vim-patch:9.0.1617: charidx() result is not consistent with byteidx() (#23963)

Problem:    charidx() and utf16idx() result is not consistent with byteidx().
Solution:   When the index is equal to the length of the text return the
            lenght of the text instead of -1. (Yegappan Lakshmanan,
            closes vim/vim#12503)

https://github.com/vim/vim/commit/577922b917e48285a7a312daf7b5bbc6e272939c

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index 4e521b14f7..a0d62f5df5 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -1603,6 +1603,11 @@ void f_charidx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   int len;
   for (p = str, len = 0; utf16idx ? idx >= 0 : p <= str + idx; len++) {
     if (*p == NUL) {
+      // If the index is exactly the number of bytes or utf-16 code units
+      // in the string then return the length of the string in characters.
+      if (utf16idx ? (idx == 0) : (p == (str + idx))) {
+        rettv->vval.v_number = len;
+      }
       return;
     }
     if (utf16idx) {
@@ -2047,6 +2052,11 @@ void f_utf16idx(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   int len;
   for (p = str, len = 0; charidx ? idx >= 0 : p <= str + idx; len++) {
     if (*p == NUL) {
+      // If the index is exactly the number of bytes or characters in the
+      // string then return the length of the string in utf-16 code units.
+      if (charidx ? (idx == 0) : (p == (str + idx))) {
+        rettv->vval.v_number = len;
+      }
       return;
     }
     const int clen = ptr2len(p);