GraphQL::Plugin::Convert::DBIC - convert DBIx::Class schema to GraphQL schema

OS	Build status
Linux

use GraphQL::Plugin::Convert::DBIC;
use Schema;
my $converted = GraphQL::Plugin::Convert::DBIC->to_graphql(
  sub { Schema->connect }
);
print $converted->{schema}->to_doc;

This module implements the GraphQL::Plugin::Convert API to convert a DBIx::Class::Schema to GraphQL::Schema etc.

Its Query type represents a guess at what fields are suitable, based on providing a lookup for each type (a DBIx::Class::ResultSource).

Consider this minimal data model:

blog:
  id # primary key
  articles # has_many
  title # non null
  language # nullable
article:
  id # primary key
  blog # foreign key to Blog
  title # non null
  content # nullable

These GraphQL::Type::Object types will be generated:

type Blog {
  id: Int!
  articles: [Article]
  title: String!
  language: String
}

type Article {
  id: Int!
  blog: Blog
  title: String!
  content: String
}

type Query {
  blog(id: [Int!]!): [Blog]
  article(id: [Int!]!): [Blog]
}

Note that while the queries take a list, the return order is undefined. This also applies to the mutations. If this matters, request the primary key fields and use those to sort.

Different input types are needed for each of CRUD (Create, Read, Update, Delete).

The create one needs to have non-null fields be non-null, for idiomatic GraphQL-level error-catching. The read one needs all fields nullable, since this will be how searches are implemented, allowing fields to be left un-searched-for. Both need to omit primary key fields. The read one also needs to omit foreign key fields, since the idiomatic GraphQL way for this is to request the other object, with this as a field on it, then request any required fields of this.

Meanwhile, the update and delete ones need to include the primary key fields, to indicate what to mutate, and also all non-primary key fields as nullable, which for update will mean leaving them unchanged, and for delete is to be ignored.

Therefore, for the above, these input types (and an updated Query, and Mutation) are created:

input BlogCreateInput {
  title: String!
  language: String
}

input BlogSearchInput {
  title: String
  language: String
}

input BlogMutateInput {
  id: Int!
  title: String
  language: String
}

input ArticleCreateInput {
  blog_id: Int!
  title: String!
  content: String
}

input ArticleSearchInput {
  title: String
  content: String
}

input ArticleMutateInput {
  id: Int!
  title: String!
  language: String
}

type Mutation {
  createBlog(input: [BlogCreateInput!]!): [Blog]
  createArticle(input: [ArticleCreateInput!]!): [Article]
  deleteBlog(input: [BlogMutateInput!]!): [Boolean]
  deleteArticle(input: [ArticleMutateInput!]!): [Boolean]
  updateBlog(input: [BlogMutateInput!]!): [Blog]
  updateArticle(input: [ArticleMutateInput!]!): [Article]
}

extends type Query {
  searchBlog(input: BlogSearchInput!): [Blog]
  searchArticle(input: ArticleSearchInput!): [Article]
}

To the to_graphql method: a code-ref returning a DBIx::Class::Schema object. This is so it can be called during the conversion process, but also during execution of a long-running process to e.g. execute database queries, when the database handle passed to this method as a simple value might have expired.

This is available as \&GraphQL::Plugin::Convert::DBIC::field_resolver in case it is wanted for use outside of the "bundle" of the to_graphql method.

To debug, set environment variable GRAPHQL_DEBUG to a true value.

Ed J, <etj at cpan.org>

Copyright (C) Ed J

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.