Allow lazy loading associations

Closes #215

spec/lazy_loading_spec.cr

@@ -0,0 +1,37 @@
+require "./spec_helper"
+
+include LazyLoadHelpers
+
+describe "Lazy loading associations" do
+  it "can lazy load has_many and has_many through" do
+    post = PostBox.save
+    comment = CommentBox.new.post_id(post.id).save
+    tag = TagBox.save
+    tagging = TaggingBox.new.post_id(post.id).tag_id(tag.id).save
+
+    post.comments!.should eq([comment])
+    post.tags!.should eq([tag])
+  end
+
+  it "can lazy load has_one" do
+    admin = AdminBox.save
+    sign_in_credential = SignInCredentialBox.new.user_id(admin.id).save
+    admin.sign_in_credential!.should eq(sign_in_credential)
+  end
+
+  it "can lazy load optional has_one" do
+    user = UserBox.save
+    user.sign_in_credential!.should be_nil
+  end
+
+  it "can lazy load belongs_to" do
+    post = PostBox.save
+    comment = CommentBox.new.post_id(post.id).save
+    comment.post!.should eq(post)
+  end
+
+  it "can lazy load optional belongs_to" do
+    employee = EmployeeBox.save
+    employee.manager!.should be_nil
+  end
+end

spec/preloading_spec.cr

@@ -1,5 +1,7 @@
 require "./spec_helper"
 
+include LazyLoadHelpers
+
 describe "Preloading" do
   it "can disable lazy loading" do
     with_lazy_load(enabled: false) do
@@ -162,17 +164,3 @@ describe "Preloading" do
     posts.results.first.comments.should eq([comment])
   end
 end
-
-private def with_lazy_load(enabled)
-  begin
-    LuckyRecord::Repo.configure do
-      settings.lazy_load_enabled = enabled
-    end
-
-    yield
-  ensure
-    LuckyRecord::Repo.configure do
-      settings.lazy_load_enabled = true
-    end
-  end
-end

spec/support/lazy_load_helpers.cr

@@ -0,0 +1,15 @@
+module LazyLoadHelpers
+  private def with_lazy_load(enabled)
+    begin
+      LuckyRecord::Repo.configure do
+        settings.lazy_load_enabled = enabled
+      end
+
+      yield
+    ensure
+      LuckyRecord::Repo.configure do
+        settings.lazy_load_enabled = true
+      end
+    end
+  end
+end

src/lucky_record/associations.cr

@@ -24,30 +24,38 @@ module LuckyRecord::Associations
 
     def {{ assoc_name.id }} : Array({{ model }})
       @_preloaded_{{ assoc_name }} \
-      || lazy_load_{{ assoc_name }} \
+      || maybe_lazy_load_{{ assoc_name }} \
       || raise LuckyRecord::LazyLoadError.new {{ @type.name.stringify }}, {{ assoc_name.stringify }}
     end
 
-    private def lazy_load_{{ assoc_name }} : Array({{ model }})?
+    def {{ assoc_name.id }}! : Array({{ model }})
+      @_preloaded_{{ assoc_name }} || lazy_load_{{ assoc_name }}
+    end
+
+    private def maybe_lazy_load_{{ assoc_name }}  : Array({{ model }})?
       if lazy_load_enabled?
-        {% if through %}
-          {{ model }}::BaseQuery
-            .new
-            .join_{{ through.id }}
-            .{{ through.id }} do |through_query|
-              through_query.{{ foreign_key.id }}(id)
-            end
-            .preload_{{ through.id }}
-            .results
-        {% else %}
-          {{ model }}::BaseQuery
-            .new
-            .{{ foreign_key }}(id)
-            .results
-        {% end %}
+        lazy_load_{{ assoc_name }}
       end
     end
 
+    private def lazy_load_{{ assoc_name }} : Array({{ model }})
+      {% if through %}
+        {{ model }}::BaseQuery
+          .new
+          .join_{{ through.id }}
+          .{{ through.id }} do |through_query|
+            through_query.{{ foreign_key.id }}(id)
+          end
+          .preload_{{ through.id }}
+          .results
+      {% else %}
+        {{ model }}::BaseQuery
+          .new
+          .{{ foreign_key }}(id)
+          .results
+      {% end %}
+    end
+
     class BaseQuery < LuckyRecord::Query
       def preload_{{ assoc_name }}
         preload({{ model }}::BaseQuery.new)
@@ -113,10 +121,18 @@ module LuckyRecord::Associations
       @_preloaded_{{ assoc_name }} = record
     end
 
+    def {{ assoc_name.id }}! : {{ model }}{% if nilable %}?{% end %}
+      get_{{ assoc_name.id }}(allow_lazy: true)
+    end
+
     def {{ assoc_name.id }} : {{ model }}{% if nilable %}?{% end %}
+      get_{{ assoc_name.id }}
+    end
+
+    private def get_{{ assoc_name.id }}(allow_lazy : Bool = false) : {{ model }}{% if nilable %}?{% end %}
       if _{{ assoc_name }}_preloaded?
         @_preloaded_{{ assoc_name }}{% unless nilable %}.not_nil!{% end %}
-      elsif lazy_load_enabled?
+      elsif lazy_load_enabled? || allow_lazy
         query = {{ model }}::BaseQuery.new
         query.{{ foreign_key.id }}(id)
 
@@ -160,10 +176,18 @@ module LuckyRecord::Associations
 
     association table_name: :{{ model.resolve.constant(:TABLE_NAME).id }}, type: {{ model }}, foreign_key: :id
 
+    def {{ assoc_name.id }}! : {{ model }}{% if nilable %}?{% end %}
+      get_{{ assoc_name.id }}(allow_lazy: true)
+    end
+
     def {{ assoc_name.id }} : {{ model }}{% if nilable %}?{% end %}
+      get_{{ assoc_name.id }}
+    end
+
+    private def get_{{ assoc_name.id }}(allow_lazy : Bool = false) : {{ model }}{% if nilable %}?{% end %}
       if _{{ assoc_name }}_preloaded?
         @_preloaded_{{ assoc_name }}{% unless nilable %}.not_nil!{% end %}
-      elsif lazy_load_enabled?
+      elsif lazy_load_enabled? || allow_lazy
         {{ foreign_key }}.try do |value|
           {{ model }}::BaseQuery.new.find(value)
         end