[Fix rubocop#1234] Fix an incorrect autocorrect for Rails/FindBy

Fixes rubocop#1234.

This PR fixes an incorrect autocorrect for `Rails/FindBy`
when using multi-line leading dot method calls.

changelog/fix_an_incorrect_autocorrect_for_rails_find_by.md

@@ -0,0 +1 @@
+* [#1234](https://github.com/rubocop/rubocop-rails/issues/1234): Fix an incorrect autocorrect for `Rails/FindBy` when using multi-line leading dot method calls. ([@ymap][])

lib/rubocop/cop/rails/find_by.rb

@@ -59,7 +59,7 @@ def autocorrect(corrector, node)
           return if node.method?(:first)
 
           where_loc = node.receiver.loc.selector
-          first_loc = range_between(node.loc.dot.begin_pos, node.loc.selector.end_pos)
+          first_loc = range_between(node.receiver.source_range.end_pos, node.loc.selector.end_pos)
 
           corrector.replace(where_loc, 'find_by')
           corrector.replace(first_loc, '')

spec/rubocop/cop/rails/find_by_spec.rb

@@ -34,6 +34,34 @@
     RUBY
   end
 
+  it 'registers and corrects an offense when using multi-line leading dot method calls' do
+    expect_offense(<<~RUBY)
+      User
+        .where(id: x)
+         ^^^^^^^^^^^^ Use `find_by` instead of `where.take`.
+        .take
+    RUBY
+
+    expect_correction(<<~RUBY)
+      User
+        .find_by(id: x)
+    RUBY
+  end
+
+  it 'registers and corrects an offense when using multi-line trailing dot method calls' do
+    expect_offense(<<~RUBY)
+      User.
+        where(id: x).
+        ^^^^^^^^^^^^^ Use `find_by` instead of `where.take`.
+        take
+    RUBY
+
+    expect_correction(<<~RUBY)
+      User.
+        find_by(id: x)
+    RUBY
+  end
+
   context 'when using safe navigation operator' do
     it 'registers an offense when using `#take`' do
       expect_offense(<<~RUBY)