feat(prompt): prompt_getinput() gets current input #34491

Problem:
Not easy to get user-input in prompt-buffer before the user submits the
input. Under the current system user/plugin needs to read the buffer
contents, figure out where the prompt is, then extract the text.

Solution:
- Add prompt_getinput().
- Extract prompt text extraction logic to a separate function

runtime/doc/news.txt

@@ -151,6 +151,8 @@ EDITOR
 • |omnicompletion| in `help` buffer. |ft-help-omni|
 • Setting "'0" in 'shada' prevents storing the jumplist in the shada file.
 • 'shada' now correctly respects "/0" and "f0".
+• |prompt-buffer| supports multiline input/paste, undo/redo, and o/O normal
+  commands.
 
 EVENTS
 
@@ -253,6 +255,7 @@ UI
 VIMSCRIPT
 
 • |cmdcomplete_info()| gets current cmdline completion info.
+• |prompt_getinput()| gets current user-input in prompt-buffer.
 
 ==============================================================================
 CHANGED FEATURES                                                 *news-changed*

runtime/doc/vim_diff.txt

@@ -333,6 +333,7 @@ Functions:
 - |tempname()| tries to recover if the Nvim |tempdir| disappears.
 - |writefile()| with "p" flag creates parent directories.
 - |searchcount()|'s maximal value is raised from 99 to 999.
+- |prompt_getinput()|
 
 Highlight groups:
 - |highlight-blend| controls blend level for a highlight group

runtime/doc/vimfn.txt

@@ -7548,6 +7548,19 @@ printf({fmt}, {expr1} ...)                                            *printf()*
                 Return: ~
                   (`string`)
 
+prompt_getinput({buf})                                       *prompt_getinput()*
+		Gets the current user-input in |prompt-buffer| {buf} without invoking
+		prompt_callback. {buf} can be a buffer name or number.
+
+		If the buffer doesn't exist or isn't a prompt buffer, an empty
+		string is returned.
+
+                Parameters: ~
+                  • {buf} (`integer|string`)
+
+                Return: ~
+                  (`any`)
+
 prompt_getprompt({buf})                                     *prompt_getprompt()*
 		Returns the effective prompt text for buffer {buf}.  {buf} can
 		be a buffer name or number.  See |prompt-buffer|.

runtime/lua/vim/_meta/vimfn.lua

@@ -6867,6 +6867,16 @@ function vim.fn.prevnonblank(lnum) end
 --- @return string
 function vim.fn.printf(fmt, expr1) end
 
+--- Gets the current user-input in |prompt-buffer| {buf} without invoking
+--- prompt_callback. {buf} can be a buffer name or number.
+---
+--- If the buffer doesn't exist or isn't a prompt buffer, an empty
+--- string is returned.
+---
+--- @param buf integer|string
+--- @return any
+function vim.fn.prompt_getinput(buf) end
+
 --- Returns the effective prompt text for buffer {buf}.  {buf} can
 --- be a buffer name or number.  See |prompt-buffer|.
 ---

src/nvim/edit.c

@@ -1078,7 +1078,7 @@ check_pum:
       return 0;
     }
     if ((mod_mask & MOD_MASK_SHIFT) == 0 && bt_prompt(curbuf)) {
-      invoke_prompt_callback();
+      prompt_invoke_callback();
       if (!bt_prompt(curbuf)) {
         // buffer changed to a non-prompt buffer, get out of
         // Insert mode

src/nvim/eval.c

@@ -8660,24 +8660,16 @@ void eval_fmt_source_name_line(char *buf, size_t bufsize)
   }
 }
 
