Add ConfluentSchemaRegistry#compatibility_issues for debugging breaking changes

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Add `compatibility_issues` method to `ConfluentSchemaRegistry` to debug compatibility issues between a schema versions for a given subject (#212)
+
 ## v1.17.0
 
 - Add `register_schemas` option to `encode` method [#210](https://github.com/dasch/avro_turf/pull/210)

README.md

@@ -254,6 +254,9 @@ registry = AvroTurf::ConfluentSchemaRegistry.new("http://my-registry:8081/")
 
 # Returns true if the schema is compatible, nil if the subject or version is not registered, and false if incompatible.
 registry.compatible?("person", schema)
+
+# Returns an array of any breaking changes, nil if the subject or version is not registered
+registry.compatibility_issues("person", schema)
 ```
 
 The ConfluentSchemaRegistry client can also change the global compatibility level or the compatibility level for an individual subject using the [Config API](http://docs.confluent.io/3.1.2/schema-registry/docs/api.html#config):

lib/avro_turf/confluent_schema_registry.rb

@@ -101,6 +101,18 @@ def compatible?(subject, schema, version = 'latest')
     data.fetch('is_compatible', false) unless data.has_key?('error_code')
   end
 
+  # Check for specific schema compatibility issues
+  # Returns:
+  # - nil if the subject or version does not exist
+  # - a list of compatibility issues
+  # https://docs.confluent.io/platform/current/schema-registry/develop/api.html#sr-api-compatibility
+  def compatibility_issues(subject, schema, version = 'latest')
+    data = post("/compatibility/subjects/#{@schema_context_prefix}#{subject}/versions/#{version}",
+      expects: [200, 404], body: { schema: schema.to_s }.to_json, query: { verbose: true }, idempotent: true)
+
+    data.fetch('messages', []) unless data.has_key?('error_code')
+  end
+
   # Get global config
   def global_config
     get("/config", idempotent: true)