From e2b149190584e53c662d09aeee9390908bbb250f Mon Sep 17 00:00:00 2001
From: Bung <crc32@qq.com>
Date: Tue, 28 Jul 2020 17:47:22 +0800
Subject: [PATCH] Fix #11352 strutil.insertSep() fails on negative numbers
 (#15087)

* fix #11352 strutil.insertSep handle negtive number

* test for #11352

* optimize

* not parts string var

* Update lib/pure/strutils.nim

Thanks!

Co-authored-by: alaviss <leorize+oss@disroot.org>

* need to be countdown

Co-authored-by: alaviss <leorize+oss@disroot.org>
---
 lib/pure/strutils.nim                  | 23 +++++++++++++++++------
 tests/modules/tstrutils_insert_sep.nim | 13 +++++++++++++
 2 files changed, 30 insertions(+), 6 deletions(-)
 create mode 100644 tests/modules/tstrutils_insert_sep.nim

diff --git a/lib/pure/strutils.nim b/lib/pure/strutils.nim
index 32d6ede1e1..a0a172430a 100644
--- a/lib/pure/strutils.nim
+++ b/lib/pure/strutils.nim
@@ -2264,17 +2264,28 @@ proc insertSep*(s: string, sep = '_', digits = 3): string {.noSideEffect,
   ## if `s` contains a number.
   runnableExamples:
     doAssert insertSep("1000000") == "1_000_000"
-
-  var L = (s.len-1) div digits + s.len
-  result = newString(L)
+  result = newStringOfCap(s.len)
+  let hasPrefix = isDigit(s[s.low]) == false
+  var idx:int
+  if hasPrefix:
+    result.add s[s.low]
+    for i in (s.low + 1)..s.high:
+      idx = i
+      if not isDigit(s[i]):
+        result.add s[i]
+      else:
+        break
+  let partsLen = s.len - idx
+  var L = (partsLen-1) div digits + partsLen
+  result.setLen(L + idx)
   var j = 0
   dec(L)
-  for i in countdown(len(s)-1, 0):
+  for i in countdown(partsLen-1,0):
     if j == digits:
-      result[L] = sep
+      result[L + idx] = sep
       dec(L)
       j = 0
-    result[L] = s[i]
+    result[L + idx] = s[i + idx]
     inc(j)
     dec(L)
 
diff --git a/tests/modules/tstrutils_insert_sep.nim b/tests/modules/tstrutils_insert_sep.nim
new file mode 100644
index 0000000000..775fe7da10
--- /dev/null
+++ b/tests/modules/tstrutils_insert_sep.nim
@@ -0,0 +1,13 @@
+discard """
+  output: '''
+-100
+-100,000
+100,000
+'''
+"""
+# test https://github.com/nim-lang/Nim/issues/11352
+
+import strutils
+echo insertSep($(-100), ',')
+echo insertSep($(-100_000), ',')
+echo insertSep($(100_000), ',')
\ No newline at end of file