Fix exception overwritten for parameters fetch method

When executing an `ActionController::Parameters#fetch` with a block
that raises a `KeyError` the raised `KeyError` will be rescued and
converted to an `ActionController::ParameterMissing` exception,
covering up the original exception.

[Jonas Schubert Erlandsson & Roque Pinel]

1 files changed, 7 insertions, 3 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index 06d625e4d5..cf6a64009f 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -380,11 +380,15 @@ module ActionController
     def fetch(key, *args, &block)
       convert_hashes_to_parameters(
         key,
-        @parameters.fetch(key, *args, &block),
+        @parameters.fetch(key) {
+          if block_given?
+            yield
+          else
+            args.fetch(0) { raise ActionController::ParameterMissing.new(key) }
+          end
+        },
         false
       )
-    rescue KeyError
-      raise ActionController::ParameterMissing.new(key)
     end
 
     # Returns a new <tt>ActionController::Parameters</tt> instance that