Adapt to change in strutils.split

Fixes #15
Related to nim-lang/Nim#4361

Author: oprypin

src/docopt.nim

@@ -164,7 +164,7 @@ method fix_repeating_arguments(self: Pattern) {.base.} =
                 if e.value.kind == vkNone:
                     e.value = val(@[])
                 elif e.value.kind != vkList:
-                    e.value = val(($e.value).split())
+                    e.value = val(($e.value).split_whitespace())
             if e.class == "Command" or
               e.class == "Option" and Option(e).argcount == 0:
                 e.value = val(0)
@@ -250,7 +250,7 @@ proc option_parse[T](
     var (options, p, description) = option_description.strip().partition("  ")
     discard p
     options = options.replace(",", " ").replace("=", " ")
-    for s in options.split():
+    for s in options.split_whitespace():
         if s.starts_with "--":
             long = s
         elif s.starts_with "-":
@@ -338,7 +338,7 @@ proc `@`(tokens: TokenStream): var seq[string] = tokens.tokens
 proc token_stream(source: seq[string], error: ref Exception): TokenStream =
     TokenStream(tokens: source, error: error)
 proc token_stream(source: string, error: ref Exception): TokenStream =
-    token_stream(source.split(), error)
+    token_stream(source.split_whitespace(), error)
 
 proc current(self: TokenStream): string =
     if @self.len > 0:
@@ -549,7 +549,7 @@ proc printable_usage(doc: string): string =
 
 
 proc formal_usage(printable_usage: string): string =
-    var pu = printable_usage.split()
+    var pu = printable_usage.split_whitespace()
     pu.delete(0)
     var pu0 = pu[0]
     pu.delete(0)

src/private/util.nim

@@ -57,3 +57,9 @@ macro gen_class*(body: stmt): stmt {.immediate.} =
         meth &= "= \"$1\""
         body.add(parse_stmt(meth.format(typ[0])))
     body
+
+
+# Backwards compatibility
+when not compiles("".split_whitespace()):
+    proc split_whitespace*(s: string): seq[string] =
+        s.split()

test/test.nim

@@ -8,7 +8,7 @@ proc test(doc, args, expected_s: string): bool =
     var error = ""
     try:
         try:
-            var output = docopt(doc, args.split(), quit=false)
+            var output = docopt(doc, args.split_whitespace(), quit=false)
             var expected = init_table[string, Value]()
             for k, v in expected_json:
                 expected[k] = case v.kind
@@ -68,4 +68,4 @@ for each_line in (tests & "\n\n").split_lines():
         expected = nil
 echo()
 
-quit(if passed == total: 0 else: 1)
+quit(if passed == total: 0 else: 1)