Handle parse errors

CHANGELOG.md

@@ -4,6 +4,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+### Added
+- `INVALID_BODY_FORMAT` JSON:API error
+
+### Changed
+- Rescue and translate `MultiJson::ParseError` while parsing body
+
 ## [2.1.0] - 2020-04-01
 ### Added
 - Headers validation

README.md

@@ -295,6 +295,7 @@ with one issue per line.
 | `:code`                   | `:status` | What is it? |
 |:--------------------------|:----------|:------------|
 | INVALID_RESOURCE_SCHEMA   | 422       | Resource did not pass configured validation |
+| INVALID_BODY_FORMAT       | 400       | Request body is invalid JSON |
 | INVALID_QUERY_PARAMETER   | 400       | Query parameter violates syntax or did not pass configured validation |
 | MISSING_QUERY_PARAMETER   | 400       | Query parameter required in configuration is missing |
 | INVALID_JSON_API          | 400       | Request body violates JSON:API syntax |

lib/request_handler/body_parser.rb

@@ -30,6 +30,10 @@ def request_body
       b.rewind
       b = b.read
       b.empty? ? {} : MultiJson.load(b)
+    rescue MultiJson::ParseError => e
+      raise BodyFormatError, [{ status: '400',
+                                code: 'INVALID_BODY_FORMAT',
+                                detail: e.message }]
     end
 
     attr_reader :request, :schema, :schema_options, :type

lib/request_handler/error.rb

@@ -42,6 +42,8 @@ class OptionNotAllowedError < JsonApiError
   class NoConfigAvailableError < InternalBaseError
   end
 
+  class BodyFormatError < ExternalArgumentError
+  end
   class BodyParamsError < ExternalArgumentError
   end
   class FieldsetsParamsError < ExternalArgumentError

spec/request_handler/body_parser_spec.rb

@@ -103,6 +103,20 @@
         .to raise_error(RequestHandler::MissingArgumentError)
     end
 
+    it 'fails if the request body is not json' do
+      schema = Dry::Schema.JSON {}
+      expect do
+        described_class.new(
+          schema: schema,
+          type: type,
+          request: instance_double('Rack::Request',
+                                   params: {},
+                                   body: StringIO.new('foo'))
+        ).run
+      end
+        .to raise_error(RequestHandler::BodyFormatError)
+    end
+
     it "doesn't fail if the request body does not contain a data hash" do
       schema = Dry::Schema.JSON {}
       expect do