From 783c99e6c7e0f173f8d804d2909522ce3041e8dc Mon Sep 17 00:00:00 2001
From: Augustin Gottlieb <33221555+aguspe@users.noreply.github.com>
Date: Fri, 2 Jan 2026 17:54:42 +0100
Subject: [PATCH] Improve Argument Error Message in EC:Group.new

Before, passing the wrong number of arguments (e.g., 2) to
OpenSSL::PKey::EC::Group.new raised a generic "wrong number of
arguments"
error.

This change updates it to show the actual argument count and the
expected
options (1 or 4), making debugging easier for the user.

Example:
ArgumentError: wrong number of arguments (given 2, expected 1 or 4)

I hope it helps!
---
 ext/openssl/ossl_pkey_ec.c   | 2 +-
 test/openssl/test_pkey_ec.rb | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/ext/openssl/ossl_pkey_ec.c b/ext/openssl/ossl_pkey_ec.c
index bb19533ed..35f031819 100644
--- a/ext/openssl/ossl_pkey_ec.c
+++ b/ext/openssl/ossl_pkey_ec.c
@@ -702,7 +702,7 @@ static VALUE ossl_ec_group_initialize(int argc, VALUE *argv, VALUE self)
 
         break;
       default:
-        ossl_raise(rb_eArgError, "wrong number of arguments");
+        ossl_raise(rb_eArgError, "wrong number of arguments (given %d, expected 1 or 4)", argc);
     }
 
     ASSUME(group);
diff --git a/test/openssl/test_pkey_ec.rb b/test/openssl/test_pkey_ec.rb
index 88085bc68..ec97a747a 100644
--- a/test/openssl/test_pkey_ec.rb
+++ b/test/openssl/test_pkey_ec.rb
@@ -345,6 +345,15 @@ def test_ec_group
     assert_equal group1.degree, group4.degree
   end
 
+  def test_ec_group_initialize_error_message
+    # Test that passing 2 arguments raises the helpful error
+    e = assert_raise(ArgumentError) do
+      OpenSSL::PKey::EC::Group.new(:GFp, 123)
+    end
+
+    assert_equal("wrong number of arguments (given 2, expected 1 or 4)", e.message)
+  end
+
   def test_ec_point
     group = OpenSSL::PKey::EC::Group.new("prime256v1")
     key = OpenSSL::PKey::EC.generate(group)