Fix move namespaced constant in Style/ConditionalAssignment

Fix autocorrect for moving constant assignment outside the condition
when the constant is in a namespace, e.g. from:

```ruby
condition ? FOO::BAR = 1 : FOO::BAR = 2

if condition
  ::FOO = 1
else
  ::FOO = 2
end
```

to keep the namespace `Foo::` and the top-level `::` in correction:

```ruby
FOO::BAR = cond? ? 1 : 2

::FOO = if condition
  1
else
  2
end
```

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug fixes
 
 * [#8324](https://github.com/rubocop-hq/rubocop/issues/8324): Fix crash for `Layout/SpaceAroundMethodCallOperator` when using `Proc#call` shorthand syntax. ([@fatkodima][])
+* [#8332](https://github.com/rubocop-hq/rubocop/pull/8332): Fix auto-correct in `Style/ConditionalAssignment` to preserve constant namespace. ([@biinari][])
 
 ## 0.88.0 (2020-07-13)
 

lib/rubocop/cop/style/conditional_assignment.rb

@@ -43,7 +43,7 @@ def lhs(node)
           when :and_asgn, :or_asgn
             "#{node.children[0].source} #{node.loc.operator.source} "
           when :casgn
-            "#{node.children[1]} = "
+            lhs_for_casgn(node)
           when *ConditionalAssignment::VARIABLE_ASSIGNMENT_TYPES
             "#{node.children[0]} = "
           else
@@ -93,6 +93,15 @@ def lhs_for_send(node)
           end
         end
 
+        def lhs_for_casgn(node)
+          namespace = node.children[0]
+          if namespace.nil? || namespace.cbase_type?
+            "#{namespace&.source}#{node.children[1]} = "
+          else
+            "#{namespace.source}::#{node.children[1]} = "
+          end
+        end
+
         def setter_method?(method_name)
           method_name.to_s.end_with?(EQUAL) &&
             !%i[!= == === >= <=].include?(method_name)

spec/rubocop/cop/style/conditional_assignment_assign_to_condition_spec.rb

@@ -1563,6 +1563,44 @@
       end
     end
 
+    context 'constant assignment' do
+      it 'corrects if..else with namespaced constant' do
+        expect_offense(<<~RUBY)
+          if something
+          ^^^^^^^^^^^^ Use the return of the conditional for variable assignment and comparison.
+            FOO::BAR = 1
+          else
+            FOO::BAR = 2
+          end
+        RUBY
+        expect_correction(<<~RUBY)
+          FOO::BAR = if something
+            1
+          else
+            2
+          end
+        RUBY
+      end
+
+      it 'corrects if..else with top-level constant' do
+        expect_offense(<<~RUBY)
+          if something
+          ^^^^^^^^^^^^ Use the return of the conditional for variable assignment and comparison.
+            ::BAR = 1
+          else
+            ::BAR = 2
+          end
+        RUBY
+        expect_correction(<<~RUBY)
+          ::BAR = if something
+            1
+          else
+            2
+          end
+        RUBY
+      end
+    end
+
     context 'self.attribute= assignment' do
       it 'corrects if..else' do
         expect_offense(<<~RUBY)