fatalError()

Tests/JSONSchemaTests/JSONSchemaTests.swift

@@ -110,7 +110,7 @@ class ValidateTests: XCTestCase {
 
   func testDefaultValidator() throws {
     let result = try validator(for: [:])
-    XCTAssertTrue(result is Draft4Validator, "Unexpected type of validator \(result)")
+    XCTAssertTrue(result is Draft202012Validator, "Unexpected type of validator \(result)")
   }
 
   func testDraft4ValidatorIsAvailable() throws {