Only allow defined formats.

We've been accidentally using invalid formats like "timestamp" in some places, so this helps ensure we use formats that will actually have a validation effect.

lib/interpol/endpoint.rb

@@ -21,6 +21,32 @@ def data_valid_for_type?(data, type)
       end
     end
   end
+
+  # Monkey patch json-schema to only allow the defined formats.
+  # We've been accidentally using invalid formats like "timestamp",
+  # so this will help ensure we only use valid ones.
+  class Validator
+    VALID_FORMATS = %w[
+      date-time date time utc-millisec regex color style
+      phone uri email ip-address ipv6 host-name
+    ]
+
+    def open(uri)
+      return super unless uri.start_with?('file://') && uri.end_with?('draft-03.json')
+      return StringIO.new(Validator.overriden_draft_03) if Validator.overriden_draft_03
+
+      schema = JSON.parse(super.read)
+      schema.fetch("properties").fetch("format")["enum"] = VALID_FORMATS
+
+      override = JSON.dump(schema)
+      Validator.overriden_draft_03 = override
+      StringIO.new(override)
+    end
+
+    class << self
+      attr_accessor :overriden_draft_03
+    end
+  end
 end
 
 module Interpol

spec/unit/interpol/endpoint_spec.rb

@@ -323,6 +323,26 @@ def new_with(hash)
         }.to raise_error(ValidationError)
       end
 
+      let(:date_time_string) { "2012-12-12T08:23:12Z" }
+
+      it 'rejects unrecognized format options' do
+        schema['properties']['foo']['type'] = 'string'
+        schema['properties']['foo']['format'] = 'timestamp' # the valid format is date-time
+
+        expect {
+          subject.validate_data!('foo' => date_time_string)
+        }.to raise_error(ValidationError, %r|'#/properties/foo/format' value "timestamp"|)
+      end
+
+      it 'allows recognized format options' do
+        schema['properties']['foo']['type'] = 'string'
+        schema['properties']['foo']['format'] = 'date-time'
+
+        expect {
+          subject.validate_data!('foo' => date_time_string)
+        }.not_to raise_error
+      end
+
       it 'requires all properties' do
         expect {
           subject.validate_data!({})