Make Proc#parameters support lambda keyword for returning parameters as if lambda

This makes it easier to use Proc#parameters to build wrappers.

Implements [Feature #15357]

1 files changed, 33 insertions, 6 deletions

diff --git a/proc.c b/proc.c
index aa6f31f294..4a4ba70c87 100644
--- a/proc.c
+++ b/proc.c
@@ -1415,19 +1415,46 @@ rb_unnamed_parameters(int arity)
 
 /*
  * call-seq:
- *    prc.parameters  -> array
+ *    prc.parameters(lambda: nil)  -> array
  *
- * Returns the parameter information of this proc.
+ * Returns the parameter information of this proc.  If the lambda
+ * keyword is provided and not nil, treats the proc as a lambda if
+ * true and as a non-lambda if false.
  *
+ *    prc = proc{|x, y=42, *other|}
+ *    prc.parameters  #=> [[:opt, :x], [:opt, :y], [:rest, :other]]
  *    prc = lambda{|x, y=42, *other|}
  *    prc.parameters  #=> [[:req, :x], [:opt, :y], [:rest, :other]]
+ *    prc = proc{|x, y=42, *other|}
+ *    prc.parameters(lambda: true)  #=> [[:req, :x], [:opt, :y], [:rest, :other]]
+ *    prc = lambda{|x, y=42, *other|}
+ *    prc.parameters(lamdba: false) #=> [[:opt, :x], [:opt, :y], [:rest, :other]]
  */
 
 static VALUE
-rb_proc_parameters(VALUE self)
+rb_proc_parameters(int argc, VALUE *argv, VALUE self)
 {
-    int is_proc;
-    const rb_iseq_t *iseq = rb_proc_get_iseq(self, &is_proc);
+    static ID keyword_ids[1];
+    VALUE opt, lambda;
+    VALUE kwargs[1];
+    int is_proc ;
+    const rb_iseq_t *iseq;
+
+    iseq = rb_proc_get_iseq(self, &is_proc);
+
+    if (!keyword_ids[0]) {
+        CONST_ID(keyword_ids[0], "lambda");
+    }
+
+    rb_scan_args(argc, argv, "0:", &opt);
+    if (!NIL_P(opt)) {
+        rb_get_kwargs(opt, keyword_ids, 0, 1, kwargs);
+        lambda = kwargs[0];
+        if (!NIL_P(lambda)) {
+            is_proc = !RTEST(lambda);
+        }
+    }
+
     if (!iseq) {
 	return rb_unnamed_parameters(rb_proc_arity(self));
     }
@@ -4248,7 +4275,7 @@ Init_Proc(void)
     rb_define_method(rb_cProc, "==", proc_eq, 1);
     rb_define_method(rb_cProc, "eql?", proc_eq, 1);
     rb_define_method(rb_cProc, "source_location", rb_proc_location, 0);
-    rb_define_method(rb_cProc, "parameters", rb_proc_parameters, 0);
+    rb_define_method(rb_cProc, "parameters", rb_proc_parameters, -1);
     rb_define_method(rb_cProc, "ruby2_keywords", proc_ruby2_keywords, 0);
     // rb_define_method(rb_cProc, "isolate", rb_proc_isolate, 0); is not accepted.