vim-patch:8.2.3619: cannot use a lambda for 'operatorfunc' (#19846)

Problem:    Cannot use a lambda for 'operatorfunc'.
Solution:   Support using a lambda or partial. (Yegappan Lakshmanan,
            closes vim/vim#8775)
https://github.com/vim/vim/commit/777175b0df8c5ec3cd30d19a2e887e661ac209c8

Omit duplicate docs. It's removed in patch 8.2.3623.
Nvim doesn't seem to need callback_set() as it was omitted when patch 8.1.1437
was first ported.

6 files changed, 163 insertions, 37 deletions

diff --git a/runtime/doc/map.txt b/runtime/doc/map.txt
index 2b2bfec6c7..ca1ddaabd4 100644
--- a/runtime/doc/map.txt
+++ b/runtime/doc/map.txt
@@ -905,6 +905,17 @@ or `unnamedplus`.
 The `mode()` function will return the state as it will be after applying the
 operator.
 
+Here is an example for using a lambda function to create a normal-mode
+operator to add quotes around text in the current line: >
+
+	nnoremap <F4> <Cmd>let &opfunc='{t ->
+				\ getline(".")
+				\ ->split("\\zs")
+				\ ->insert("\"", col("'']"))
+				\ ->insert("\"", col("''[") - 1)
+				\ ->join("")
+				\ ->setline(".")}'<CR>g@
+
 ==============================================================================
 2. Abbreviations			*abbreviations* *Abbreviations*
 
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index a1f2eac5ed..27aa06e18b 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -312,6 +312,17 @@ Note: In the future more global options can be made |global-local|.  Using
 ":setlocal" on a global option might work differently then.
 
 
+						*option-value-function*
+Some options ('completefunc', 'imactivatefunc', 'imstatusfunc', 'omnifunc',
+'operatorfunc', 'quickfixtextfunc' and 'tagfunc') are set to a function name
+or a function reference or a lambda function.  Examples:
+>
+	set opfunc=MyOpFunc
+	set opfunc=function("MyOpFunc")
+	set opfunc=funcref("MyOpFunc")
+	set opfunc={t\ ->\ MyOpFunc(t)}
+<
+
 Setting the filetype
 
 :setf[iletype] [FALLBACK] {filetype}			*:setf* *:setfiletype*
@@ -4402,7 +4413,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 'operatorfunc' 'opfunc'	string	(default: empty)
 			global
 	This option specifies a function to be called by the |g@| operator.
-	See |:map-operator| for more info and an example.
+	See |:map-operator| for more info and an example.  The value can be
+	the name of a function, a |lambda| or a |Funcref|. See
+	|option-value-function| for more information.
 
 	This option cannot be set from a |modeline| or in the |sandbox|, for
 	security reasons.
@@ -4696,8 +4709,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 	customize the information displayed in the quickfix or location window
 	for each entry in the corresponding quickfix or location list.  See
 	|quickfix-window-function| for an explanation of how to write the
-	function and an example. The value can be the name of a function or a
-	lambda.
+	function and an example.  The value can be the name of a function, a
+	|lambda| or a |Funcref|. See |option-value-function| for more
+	information.
 
 	This option cannot be set from a |modeline| or in the |sandbox|, for
 	security reasons.
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index c3edc5b315..b4fc7534bc 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -6136,6 +6136,23 @@ static void op_colon(oparg_T *oap)
   // do_cmdline() does the rest
 }
 
+/// callback function for 'operatorfunc'
+static Callback opfunc_cb;
+
+/// Process the 'operatorfunc' option value.
+/// @return  OK or FAIL
+int set_operatorfunc_option(void)
+{
+  return option_set_callback_func(p_opfunc, &opfunc_cb);
+}
+
+#if defined(EXITFREE)
+void free_operatorfunc_option(void)
+{
+  callback_free(&opfunc_cb);
+}
+#endif
+
 /// Handle the "g@" operator: call 'operatorfunc'.
 static void op_function(const oparg_T *oap)
   FUNC_ATTR_NONNULL_ALL
@@ -6173,7 +6190,10 @@ static void op_function(const oparg_T *oap)
     // Reset finish_op so that mode() returns the right value.
     finish_op = false;
 
-    (void)call_func_retnr((char *)p_opfunc, 1, argv);
+    typval_T rettv;
+    if (callback_call(&opfunc_cb, 1, argv, &rettv) != FAIL) {
+      tv_clear(&rettv);
+    }
 
     virtual_op = save_virtual_op;
     finish_op = save_finish_op;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 09793cbdcf..e85a0d9ee4 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -66,6 +66,7 @@
 #include "nvim/mouse.h"
 #include "nvim/move.h"
 #include "nvim/normal.h"
+#include "nvim/ops.h"
 #include "nvim/option.h"
 #include "nvim/os/os.h"
 #include "nvim/os_unix.h"
@@ -782,6 +783,7 @@ void free_all_options(void)
       clear_string_option((char_u **)options[i].var);
     }
   }
+  free_operatorfunc_option();
 }
 #endif
 
@@ -3264,8 +3266,12 @@ static char *did_set_string_option(int opt_idx, char_u **varp, char_u *oldval, c
         }
       }
     }
-  } else if (varp == &p_qftf) {
-    if (!qf_process_qftf_option()) {
+  } else if (varp == &p_opfunc) {  // 'operatorfunc'
+    if (set_operatorfunc_option() == FAIL) {
+      errmsg = e_invarg;
+    }
+  } else if (varp == &p_qftf) {  // 'quickfixtextfunc'
+    if (qf_process_qftf_option() == FAIL) {
       errmsg = e_invarg;
     }
   } else {
@@ -6917,6 +6923,44 @@ static int fill_culopt_flags(char_u *val, win_T *wp)
   return OK;
 }
 
