Don't autocorrect BigDecimal with float when precision is specified

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug fixes
 
 * [#147](https://github.com/rubocop-hq/rubocop-performance/issues/147): Fix an error for `Performance/AncestorsInclude` when using `ancestors.include?` without receiver. ([@koic][])
+* [#150](https://github.com/rubocop-hq/rubocop-performance/pull/150): Fix an incorrect autocorrect for `Performance/BigDecimalWithNumericArgument` when a precision is specified. ([@eugeneius][])
 
 ### Changes
 

lib/rubocop/cop/performance/big_decimal_with_numeric_argument.rb

@@ -25,6 +25,8 @@ class BigDecimalWithNumericArgument < Cop
 
         def on_send(node)
           big_decimal_with_numeric_argument?(node) do |numeric|
+            next if numeric.float_type? && specifies_precision?(node)
+
             add_offense(node, location: numeric.source_range)
           end
         end
@@ -36,6 +38,12 @@ def autocorrect(node)
             end
           end
         end
+
+        private
+
+        def specifies_precision?(node)
+          node.arguments.size > 1 && !node.arguments[1].hash_type?
+        end
       end
     end
   end

spec/rubocop/cop/performance/big_decimal_with_numeric_argument_spec.rb

@@ -16,12 +16,31 @@
 
   it 'registers an offense and corrects when using `BigDecimal` with float' do
     expect_offense(<<~RUBY)
-      BigDecimal(1.5, 2, exception: true)
+      BigDecimal(1.5, exception: true)
                  ^^^ Convert numeric argument to string before passing to `BigDecimal`.
     RUBY
 
     expect_correction(<<~RUBY)
-      BigDecimal('1.5', 2, exception: true)
+      BigDecimal('1.5', exception: true)
+    RUBY
+  end
+
+  it 'does not register an offense when using `BigDecimal` with float and precision' do
+    expect_no_offenses(<<~RUBY)
+      BigDecimal(3.14, 1)
+    RUBY
+  end
+
+  it 'does not register an offense when using `BigDecimal` with float and non-literal precision' do
+    expect_no_offenses(<<~RUBY)
+      precision = 1
+      BigDecimal(3.14, precision)
+    RUBY
+  end
+
+  it 'does not register an offense when using `BigDecimal` with float, precision, and a keyword argument' do
+    expect_no_offenses(<<~RUBY)
+      BigDecimal(3.14, 1, exception: true)
     RUBY
   end