vim-patch:partial:9.0.0202: code and help for indexof() is not ideal

Problem:    Code and help for indexof() is not ideal.
Solution:   Refactor the code, improve the help. (Yegappan Lakshmanan,
            closes vim/vim#10908)

https://github.com/vim/vim/commit/3fbf6cd355de2212e9227f57d545592aae3f688f

Skip CHECK_LIST_MATERIALIZE and set_vim_var_type().
Use tv_list_uidx() instead of lv_idx.

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

2 files changed, 84 insertions, 62 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 1168d7ff1d..35f1b7cd6f 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -4087,7 +4087,7 @@ indent({lnum})	The result is a Number, which is indent of line {lnum} in the
 
 index({object}, {expr} [, {start} [, {ic}]])			*index()*
 		Find {expr} in {object} and return its index.  See
-		|filterof()| for using a lambda to select the item.
+		|indexof()| for using a lambda to select the item.
 
 		If {object} is a |List| return the lowest index where the item
 		has a value equal to {expr}.  There is no automatic
@@ -4113,15 +4113,17 @@ index({object}, {expr} [, {start} [, {ic}]])			*index()*
 <		Can also be used as a |method|: >
 			GetObject()->index(what)
 
-indexof({object}, {expr} [, {opt}])			*indexof()*
-		{object} must be a |List| or a |Blob|.
+indexof({object}, {expr} [, {opts}])			*indexof()*
+		Returns the index of an item in {object} where {expr} is
+		v:true.  {object} must be a |List| or a |Blob|.
+
 		If {object} is a |List|, evaluate {expr} for each item in the
-		List until the expression returns v:true and return the index
-		of this item.
+		List until the expression is v:true and return the index of
+		this item.
 
 		If {object} is a |Blob| evaluate {expr} for each byte in the
-		Blob until the expression returns v:true and return the index
-		of this byte.
+		Blob until the expression is v:true and return the index of
+		this byte.
 
 		{expr} must be a |string| or |Funcref|.
 
@@ -4137,16 +4139,17 @@ indexof({object}, {expr} [, {opt}])			*indexof()*
 		The function must return |TRUE| if the item is found and the
 		search should stop.
 
-		The optional argument {opt} is a Dict and supports the
+		The optional argument {opts} is a Dict and supports the
 		following items:
-		    start	start evaluating {expr} at the item with index
-				{start} (may be negative for an item relative
-				to the end).
+		    startidx	start evaluating {expr} at the item with this
+				index; may be negative for an item relative to
+				the end
 		Returns -1 when {expr} evaluates to v:false for all the items.
 		Example: >
-			:let l = [#{n: 10}, #{n: 20}, #{n: 30]]
-			:let idx = indexof(l, "v:val.n == 20")
-			:let idx = indexof(l, {i, v -> v.n == 30})
+			:let l = [#{n: 10}, #{n: 20}, #{n: 30}]
+			:echo indexof(l, "v:val.n == 20")
+			:echo indexof(l, {i, v -> v.n == 30})
+			:echo indexof(l, "v:val.n == 20", #{startidx: 1})
 
 <		Can also be used as a |method|: >
 			mylist->indexof(expr)
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 980a9fffa3..8070dacc48 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -3509,6 +3509,71 @@ static varnumber_T indexof_eval_expr(typval_T *expr)
   return error ? false : found;
 }
 
