vim-patch:8.2.3665: cannot use a lambda for 'tagfunc'

Problem:    Cannot use a lambda for 'tagfunc'.
Solution:   Use 'tagfunc' like 'opfunc'. (Yegappan Lakshmanan, closes vim/vim#9204)
19916a8c89

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

runtime/doc/options.txt

@@ -318,9 +318,9 @@ Some options ('completefunc', 'imactivatefunc', 'imstatusfunc', 'omnifunc',
 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)}
+	set opfunc=function('MyOpFunc')
+	set opfunc=funcref('MyOpFunc')
+	let &opfunc = "{t -> MyOpFunc(t)}"
 <
 
 Setting the filetype
@@ -6443,7 +6443,9 @@ A jump table for the options with a short description can be found at |Q_op|.
 	This option specifies a function to be used to perform tag searches.
 	The function gets the tag pattern and should return a List of matching
 	tags.  See |tag-function| for an explanation of how to write the
-	function and an example.
+	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.
 
 						*'taglength'* *'tl'*
 'taglength' 'tl'	number	(default 0)

src/nvim/buffer.c

@@ -1981,6 +1981,7 @@ void free_buf_options(buf_T *buf, int free_p_ff)
   clear_string_option(&buf->b_p_tags);
   clear_string_option(&buf->b_p_tc);
   clear_string_option(&buf->b_p_tfu);
+  callback_free(&buf->b_tfu_cb);
   clear_string_option(&buf->b_p_dict);
   clear_string_option(&buf->b_p_tsr);
   clear_string_option(&buf->b_p_qe);

src/nvim/buffer_defs.h

@@ -677,6 +677,7 @@ struct file_buffer {
   char *b_p_cfu;                ///< 'completefunc'
   char *b_p_ofu;                ///< 'omnifunc'
   char *b_p_tfu;                ///< 'tagfunc'
+  Callback b_tfu_cb;            ///< 'tagfunc' callback
   int b_p_eof;                  ///< 'endoffile'
   int b_p_eol;                  ///< 'endofline'
   int b_p_fixeol;               ///< 'fixendofline'

src/nvim/option.c

@@ -78,6 +78,7 @@
 #include "nvim/spellsuggest.h"
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
+#include "nvim/tag.h"
 #include "nvim/ui.h"
 #include "nvim/ui_compositor.h"
 #include "nvim/undo.h"
@@ -577,6 +578,7 @@ void free_all_options(void)
     }
   }
   free_operatorfunc_option();
+  free_tagfunc_option();
 }
 #endif
 
@@ -4383,6 +4385,7 @@ void buf_copy_options(buf_T *buf, int flags)
       COPY_OPT_SCTX(buf, BV_OFU);
       buf->b_p_tfu = xstrdup(p_tfu);
       COPY_OPT_SCTX(buf, BV_TFU);
+      buf_set_tfu_callback(buf);
       buf->b_p_sts = p_sts;
       COPY_OPT_SCTX(buf, BV_STS);
       buf->b_p_sts_nopaste = p_sts_nopaste;

src/nvim/optionstr.c

@@ -38,6 +38,7 @@
 #include "nvim/spellfile.h"
 #include "nvim/spellsuggest.h"
 #include "nvim/strings.h"
+#include "nvim/tag.h"
 #include "nvim/ui.h"
 #include "nvim/vim.h"
 #include "nvim/window.h"
@@ -1480,6 +1481,10 @@ char *did_set_string_option(int opt_idx, char **varp, char *oldval, char *errbuf
     if (qf_process_qftf_option() == FAIL) {
       errmsg = e_invarg;
     }
+  } else if (gvarp == &p_tfu) {  // 'tagfunc'
+    if (set_tagfunc_option() == FAIL) {
+      errmsg = e_invarg;
+    }
   } else {
     // Options that are a list of flags.
     p = NULL;

src/nvim/tag.c

@@ -114,10 +114,49 @@ static char *tagmatchname = NULL;   // name of last used tag
 static taggy_T ptag_entry = { NULL, INIT_FMARK, 0, 0, NULL };
 
 static int tfu_in_use = false;  // disallow recursive call of tagfunc
+static Callback tfu_cb;         // 'tagfunc' callback function
 