+/// Set the callback function value for an option that accepts a function name,
+/// lambda, et al. (e.g. 'operatorfunc', 'tagfunc', etc.)
+/// @return  OK if the option is successfully set to a function, otherwise FAIL
+int option_set_callback_func(char_u *optval, Callback *optcb)
+{
+  if (optval == NULL || *optval == NUL) {
+    callback_free(optcb);
+    return OK;
+  }
+
+  typval_T *tv;
+  if (*optval == '{'
+      || (STRNCMP(optval, "function(", 9) == 0)
+      || (STRNCMP(optval, "funcref(", 8) == 0)) {
+    // Lambda expression or a funcref
+    tv = eval_expr((char *)optval);
+    if (tv == NULL) {
+      return FAIL;
+    }
+  } else {
+    // treat everything else as a function name string
+    tv = xcalloc(1, sizeof(*tv));
+    tv->v_type = VAR_STRING;
+    tv->vval.v_string = (char *)vim_strsave(optval);
+  }
+
+  Callback cb;
+  if (!callback_from_typval(&cb, tv)) {
+    tv_free(tv);
+    return FAIL;
+  }
+
+  callback_free(optcb);
+  *optcb = cb;
+  tv_free(tv);
+  return OK;
+}
+
 /// Check an option that can be a range of string values.
 ///
 /// @param list  when true: accept a list of values
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index 1c416a872b..d04c2bc470 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -3829,38 +3829,11 @@ static buf_T *qf_find_buf(qf_info_T *qi)
   return NULL;
 }
 
-// Process the 'quickfixtextfunc' option value.
-bool qf_process_qftf_option(void)
+/// Process the 'quickfixtextfunc' option value.
+/// @return  OK or FAIL
+int qf_process_qftf_option(void)
 {
-  if (p_qftf == NULL || *p_qftf == NUL) {
-    callback_free(&qftf_cb);
-    return true;
-  }
-
-  typval_T *tv;
-  if (*p_qftf == '{') {
-    // Lambda expression
-    tv = eval_expr((char *)p_qftf);
-    if (tv == NULL) {
-      return false;
-    }
-  } else {
-    // treat everything else as a function name string
-    tv = xcalloc(1, sizeof(*tv));
-    tv->v_type = VAR_STRING;
-    tv->vval.v_string = (char *)vim_strsave(p_qftf);
-  }
-
-  Callback cb;
-  if (!callback_from_typval(&cb, tv)) {
-    tv_free(tv);
-    return false;
-  }
-
-  callback_free(&qftf_cb);
-  qftf_cb = cb;
-  tv_free(tv);
-  return true;
+  return option_set_callback_func(p_qftf, &qftf_cb);
 }
 
 /// Update the w:quickfix_title variable in the quickfix/location list window in
diff --git a/src/nvim/testdir/test_normal.vim b/src/nvim/testdir/test_normal.vim
index 347404a579..2092b508ea 100644
--- a/src/nvim/testdir/test_normal.vim
+++ b/src/nvim/testdir/test_normal.vim
@@ -352,6 +352,70 @@ func Test_normal09a_operatorfunc()
   norm V10j,,
   call assert_equal(22, g:a)
 
+  " Use a lambda function for 'opfunc'
+  unmap <buffer> ,,
+  call cursor(1, 1)
+  let g:a=0
+  nmap <buffer><silent> ,, :set opfunc={type\ ->\ CountSpaces(type)}<CR>g@
+  vmap <buffer><silent> ,, :<C-U>call CountSpaces(visualmode(), 1)<CR>
+  50
+  norm V2j,,
+  call assert_equal(6, g:a)
+  norm V,,
+  call assert_equal(2, g:a)
+  norm ,,l
+  call assert_equal(0, g:a)
+  50
+  exe "norm 0\<c-v>10j2l,,"
+  call assert_equal(11, g:a)
+  50
+  norm V10j,,
+  call assert_equal(22, g:a)
+
+  " use a partial function for 'opfunc'
+  let g:OpVal = 0
+  func! Test_opfunc1(x, y, type)
+    let g:OpVal =  a:x + a:y
+  endfunc
+  set opfunc=function('Test_opfunc1',\ [5,\ 7])
+  normal! g@l
+  call assert_equal(12, g:OpVal)
+  " delete the function and try to use g@
+  delfunc Test_opfunc1
+  call test_garbagecollect_now()
+  call assert_fails('normal! g@l', 'E117:')
+  set opfunc=
+
+  " use a funcref for 'opfunc'
+  let g:OpVal = 0
+  func! Test_opfunc2(x, y, type)
+    let g:OpVal =  a:x + a:y
+  endfunc
+  set opfunc=funcref('Test_opfunc2',\ [4,\ 3])
+  normal! g@l
+  call assert_equal(7, g:OpVal)
+  " delete the function and try to use g@
+  delfunc Test_opfunc2
+  call test_garbagecollect_now()
+  call assert_fails('normal! g@l', 'E933:')
+  set opfunc=
+
+  " Try to use a function with two arguments for 'operatorfunc'
+  let g:OpVal = 0
+  func! Test_opfunc3(x, y)
+    let g:OpVal = 4
+  endfunc
+  set opfunc=Test_opfunc3
+  call assert_fails('normal! g@l', 'E119:')
+  call assert_equal(0, g:OpVal)
+  set opfunc=
+  delfunc Test_opfunc3
+  unlet g:OpVal
+
+  " Try to use a lambda function with two arguments for 'operatorfunc'
+  set opfunc={x,\ y\ ->\ 'done'}
+  call assert_fails('normal! g@l', 'E119:')
+
   " clean up
   unmap <buffer> ,,
   set opfunc=