+/// Evaluate "expr" for each byte in the Blob "b" starting with the byte at
+/// "startidx" and return the index of the byte where "expr" is TRUE.  Returns
+/// -1 if "expr" doesn't evaluate to TRUE for any of the bytes.
+static varnumber_T indexof_blob(blob_T *b, varnumber_T startidx, typval_T *expr)
+{
+  if (b == NULL) {
+    return -1;
+  }
+
+  if (startidx < 0) {
+    // negative index: index from the last byte
+    startidx = tv_blob_len(b) + startidx;
+    if (startidx < 0) {
+      startidx = 0;
+    }
+  }
+
+  for (varnumber_T idx = startidx; idx < tv_blob_len(b); idx++) {
+    set_vim_var_nr(VV_KEY, idx);
+    set_vim_var_nr(VV_VAL, tv_blob_get(b, (int)idx));
+
+    if (indexof_eval_expr(expr)) {
+      return idx;
+    }
+  }
+
+  return -1;
+}
+
+/// Evaluate "expr" for each item in the List "l" starting with the item at
+/// "startidx" and return the index of the item where "expr" is TRUE.  Returns
+/// -1 if "expr" doesn't evaluate to TRUE for any of the items.
+static varnumber_T indexof_list(list_T *l, varnumber_T startidx, typval_T *expr)
+{
+  if (l == NULL) {
+    return -1;
+  }
+
+  listitem_T *item;
+  varnumber_T idx = 0;
+  if (startidx == 0) {
+    item = tv_list_first(l);
+  } else {
+    // Start at specified item.
+    idx = tv_list_uidx(l, (int)startidx);
+    if (idx == -1) {
+      item = NULL;
+    } else {
+      item = tv_list_find(l, (int)idx);
+      assert(item != NULL);
+    }
+  }
+
+  for (; item != NULL; item = TV_LIST_ITEM_NEXT(l, item), idx++) {
+    set_vim_var_nr(VV_KEY, idx);
+    tv_copy(TV_LIST_ITEM_TV(item), get_vim_var_tv(VV_VAL));
+
+    if (indexof_eval_expr(expr)) {
+      return idx;
+    }
+  }
+
+  return -1;
+}
+
 /// "indexof()" function
 static void f_indexof(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {
@@ -3526,7 +3591,6 @@ static void f_indexof(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   }
 
   varnumber_T startidx = 0;
-  varnumber_T idx = 0;
   if (argvars[2].v_type == VAR_DICT) {
     startidx = tv_dict_get_number_def(argvars[2].vval.v_dict, "startidx", 0);
   }
@@ -3542,56 +3606,11 @@ static void f_indexof(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   did_emsg = false;
 
   if (argvars[0].v_type == VAR_BLOB) {
-    blob_T *const b = argvars[0].vval.v_blob;
-    if (b == NULL) {
-      goto theend;
-    }
-    if (startidx < 0) {
-      startidx = tv_blob_len(b) + startidx;
-      if (startidx < 0) {
-        startidx = 0;
-      }
-    }
-
-    for (idx = startidx; idx < tv_blob_len(b); idx++) {
-      set_vim_var_nr(VV_KEY, idx);
-      set_vim_var_nr(VV_VAL, tv_blob_get(b, (int)idx));
-
-      if (indexof_eval_expr(&argvars[1])) {
-        rettv->vval.v_number = idx;
-        break;
-      }
-    }
+    rettv->vval.v_number = indexof_blob(argvars[0].vval.v_blob, startidx, &argvars[1]);
   } else {
-    list_T *const l = argvars[0].vval.v_list;
-    if (l == NULL) {
-      goto theend;
-    }
-
-    listitem_T *item;
-    if (startidx == 0) {
-      item = tv_list_first(l);
-    } else {
-      // Start at specified item.  Use the cached index that list_find()
-      // sets, so that a negative number also works.
-      item = tv_list_find(l, (int)startidx);
-      if (item != NULL) {
-        idx = l->lv_idx;
-      }
-    }
-
-    for (; item != NULL; item = TV_LIST_ITEM_NEXT(l, item), idx++) {
-      set_vim_var_nr(VV_KEY, idx);
-      tv_copy(TV_LIST_ITEM_TV(item), get_vim_var_tv(VV_VAL));
-
-      if (indexof_eval_expr(&argvars[1])) {
-        rettv->vval.v_number = idx;
-        break;
-      }
-    }
+    rettv->vval.v_number = indexof_list(argvars[0].vval.v_list, startidx, &argvars[1]);
   }
 
-theend:
   restore_vimvar(VV_KEY, &save_key);
   restore_vimvar(VV_VAL, &save_val);
   did_emsg |= save_did_emsg;