Merge pull request #2494 from JosephTurner/fix-matching-error

Fixes matching error #2418

lib/impure/re.nim

@@ -373,23 +373,26 @@ iterator split*(s: string, sep: Regex): string =
   ## Results in:
   ##
   ## .. code-block:: nim
+  ##   ""
   ##   "this"
   ##   "is"
   ##   "an"
   ##   "example"
+  ##   ""
   ##
   var
-    first = 0
+    first = -1
-    last = 0
+    last = -1
   while last < len(s):
     var x = matchLen(s, sep, last)
     if x > 0: inc(last, x)
     first = last
+    if x == 0: inc(last)
     while last < len(s):
-      inc(last)
       x = matchLen(s, sep, last)
-      if x > 0: break
+      if x >= 0: break
-    if first < last:
+      inc(last)
+    if first <= last:
       yield substr(s, first, last-1)
 
 proc split*(s: string, sep: Regex): seq[string] =
@@ -471,7 +474,12 @@ when isMainModule:
   var accum: seq[string] = @[]
   for word in split("00232this02939is39an22example111", re"\d+"):
     accum.add(word)
-  assert(accum == @["this", "is", "an", "example"])
+  assert(accum == @["", "this", "is", "an", "example", ""])
+
+  accum = @[]
+  for word in split("AAA :   : BBB", re"\s*:\s*"):
+    accum.add(word)
+  assert(accum == @["AAA", "", "BBB"])
 
   for x in findAll("abcdef", re"^{.}", 3):
     assert x == "d"

web/news.txt

@@ -73,7 +73,11 @@ News
     for ``expr`` and ``stmt``. The new names capture the semantics much better
     and most likely  ``expr`` and ``stmt`` will be deprecated in favor of the
     new names.
-
+  - The ``split`` method in module ``re`` has changed. It now handles the case
+    of matches having a length of 0, and empty strings being yielded from the
+    iterator. A notable change might be that a pattern being matched at the
+    beginning and end of a string, will result in an empty string being produced
+    at the start and the end of the iterator.
 
   Language Additions
   ------------------