vim-patch:7.4.1779

Problem:    Using negative index in strcharpart(). (Yegappan Lakshmanan)
Solution:   Assume single byte when using a negative iindex.

https://github.com/vim/vim/commit/73dfe917ba6357413aaf98a021c91add5ac6e9bc

3 files changed, 25 insertions, 13 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 9fc5256a7e..a9079c5519 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -15772,8 +15772,14 @@ static void f_strcharpart(typval_T *argvars, typval_T *rettv, FunPtr fptr) {
   if (argvars[2].v_type != VAR_UNKNOWN) {
     charlen = get_tv_number(&argvars[2]);
     while (charlen > 0 && nbyte + len < slen) {
-      len += mb_char2len(p[nbyte + len]);
-      charlen--;
+      int off = nbyte + len;
+
+      if (off < 0) {
+        len += 1;
+      } else {
+        len += mb_char2len(p[off]);
+        charlen--;
+      }
     }
   } else {
     len = slen - nbyte;    // default: all bytes that are available.
diff --git a/src/nvim/testdir/test_expr_utf8.vim b/src/nvim/testdir/test_expr_utf8.vim
index 00d5d9a63a..7bdcb4f65f 100644
--- a/src/nvim/testdir/test_expr_utf8.vim
+++ b/src/nvim/testdir/test_expr_utf8.vim
@@ -4,29 +4,35 @@ if !has('multi_byte')
 endif
 scriptencoding utf-8
 
-func Test_strgetchar()
+func Test_strgetchar_utf8()
   call assert_equal(char2nr('á'), strgetchar('áxb', 0))
   call assert_equal(char2nr('x'), strgetchar('áxb', 1))
 
-  call assert_equal(-1, strgetchar('axb', -1))
-  call assert_equal(-1, strgetchar('axb', 3))
-  call assert_equal(-1, strgetchar('', 0))
-
-  call assert_equal(char2nr('a'), strgetchar('àxb', 0))
+  call assert_equal(char2nr('a'), strgetchar('àxb', 0))
   call assert_equal(char2nr('̀'), strgetchar('àxb', 1))
-  call assert_equal(char2nr('x'), strgetchar('àxb', 2))
+  call assert_equal(char2nr('x'), strgetchar('àxb', 2))
 
   call assert_equal(char2nr('あ'), strgetchar('あaい', 0))
   call assert_equal(char2nr('a'), strgetchar('あaい', 1))
   call assert_equal(char2nr('い'), strgetchar('あaい', 2))
 endfunc
 
-func Test_strcharpart()
+func Test_strcharpart_utf8()
   call assert_equal('áxb', strcharpart('áxb', 0))
   call assert_equal('á', strcharpart('áxb', 0, 1))
   call assert_equal('x', strcharpart('áxb', 1, 1))
 
-  call assert_equal('a', strcharpart('àxb', 0, 1))
+  call assert_equal('いうeお', strcharpart('あいうeお', 1))
+  call assert_equal('い', strcharpart('あいうeお', 1, 1))
+  call assert_equal('いう', strcharpart('あいうeお', 1, 2))
+  call assert_equal('いうe', strcharpart('あいうeお', 1, 3))
+  call assert_equal('いうeお', strcharpart('あいうeお', 1, 4))
+  call assert_equal('eお', strcharpart('あいうeお', 3))
+  call assert_equal('e', strcharpart('あいうeお', 3, 1))
+
+  call assert_equal('あ', strcharpart('あいうeお', -3, 4))
+
+  call assert_equal('a', strcharpart('àxb', 0, 1))
   call assert_equal('̀', strcharpart('àxb', 1, 1))
-  call assert_equal('x', strcharpart('àxb', 2, 1))
+  call assert_equal('x', strcharpart('àxb', 2, 1))
 endfunc
diff --git a/src/nvim/version.c b/src/nvim/version.c
index 389e89b466..53435e4650 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -663,7 +663,7 @@ static int included_patches[] = {
   // 1782,
   // 1781,
   // 1780,
-  // 1779,
+  1779,
   // 1778 NA
   // 1777 NA
   // 1776 NA