Support overriding the table alias name

Continue #18

When the association scope is chained with conditions of other tables, the names of join tables are also added to `references_values`. It becomes impossible to identify the table alias name from the `references_values`.

The PR provides a way to customize the table alias name when the default way cannot figure out the correct value.

Author: Arthur Chui

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    jit_preloader (0.2.3)
+    jit_preloader (0.2.5)
       activerecord (> 4.2, < 6)
       activesupport
 
@@ -63,4 +63,4 @@ DEPENDENCIES
   sqlite3
 
 BUNDLED WITH
-   2.0.1
+   2.1.4

lib/jit_preloader/active_record/base.rb

@@ -55,7 +55,7 @@ def self.prepended(base)
     class << base
       delegate :jit_preload, to: :all
 
-      def has_many_aggregate(assoc, name, aggregate, field, default: 0)
+      def has_many_aggregate(assoc, name, aggregate, field, table_alias_name: nil, default: 0)
         method_name = "#{assoc}_#{name}"
 
         define_method(method_name) do |conditions={}|
@@ -77,24 +77,23 @@ def has_many_aggregate(assoc, name, aggregate, field, default: 0)
             association_scope = association_scope.instance_exec(&reflection.scope).reorder(nil) if reflection.scope
 
             # If the query uses an alias for the association, use that instead of the table name
-            table_alias_name = association_scope.references_values.first
-            table_reference = table_alias_name || aggregate_association.table_name
+            table_alias_name ||= association_scope.references_values.first || aggregate_association.table_name
 
-            conditions[table_reference] = { aggregate_association.foreign_key => primary_ids }
+            conditions[table_alias_name] = { aggregate_association.foreign_key => primary_ids }
 
             # If the association is a STI child model, specify its type in the condition so that it
             # doesn't include results from other child models
             parent_is_base_class = aggregate_association.klass.superclass.abstract_class? || aggregate_association.klass.superclass == ActiveRecord::Base
             has_type_column = aggregate_association.klass.column_names.include?(aggregate_association.klass.inheritance_column)
             is_child_sti_model = !parent_is_base_class && has_type_column
             if is_child_sti_model
-              conditions[table_reference].merge!({ aggregate_association.klass.inheritance_column => aggregate_association.klass.sti_name })
+              conditions[table_alias_name].merge!({ aggregate_association.klass.inheritance_column => aggregate_association.klass.sti_name })
             end
 
             if reflection.type.present?
               conditions[reflection.type] = self.class.name
             end
-            group_by = "#{table_reference}.#{aggregate_association.foreign_key}"
+            group_by = "#{table_alias_name}.#{aggregate_association.foreign_key}"
 
             preloaded_data = Hash[association_scope
               .where(conditions)

lib/jit_preloader/version.rb

@@ -1,3 +1,3 @@
 module JitPreloader
-  VERSION = "0.2.4"
+  VERSION = "0.2.5"
 end

spec/lib/jit_preloader/preloader_spec.rb

@@ -106,6 +106,19 @@
         expect(contact_books.first.children).to include(child1, child2, child3)
       end
     end
+
+    context "when preloading an aggregate for a child model scoped by another join table" do
+      let!(:contact_book) { ContactBook.create(name: "The Yellow Pages") }
+      let!(:contact1) { Company.create(name: "Without Email", contact_book: contact_book) }
+      let!(:contact2) { Company.create(name: "With Blank Email", email_address: EmailAddress.new(address: ""), contact_book: contact_book) }
+      let!(:contact3) { Company.create(name: "With Email", email_address: EmailAddress.new(address: "[email protected]"), contact_book: contact_book) }
+
+      it "can handle queries" do
+        contact_books = ContactBook.jit_preload.to_a
+        expect(contact_books.first.companies_with_blank_email_address_count).to eq 1
+        expect(contact_books.first.companies_with_blank_email_address).to eq [contact2]
+      end
+    end
   end
 
   context "when preloading an aggregate as polymorphic" do

spec/support/models.rb

@@ -12,6 +12,9 @@ class ContactBook < ActiveRecord::Base
   has_many_aggregate :employees, :count, :count, "*"
   has_many_aggregate :company_employees, :count, :count, "*"
   has_many_aggregate :children, :count, :count, "*"
+
+  has_many :companies_with_blank_email_address, -> { joins(:email_address).where(email_addresses: { address: "" }) }, class_name: "Company"
+  has_many_aggregate :companies_with_blank_email_address, :count, :count, "*", table_alias_name: "contacts"
 end
 
 class Contact < ActiveRecord::Base