From: nathanielsullivan00@... Date: 2017-11-04T19:06:23+00:00 Subject: [ruby-core:83676] [Ruby trunk Feature#14079] Validate argument list without calling method Issue #14079 has been updated by nate00 (Nate Sullivan). Oops, I think my description was somewhat misleading. I don't expect `respond_to_arguments?` to check for lines in the method body that might raise an `ArgumentError`. I expect it to check only whether the provided list of arguments matches the method signature. Maybe this example will clarify: ~~~ruby class Foobar def self.hello(str) raise ArgumentError unless str.is_a?(String) end end Foobar.respond_to_arguments?(:hello, "goodbye") # => true Foobar.respond_to_arguments?(:hello, 123) # => true, because 123 matches the method signature, even though the method will raise an ArgumentError when you call it. Foobar.respond_to_arguments?(:hello, "goodbye", "goodbye") # => false, because the method has only one parameter ~~~ So it's right to think of `respond_to_arguments?` as a method very similar to `arity` and `parameters`. Thanks for pointing out `parameters`, Eregon, I'll try that out. ---------------------------------------- Feature #14079: Validate argument list without calling method https://bugs.ruby-lang.org/issues/14079#change-67700 * Author: nate00 (Nate Sullivan) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- I would find it useful to check whether a list of arguments will cause an `ArgumentError` when passed to a method, but without calling that method. Maybe this method would be called `respond_to_arguments?`. Here's an example, where I check whether I can pass various argument lists to `String#prepend`: ~~~ruby str = "hello" # String#prepend accepts 1 argument, not 0 or 2: str.respond_to_arguments?(:prepend, "foo", "bar") # => false str.respond_to_arguments?(:prepend, "foo") # => true str.respond_to_arguments?(:prepend) # => false # Indeed, we get an ArgumentError if we pass 0 or 2 arguments: str.prepend("foo", "bar") # raises ArgumentError str.prepend("foo") # success! str.prepend # raises ArgumentError ~~~ My use case is a background job processing system. It works like this: I call `MyWorker.perform_async` with some arguments; the arguments are serialized and put into a queue; and then a background worker takes those arguments from the queue, deserializes them and passes them to `MyWorker.perform`. If I passed invalid arguments, I don't know they were invalid until the background worker tries to call `perform`. But I'd like to know immediately when I call `perform_async`. Perhaps a `respond_to_arguments_missing?` method would be required also. Maybe `respond_to_arguments?` is a bad name. You could reasonably assume that it takes the same optional second parameter as `respond_to?` (i.e., `include_all`), but my proposal doesn't support an optional second parameter. Thank you for your consideration! -- https://bugs.ruby-lang.org/ Unsubscribe: