From 40d034b7e37dd3d19f324ec8bcef5fafc03fed2a Mon Sep 17 00:00:00 2001
From: Chris Heller <chris.heller@greyheller.com>
Date: Fri, 16 Dec 2016 01:33:44 -0800
Subject: [PATCH 1/4] Guard against calling split with an empty string as a
 separator. Fixes #5119

---
 lib/pure/strutils.nim    |  5 +++++
 tests/stdlib/tsplit2.nim | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 tests/stdlib/tsplit2.nim

diff --git a/lib/pure/strutils.nim b/lib/pure/strutils.nim
index 14877eb4d5..45c2669f9c 100644
--- a/lib/pure/strutils.nim
+++ b/lib/pure/strutils.nim
@@ -808,6 +808,11 @@ proc split*(s: string, sep: string, maxsplit: int = -1): seq[string] {.noSideEff
   ##
   ## Substrings are separated by the string `sep`. This is a wrapper around the
   ## `split iterator <#split.i,string,string>`_.
+  ##
+  ## If `sep` is an empty string, `ValueError` is raised.
+  if sep.len == 0:
+    raise newException(ValueError, "invalid separator: empty string not allowed")
+  
   accumulateResult(split(s, sep, maxsplit))
 
 proc rsplit*(s: string, seps: set[char] = Whitespace,
diff --git a/tests/stdlib/tsplit2.nim b/tests/stdlib/tsplit2.nim
new file mode 100644
index 0000000000..5c4245d54d
--- /dev/null
+++ b/tests/stdlib/tsplit2.nim
@@ -0,0 +1,19 @@
+discard """
+  file: "tsplit2.nim"
+  output: "true"
+"""
+import strutils
+
+var s = ""
+for w in split("|abc|xy|z", {'|'}):
+  s.add("#")
+  s.add(w)
+
+try:
+  discard "hello".split("")
+  echo "false"
+except ValueError:
+  echo "true"
+
+#OUT true
+

From 80a727f1ce74ebb3b4cf0c5a6f75d894638512c8 Mon Sep 17 00:00:00 2001
From: Chris Heller <chris.heller@greyheller.com>
Date: Wed, 21 Dec 2016 12:15:33 -0800
Subject: [PATCH 2/4] Change error handling to use assert as per Araq's comment

---
 lib/pure/strutils.nim | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/lib/pure/strutils.nim b/lib/pure/strutils.nim
index 45c2669f9c..314c94909a 100644
--- a/lib/pure/strutils.nim
+++ b/lib/pure/strutils.nim
@@ -808,10 +808,7 @@ proc split*(s: string, sep: string, maxsplit: int = -1): seq[string] {.noSideEff
   ##
   ## Substrings are separated by the string `sep`. This is a wrapper around the
   ## `split iterator <#split.i,string,string>`_.
-  ##
-  ## If `sep` is an empty string, `ValueError` is raised.
-  if sep.len == 0:
-    raise newException(ValueError, "invalid separator: empty string not allowed")
+  assert(sep.len > 0)
   
   accumulateResult(split(s, sep, maxsplit))
 

From af63bd4e0b45bad7985de829d311a8c84a99006b Mon Sep 17 00:00:00 2001
From: Chris Heller <chris.heller@greyheller.com>
Date: Wed, 21 Dec 2016 19:06:11 -0800
Subject: [PATCH 3/4] Update unit test to handle AssertionError instead of
 ValueError for #5119

---
 tests/stdlib/tsplit2.nim | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/stdlib/tsplit2.nim b/tests/stdlib/tsplit2.nim
index 5c4245d54d..7fd9dda747 100644
--- a/tests/stdlib/tsplit2.nim
+++ b/tests/stdlib/tsplit2.nim
@@ -12,7 +12,7 @@ for w in split("|abc|xy|z", {'|'}):
 try:
   discard "hello".split("")
   echo "false"
-except ValueError:
+except AssertionError:
   echo "true"
 
 #OUT true

From 7ad32ea0edc3f980f54b4bdd50ff9ac09bf74c8b Mon Sep 17 00:00:00 2001
From: Chris Heller <chris.heller@greyheller.com>
Date: Wed, 21 Dec 2016 22:24:08 -0800
Subject: [PATCH 4/4] Change error handling in split to use doAssert so it is
 not compiled out when running tests

---
 lib/pure/strutils.nim | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/pure/strutils.nim b/lib/pure/strutils.nim
index 314c94909a..8b5db49ed2 100644
--- a/lib/pure/strutils.nim
+++ b/lib/pure/strutils.nim
@@ -808,7 +808,7 @@ proc split*(s: string, sep: string, maxsplit: int = -1): seq[string] {.noSideEff
   ##
   ## Substrings are separated by the string `sep`. This is a wrapper around the
   ## `split iterator <#split.i,string,string>`_.
-  assert(sep.len > 0)
+  doAssert(sep.len > 0)
   
   accumulateResult(split(s, sep, maxsplit))