Allow to disable rules compressor (#798)

Author: coorasse

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 * [#653](https://github.com/CanCanCommunity/cancancan/pull/653): Add support for using an nil relation as a condition. ([@ghiculescu][])
 * [#702](https://github.com/CanCanCommunity/cancancan/pull/702): Support scopes of STI classes as ability conditions. ([@honigc][])
+* [#798](https://github.com/CanCanCommunity/cancancan/pull/798): Allow disabling of rules compressor via `CanCan.rules_compressor_enabled = false`. ([@coorasse][])
 
 ## 3.4.0
 

docs/rules_compression.md

@@ -1,6 +1,12 @@
 # Rules compressions
 
-Your rules are optimized automatically at runtime. There are a set of "rules" to optimize your rules definition and they are implemented in the `RulesCompressor` class. Here you can see how this works:
+Database are great on optimizing queries, but sometimes cancancan builds `joins` that might lead to slow performance.
+This is why your rules are optimized automatically at runtime.
+There are a set of "rules" to optimize your rules definition and they are implemented in the `RulesCompressor` class.
+You can always disable the rules compressor by setting `CanCan.rules_compressor_enabled = false` in your initializer.
+You can also enable/disable it on a specific check by using: `with_rules_compressor_enabled(false) { ... }`
+
+Here you can see how this works:
 
 A rule without conditions is defined as `catch_all`.
 

lib/cancan/config.rb

@@ -11,6 +11,29 @@ def self.valid_accessible_by_strategies
     strategies
   end
 
+  # You can disable the rules compressor if it's causing unexpected issues.
+  def self.rules_compressor_enabled
+    return @rules_compressor_enabled if defined?(@rules_compressor_enabled)
+
+    @rules_compressor_enabled = true
+  end
+
+  def self.rules_compressor_enabled=(value)
+    @rules_compressor_enabled = value
+  end
+
+  def self.with_rules_compressor_enabled(value)
+    return yield if value == rules_compressor_enabled
+
+    begin
+      rules_compressor_enabled_was = rules_compressor_enabled
+      @rules_compressor_enabled = value
+      yield
+    ensure
+      @rules_compressor_enabled = rules_compressor_enabled_was
+    end
+  end
+
   # Determines how CanCan should build queries when calling accessible_by,
   # if the query will contain a join. The default strategy is `:subquery`.
   #

lib/cancan/model_adapters/active_record_adapter.rb

@@ -15,7 +15,11 @@ def self.version_lower?(version)
 
       def initialize(model_class, rules)
         super
-        @compressed_rules = RulesCompressor.new(@rules.reverse).rules_collapsed.reverse
+        @compressed_rules = if CanCan.rules_compressor_enabled
+                              RulesCompressor.new(@rules.reverse).rules_collapsed.reverse
+                            else
+                              @rules
+                            end
         StiNormalizer.normalize(@compressed_rules)
         ConditionsNormalizer.normalize(model_class, @compressed_rules)
       end
@@ -39,8 +43,8 @@ def nested_subject_matches_conditions?(parent, child, all_conditions)
         def parent_child_conditions(parent, child, all_conditions)
           child_class = child.is_a?(Class) ? child : child.class
           foreign_key = child_class.reflect_on_all_associations(:belongs_to).find do |association|
-                          association.klass == parent.class
-                        end&.foreign_key&.to_sym
+            association.klass == parent.class
+          end&.foreign_key&.to_sym
           foreign_key.nil? ? nil : all_conditions[foreign_key]
         end
       end

spec/cancan/model_adapters/active_record_adapter_spec.rb

@@ -393,12 +393,26 @@ class User < ActiveRecord::Base
         expect(@ability.model_adapter(Article, :read).joins).to be_nil
       end
 
-      it 'has nil joins if rules got compressed' do
-        @ability.can :read, Comment, article: { category: { visible: true } }
-        @ability.can :read, Comment
-        expect(@ability.model_adapter(Comment, :read))
-          .to generate_sql("SELECT \"#{@comment_table}\".* FROM \"#{@comment_table}\"")
-        expect(@ability.model_adapter(Comment, :read).joins).to be_nil
+      context 'if rules got compressed' do
+        it 'has nil joins' do
+          @ability.can :read, Comment, article: { category: { visible: true } }
+          @ability.can :read, Comment
+          expect(@ability.model_adapter(Comment, :read))
+            .to generate_sql("SELECT \"#{@comment_table}\".* FROM \"#{@comment_table}\"")
+          expect(@ability.model_adapter(Comment, :read).joins).to be_nil
+        end
+      end
+
+      context 'if rules did not get compressed' do
+        before :each do
+          CanCan.rules_compressor_enabled = false
+        end
+
+        it 'has joins' do
+          @ability.can :read, Comment, article: { category: { visible: true } }
+          @ability.can :read, Comment
+          expect(@ability.model_adapter(Comment, :read).joins).to be_present
+        end
       end
 
       it 'has nil joins if no nested hashes specified in conditions' do

spec/spec_helper.rb

@@ -30,6 +30,7 @@
 
   config.after :each do
     CanCan.accessible_by_strategy = CanCan.default_accessible_by_strategy
+    CanCan.rules_compressor_enabled = true
   end
 end