fixes #13605 (#13611)

changelog.md

@@ -115,6 +115,9 @@ echo f
   serve no purpose whatsoever.
 - `httpclient.newHttpClient` and `httpclient.newAsyncHttpClient` added `headers`
   argument to set initial HTTP Headers, instead of a hardcoded empty `newHttpHeader()`.
+- `parseutils.parseUntil` has now a different behaviour if the `until` parameter is
+  empty. This was required for intuitive behaviour of the strscans module
+  (see bug #13605).
 
 
 ## Language additions

lib/pure/parseutils.nim

@@ -354,12 +354,13 @@ proc parseUntil*(s: string, token: var string, until: string,
     doAssert myToken == "Hello "
     doAssert parseUntil("Hello World", myToken, "Wor", 2) == 4
     doAssert myToken == "llo "
-  if until.len == 0:
-    token.setLen(0)
-    return 0
+  when (NimMajor, NimMinor) <= (1, 0):
+    if until.len == 0:
+      token.setLen(0)
+      return 0
   var i = start
   while i < s.len:
-    if s[i] == until[0]:
+    if until.len > 0 and s[i] == until[0]:
       var u = 1
       while i+u < s.len and u < until.len and s[i+u] == until[u]:
         inc u