 // Used instead of NUL to separate tag fields in the growarrays.
 #define TAG_SEP 0x02
 
+/// Reads the 'tagfunc' option value and convert that to a callback value.
+/// Invoked when the 'tagfunc' option is set. The option value can be a name of
+/// a function (string), or function(<name>) or funcref(<name>) or a lambda.
+int set_tagfunc_option(void)
+{
+  callback_free(&tfu_cb);
+  callback_free(&curbuf->b_tfu_cb);
+
+  if (*curbuf->b_p_tfu == NUL) {
+    return OK;
+  }
+
+  if (option_set_callback_func(curbuf->b_p_tfu, &tfu_cb) == FAIL) {
+    return FAIL;
+  }
+
+  callback_copy(&curbuf->b_tfu_cb, &tfu_cb);
+
+  return OK;
+}
+
+#if defined(EXITFREE)
+void free_tagfunc_option(void)
+{
+  callback_free(&tfu_cb);
+}
+#endif
+
+/// Copy the global 'tagfunc' callback function to the buffer-local 'tagfunc'
+/// callback for 'buf'.
+void buf_set_tfu_callback(buf_T *buf)
+{
+  callback_free(&buf->b_tfu_cb);
+  if (tfu_cb.data.funcref != NULL && *tfu_cb.data.funcref != NUL) {
+    callback_copy(&buf->b_tfu_cb, &tfu_cb);
+  }
+}
+
 /// Jump to tag; handling of tag commands and tag stack
 ///
 /// *tag != NUL: ":tag {tag}", jump to new tag, add to tag stack
@@ -1129,7 +1168,7 @@ static int find_tagfunc_tags(char_u *pat, garray_T *ga, int *match_count, int fl
                flags & TAG_REGEXP   ? "r": "");
 
   save_pos = curwin->w_cursor;
-  result = call_vim_function(curbuf->b_p_tfu, 3, args, &rettv);
+  result = callback_call(&curbuf->b_tfu_cb, 3, args, &rettv);
   curwin->w_cursor = save_pos;  // restore the cursor position
   d->dv_refcount--;
 

src/nvim/testdir/test_tagfunc.vim

@@ -117,4 +117,54 @@ func Test_tagfunc_settagstack()
   delfunc Mytagfunc2
 endfunc
 
+" Test for different ways of setting the 'tagfunc' option
+func Test_tagfunc_callback()
+  " Test for using a function()
+  func MytagFunc1(pat, flags, info)
+    let g:MytagFunc1_args = [a:pat, a:flags, a:info]
+    return v:null
+  endfunc
+  let g:MytagFunc1_args = []
+  set tagfunc=function('MytagFunc1')
+  call assert_fails('tag abc', 'E433:')
+  call assert_equal(['abc', '', {}], g:MytagFunc1_args)
+
+  " Test for using a funcref()
+  new
+  func MytagFunc2(pat, flags, info)
+    let g:MytagFunc2_args = [a:pat, a:flags, a:info]
+    return v:null
+  endfunc
+  let g:MytagFunc2_args = []
+  set tagfunc=funcref('MytagFunc2')
+  call assert_fails('tag def', 'E433:')
+  call assert_equal(['def', '', {}], g:MytagFunc2_args)
+
+  " Test for using a lambda function
+  new
+  func MytagFunc3(pat, flags, info)
+    let g:MytagFunc3_args = [a:pat, a:flags, a:info]
+    return v:null
+  endfunc
+  let g:MytagFunc3_args = []
+  let &tagfunc= '{a, b, c -> MytagFunc3(a, b, c)}'
+  call assert_fails('tag ghi', 'E433:')
+  call assert_equal(['ghi', '', {}], g:MytagFunc3_args)
+
+  " Test for clearing the 'tagfunc' option
+  set tagfunc=''
+  set tagfunc&
+
+  call assert_fails("set tagfunc=function('abc')", "E700:")
+  call assert_fails("set tagfunc=funcref('abc')", "E700:")
+  let &tagfunc = "{a -> 'abc'}"
+  call assert_fails("echo taglist('a')", "E987:")
+
+  " cleanup
+  delfunc MytagFunc1
+  delfunc MytagFunc2
+  delfunc MytagFunc3
+  %bw!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab