Fix before_each method to handle nil parameter correctly

- Fix NoMethodError when calling before_each(nil) by clearing the array instead of assigning nil
- Update test expectations to be more specific about error types and messages

Author: ericproulx

CHANGELOG.md

@@ -7,6 +7,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#2655](https://github.com/ruby-grape/grape/pull/2655): Fix `before_each` method to handle `nil` parameter correctly - [@ericproulx](https://github.com/ericproulx).
 
 ### 3.1.0 (2026-01-25)
 
@@ -33,6 +34,7 @@
 * [#2633](https://github.com/ruby-grape/grape/pull/2633): Fix cascade reading - [@ericproulx](https://github.com/ericproulx).
 * [#2641](https://github.com/ruby-grape/grape/pull/2641): Restore support for `return` in endpoint blocks - [@ericproulx](https://github.com/ericproulx).
 * [#2642](https://github.com/ruby-grape/grape/pull/2642): Fix array allocation in base_route.rb - [@ericproulx](https://github.com/ericproulx).
+* Fix `before_each` method to handle `nil` parameter correctly - [@ericproulx](https://github.com/ericproulx).
 
 ### 3.0.1 (2025-11-24)
 

lib/grape/endpoint.rb

@@ -23,8 +23,10 @@ def before_each(new_setup = false, &block)
           return @before_each unless block
 
           @before_each << block
-        else
+        elsif new_setup
           @before_each = [new_setup]
+        else
+          @before_each.clear
         end
       end
 

spec/grape/endpoint_spec.rb

@@ -24,7 +24,7 @@ def app
 
     it 'is able to override a helper' do
       subject.get('/') { current_user }
-      expect { get '/' }.to raise_error(NameError)
+      expect { get '/' }.to raise_error(NameError, /undefined local variable or method 'current_user'/)
 
       described_class.before_each do |endpoint|
         allow(endpoint).to receive(:current_user).and_return('Bob')
@@ -34,15 +34,15 @@ def app
       expect(last_response.body).to eq('Bob')
 
       described_class.before_each(nil)
-      expect { get '/' }.to raise_error(NameError)
+      expect { get '/' }.to raise_error(NameError, /undefined local variable or method 'current_user'/)
     end
 
     it 'is able to stack helper' do
       subject.get('/') do
         authenticate_user!
         current_user
       end
-      expect { get '/' }.to raise_error(NameError)
+      expect { get '/' }.to raise_error(NoMethodError, /undefined method 'authenticate_user!' for/)
 
       described_class.before_each do |endpoint|
         allow(endpoint).to receive(:current_user).and_return('Bob')
@@ -56,7 +56,7 @@ def app
       expect(last_response.body).to eq('Bob')
 
       described_class.before_each(nil)
-      expect { get '/' }.to raise_error(NameError)
+      expect { get '/' }.to raise_error(NoMethodError, /undefined method 'authenticate_user!' for/)
     end
   end