feat: add PG::JSONB converter

Closes #81

Author: vladfaust

db_spec/pg/migration.sql

@@ -34,6 +34,7 @@ CREATE TABLE posts(
   editor_uuid UUID                  REFERENCES users (uuid),
   tag_ids     INT[],
   content     TEXT        NOT NULL,
+  meta        JSONB       NOT NULL  DEFAULT '{}',
   created_at  TIMESTAMPTZ NOT NULL  DEFAULT NOW(),
   updated_at  TIMESTAMPTZ
 );

db_spec/pg/models.cr

@@ -1,6 +1,7 @@
 require "../../src/onyx-sql/converters/pg"
 require "../../src/onyx-sql/converters/pg/uuid"
 require "../../src/onyx-sql/converters/pg/json"
+require "../../src/onyx-sql/converters/pg/jsonb"
 
 alias Model = Onyx::SQL::Model
 alias Field = Onyx::SQL::Field
@@ -60,10 +61,15 @@ end
 class Post
   include Model
 
+  record Meta, meta : Hash(String, String) do
+    include JSON::Serializable
+  end
+
   schema posts do
     pkey id : Int32, converter: PG::Any(Int32)
 
     type content : String, not_null: true
+    type meta : Meta, converter: PG::JSONB(Meta)
     type created_at : Time, default: true, not_null: true
     type updated_at : Time
 

db_spec/pg/repository/query_spec.cr

@@ -101,12 +101,13 @@ describe "Repository(Postgres)#query" do
   describe "insert" do
     context "with complex model" do
       post = repo.query(Post.query
-        .insert(author: user, tags: [tag], content: "Blah-blah")
+        .insert(author: user, tags: [tag], content: "Blah-blah", meta: Post::Meta.new({"foo" => "bar"}))
         .returning(Post)
       ).first
 
       it "returns model instance" do
         post.should be_a(Post)
+        post.meta!.meta.should eq({"foo" => "bar"})
       end
 
       it "preloads direct non-enumerable references" do

src/onyx-sql/converters/pg/json.cr

@@ -2,8 +2,8 @@ require "../pg"
 require "../../ext/pg/result_set"
 require "json"
 
-# Converts between the PostgreSQL's native `JSON` and `JSONB` types and Crystal objects with
-# `#to_json` and `.from_json` methods (e.g. `JSON::Serializable`).
+# Converts between the PostgreSQL's native `"JSON"` column type and Crystal objects with
+# `#to_json` and `.from_json` methods (e.g. `JSON::Serializable` or `Hash`).
 # See `Field` to read about of how to apply converters.
 #
 # ```sql
@@ -33,7 +33,7 @@ module Onyx::SQL::Converters::PG::JSON(T)
     value.to_json
   end
 
-  def self.from_rs(rs : DB::ResultSet)
+  def self.from_rs(rs : DB::ResultSet) : T?
     bytes = rs.read_raw
     bytes.try do |bytes|
       T.from_json(String.new(bytes))

src/onyx-sql/converters/pg/jsonb.cr

@@ -0,0 +1,24 @@
+require "../pg"
+require "../../ext/pg/result_set"
+require "json"
+
+# Converts between the PostgreSQL's `"JSONB"` type and Crystal objects.
+# It works the same way as the `JSON` converter does, but with `"JSONB"` type.
+#
+# OPTIMIZE: Refactor to extend the `JSON` module. Currently impossible due to https://github.com/crystal-lang/crystal/issues/7167.
+module Onyx::SQL::Converters::PG::JSONB(T)
+  def self.to_db(value : T) : DB::Any
+    value.to_json
+  end
+
+  def self.from_rs(rs : DB::ResultSet) : T?
+    bytes = rs.read_raw
+    bytes.try do |bytes|
+      T.from_json(String.new(bytes[1, bytes.bytesize - 1]))
+    end
+  end
+
+  def self.from_rs_array(rs) : T?
+    from_rs(rs)
+  end
+end