vim-patch:9.0.0837: append() reports failure when not appending anything

Problem:    append() reports failure when not appending anything.
Solution:   Only report failure when appending something. (closes vim/vim#11498)

https://github.com/vim/vim/commit/cd9c8d400c1eb9cbb4ff6a33be02f91a30ab13b2

Co-authored-by: Bram Moolenaar <Bram@vim.org>

2 files changed, 20 insertions, 12 deletions

diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 079052b658..75f6cd4313 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -73,7 +73,8 @@ append({lnum}, {text})                                                *append()*
 		{lnum} can be zero to insert a line before the first one.
 		{lnum} is used like with |getline()|.
 		Returns 1 for failure ({lnum} out of range or out of memory),
-		0 for success.  Example: >vim
+		0 for success.  When {text} is an empty list zero is returned,
+		no matter the value of {lnum}.  Example: >vim
 			let failed = append(line('$'), "# THE END")
 			let failed = append(0, ["Chapter 1", "the beginning"])
 <
@@ -96,7 +97,8 @@ appendbufline({buf}, {lnum}, {text})                           *appendbufline()*
 		If {buf} is not a valid buffer or {lnum} is not valid, an
 		error message is given. Example: >vim
 			let failed = appendbufline(13, 0, "# THE START")
-<
+<		However, when {text} is an empty list then no error is given
+		for an invalid {lnum}, since {lnum} isn't actually used.
 
 argc([{winid}])                                                         *argc()*
 		The result is the number of files in the argument list.  See
@@ -6213,9 +6215,10 @@ setbufline({buf}, {lnum}, {text})                                 *setbufline()*
 
 		To insert lines use |appendbufline()|.
 
-		{text} can be a string to set one line, or a list of strings
-		to set multiple lines.  If the list extends below the last
-		line then those lines are added.
+		{text} can be a string to set one line, or a List of strings
+		to set multiple lines.  If the List extends below the last
+		line then those lines are added.  If the List is empty then
+		nothing is changed and zero is returned.
 
 		For the use of {buf}, see |bufname()| above.
 
@@ -6374,7 +6377,8 @@ setline({lnum}, {text})                                              *setline()*
 		When {lnum} is just below the last line the {text} will be
 		added below the last line.
 		{text} can be any type or a List of any type, each item is
-		converted to a String.
+		converted to a String.  When {text} is an empty List then
+		nothing is changed and FALSE is returned.
 
 		If this succeeds, FALSE is returned.  If this fails (most likely
 		because {lnum} is invalid) TRUE is returned.
diff --git a/runtime/lua/vim/_meta/vimfn.lua b/runtime/lua/vim/_meta/vimfn.lua
index e393844724..126abb29ac 100644
--- a/runtime/lua/vim/_meta/vimfn.lua
+++ b/runtime/lua/vim/_meta/vimfn.lua
@@ -79,7 +79,8 @@ function vim.fn.api_info() end
 --- {lnum} can be zero to insert a line before the first one.
 --- {lnum} is used like with |getline()|.
 --- Returns 1 for failure ({lnum} out of range or out of memory),
---- 0 for success.  Example: >vim
+--- 0 for success.  When {text} is an empty list zero is returned,
+--- no matter the value of {lnum}.  Example: >vim
 ---   let failed = append(line('$'), "# THE END")
 ---   let failed = append(0, ["Chapter 1", "the beginning"])
 --- <
@@ -106,7 +107,8 @@ function vim.fn.append(lnum, text) end
 --- If {buf} is not a valid buffer or {lnum} is not valid, an
 --- error message is given. Example: >vim
 ---   let failed = appendbufline(13, 0, "# THE START")
---- <
+--- <However, when {text} is an empty list then no error is given
+--- for an invalid {lnum}, since {lnum} isn't actually used.
 ---
 --- @param buf any
 --- @param lnum integer
@@ -7398,9 +7400,10 @@ function vim.fn.serverstop(address) end
 ---
 --- To insert lines use |appendbufline()|.
 ---
---- {text} can be a string to set one line, or a list of strings
---- to set multiple lines.  If the list extends below the last
---- line then those lines are added.
+--- {text} can be a string to set one line, or a List of strings
+--- to set multiple lines.  If the List extends below the last
+--- line then those lines are added.  If the List is empty then
+--- nothing is changed and zero is returned.
 ---
 --- For the use of {buf}, see |bufname()| above.
 ---
@@ -7602,7 +7605,8 @@ function vim.fn.setfperm(fname, mode) end
 --- When {lnum} is just below the last line the {text} will be
 --- added below the last line.
 --- {text} can be any type or a List of any type, each item is
---- converted to a String.
+--- converted to a String.  When {text} is an empty List then
+--- nothing is changed and FALSE is returned.
 ---
 --- If this succeeds, FALSE is returned.  If this fails (most likely
 --- because {lnum} is invalid) TRUE is returned.