Additional value mapping (Hanami 2 integration)

[swilgosz]

Overview

Tweaks for Hanami 2 integration.

Background

During configuring of Hanami 2 project to work with RES-ROM in order to integrate ecommerce application RailsEventStore/ecommerce#110, I have encountered Sequel problem: sequel-error.txt. Command below accepts named arguments, so there is no way to call the command handler directly passing invalid parameters to it.

cmd = Crm::RegisterCustomer.new(customer_id: customer_id, name: name)
command_bus.(cmd)

However, calling command bus with this command returns an Sequel Error: Column not found (details below).

I have found that CreateEvents changeset receives Hash as a value for JSONB columns (data and metadata) in case of Hanami 2 integration, and String in Rails or tests.

To solve it, I added two additional MAP_VALUE rules.

module RubyEventStore
  module ROM
    module Changesets
      class CreateEvents < ::ROM::Changeset::Create
        relation :events

        map(&:to_h)
        map do
          # ...
          map_value   :data, ->(value) { value.class.name == "Hash" ? value.to_json : value }
          map_value   :metadata, ->(value) { value.class.name == "Hash" ? value.to_json : value }
          # ...
        end

        def commit
          relation.multi_insert(to_a)
        end
      end
    end
  end
end

It sems to solve the problem, but I am not happy with this as I believe, I did not find the source of the problem. I expect that some kind of value transformation was not triggered.

Additional notes

1. I've noticed, that active support is only required in tests, so I moved it to the test group.
2. Sequel Error logs: sequel-error.txt

Summary

I keep this PR as a monkey patch for now, until the proper fix is found, to make Hanami 2 integration possible. Help welcome!

[mostlyobvious]

Gemfile is purely for test. We're not using bundler groups at all anywhere in the RES codebase.

You can have a look on ROM dependencies at:

rails_event_store/contrib/ruby_event_store-rom/ruby_event_store-rom.gemspec

Lines 29 to 36 in be89cf8

	spec.add_dependency "dry-container", ">= 0.6"
	spec.add_dependency "dry-initializer", ">= 3.0"
	spec.add_dependency "dry-types", ">= 1.0"
	spec.add_dependency "rom-changeset", ">= 5.0"
	spec.add_dependency "rom-repository", ">= 5.0"
	spec.add_dependency "rom-sql", ">= 3.0"
	spec.add_dependency "sequel", ">= 5.11.0"
	spec.add_dependency "ruby_event_store", ">= 2.0.0", "< 3.0.0"

[mostlyobvious]

Perhaps worth adding a test recreating the situation you've encountered?

[mostlyobvious]

Long story short:

• in RES we do not insist on one particular data/metadata column type — it can be binary (for YAML and Protobuf), json or jsonb
• this column type choice can decided on initial migration
• database engine must support this choice (i.e. default binary works on all: sqlite, mysql, postgres)
• AR repository is checked against all datatypes where RDBMS permits: https://github.com/RailsEventStore/rails_event_store/blob/master/.github/workflows/rails_event_store_active_record.yml#L86-L100
• each choice needs to backed by a serializer that transforms event payload into something appropriate for the column type in storage
• by default each data/metadata payload is turned into string (works well for binary columns)
• json/jsonb columns, when accessed via AR, need something different — Ruby hashes Unexpected behavior when using JSON/JSONB data type with JSON serializer  #651 and in order to provide them a NULL serializer is used
• ROM adapter tests are parametrized against data types too: https://github.com/RailsEventStore/rails_event_store/blob/master/.github/workflows/ruby_event_store-rom.yml#L72-L86 and we seem to explicitly pass JSON serializer there in tests (turning hashes into strings), could be that Sequel behaviour is different than ActiveRecord's one and the advice we give in docs would not apply

[mostlyobvious]

Can you first check that switching https://github.com/RailsEventStore/ecommerce/blob/6de6008878decfb4332a01e052202fb4a473bb4f/hanami_application/config/providers/event_repository.rb#L9 ::RubyEventStore::NULL to ::JSON works as expected?

[mostlyobvious]

Loudly thinking — if there's a way to pass ActiveRecord data/metadata as strings for json/jsonb columns, that do not get additional to-string serialization, that would greatly reduce complexity around serailizers for JSON across all known repositories. Same interface for all (as initially designed) — repository gets serialized-data-as-string and has to put it in right place, without insisting on serializing it once again (as AR does here).

[mostlyobvious]

Btw. that SQL payload was the most valuable part of the exception as it shows data in raw shape as we insert it. Too bad it was trimmed.

Sequel::DatabaseError: PG::UndefinedColumn: ERROR:  column "customer_id" does not exist
LINE 1: ...VALUES ('d20c4621-3874-45d3-8a06-338dc6c969d8', (("customer_...

[mostlyobvious]

Verified: RailsEventStore/ecommerce#110 (comment)