added conversions

spec/convert_spec.lua

@@ -0,0 +1,33 @@
+local argparse = require "argparse"
+
+describe("tests related to converters", function()
+   it("converts arguments", function()
+      local parser = argparse.parser()
+      parser:argument "numbers" {
+         convert = tonumber,
+         args = "+"
+      }
+
+      local args = parser:parse{"1", "2", "500"}
+      assert.same({numbers = {1, 2, 500}}, args)
+   end)
+
+   it("raises an error when it can't convert", function()
+      local parser = argparse.parser()
+      parser:argument "numbers" {
+         convert = tonumber,
+         args = "+"
+      }
+
+      assert.has_error(function() parser:parse{"foo", "bar", "baz"} end, "malformed argument foo")
+   end)
+
+   it("second return value is used as error message", function()
+      local parser = argparse.parser()
+      parser:argument "numbers" {
+         convert = function(x) return tonumber(x), x .. " is not a number" end
+      }
+
+      assert.has_error(function() parser:parse{"foo"} end, "foo is not a number")
+   end)
+end)