-void invoke_prompt_callback(void)
+/// Gets the current user-input in prompt buffer `buf`, or NULL if buffer is not a prompt buffer.
+char *prompt_get_input(buf_T *buf)
 {
-  typval_T rettv;
-  typval_T argv[2];
-  linenr_T lnum_start = curbuf->b_prompt_start.mark.lnum;
-  linenr_T lnum_last = curbuf->b_ml.ml_line_count;
-
-  // Add a new line for the prompt before invoking the callback, so that
-  // text can always be inserted above the last line.
-  ml_append(lnum_last, "", 0, false);
-  appended_lines_mark(lnum_last, 1);
-  curwin->w_cursor.lnum = lnum_last + 1;
-  curwin->w_cursor.col = 0;
-
-  if (curbuf->b_prompt_callback.type == kCallbackNone) {
-    goto theend;
+  if (!bt_prompt(buf)) {
+    return NULL;
   }
-  char *text = ml_get(lnum_start);
+  linenr_T lnum_start = buf->b_prompt_start.mark.lnum;
+  linenr_T lnum_last = buf->b_ml.ml_line_count;
+
+  char *text = ml_get_buf(buf, lnum_start);
   char *prompt = prompt_text();
   if (strlen(text) >= strlen(prompt)) {
     text += strlen(prompt);
@@ -8687,11 +8679,39 @@ void invoke_prompt_callback(void)
   for (linenr_T i = lnum_start + 1; i <= lnum_last; i++) {
     char *half_text = concat_str(full_text, "\n");
     xfree(full_text);
-    full_text = concat_str(half_text, ml_get(i));
+    full_text = concat_str(half_text, ml_get_buf(buf, i));
     xfree(half_text);
   }
+  return full_text;
+}
+
+/// Invokes the user-defined callback defined for the current prompt-buffer.
+void prompt_invoke_callback(void)
+{
+  typval_T rettv;
+  typval_T argv[2];
+  linenr_T lnum = curbuf->b_ml.ml_line_count;
+
+  char *user_input = prompt_get_input(curbuf);
+
+  if (!user_input) {
+    return;
+  }
+
+  // Add a new line for the prompt before invoking the callback, so that
+  // text can always be inserted above the last line.
+  ml_append(lnum, "", 0, false);
+  appended_lines_mark(lnum, 1);
+  curwin->w_cursor.lnum = lnum + 1;
+  curwin->w_cursor.col = 0;
+
+  if (curbuf->b_prompt_callback.type == kCallbackNone) {
+    xfree(user_input);
+    goto theend;
+  }
+
   argv[0].v_type = VAR_STRING;
-  argv[0].vval.v_string = full_text;
+  argv[0].vval.v_string = user_input;
   argv[1].v_type = VAR_UNKNOWN;
 
   callback_call(&curbuf->b_prompt_callback, 1, argv, &rettv);

src/nvim/eval.lua

@@ -8332,6 +8332,21 @@ M.funcs = {
     signature = 'printf({fmt}, {expr1} ...)',
     returns = 'string',
   },
+  prompt_getinput = {
+    args = 1,
+    base = 1,
+    desc = [=[
+      Gets the current user-input in |prompt-buffer| {buf} without invoking
+      prompt_callback. {buf} can be a buffer name or number.
+
+      If the buffer doesn't exist or isn't a prompt buffer, an empty
+      string is returned.
+
+    ]=],
+    name = 'prompt_getinput',
+    params = { { 'buf', 'integer|string' } },
+    signature = 'prompt_getinput({buf})',
+  },
   prompt_getprompt = {
     args = 1,
     base = 1,

src/nvim/eval/funcs.c

@@ -5364,6 +5364,26 @@ static void f_prompt_setprompt(typval_T *argvars, typval_T *rettv, EvalFuncData
   buf->b_prompt_text = xstrdup(text);
 }
 
+/// "prompt_getinput({buffer})" function
+static void f_prompt_getinput(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
+  FUNC_ATTR_NONNULL_ALL
+{
+  // return an empty string by default, e.g. it's not a prompt buffer
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = NULL;
+
+  buf_T *const buf = tv_get_buf_from_arg(&argvars[0]);
+  if (buf == NULL) {
+    return;
+  }
+
+  if (!bt_prompt(buf)) {
+    return;
+  }
+
+  rettv->vval.v_string = prompt_get_input(buf);
+}
+
 /// "pum_getpos()" function
 static void f_pum_getpos(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
 {

src/nvim/normal.c

@@ -3853,7 +3853,7 @@ static void nv_down(cmdarg_T *cap)
     } else if (bt_prompt(curbuf) && cap->cmdchar == CAR
                && curwin->w_cursor.lnum == curbuf->b_ml.ml_line_count) {
       // In a prompt buffer a <CR> in the last line invokes the callback.
-      invoke_prompt_callback();
+      prompt_invoke_callback();
       if (restart_edit == 0) {
         restart_edit = 'a';
       }

test/functional/legacy/prompt_buffer_spec.lua

@@ -249,6 +249,8 @@ describe('prompt buffer', function()
 
   it('can insert multiline text', function()
     source_script()
+    local buf = api.nvim_get_current_buf()
+
     feed('line 1<s-cr>line 2<s-cr>line 3')
     screen:expect([[
       cmd: line 1              |
@@ -261,6 +263,9 @@ describe('prompt buffer', function()
       {5:-- INSERT --}             |
     ]])
 
+    -- prompt_getinput works with multiline input
+    eq('line 1\nline 2\nline 3', fn('prompt_getinput', buf))
+
     feed('<cr>')
     -- submiting multiline text works
     screen:expect([[
@@ -274,6 +279,8 @@ describe('prompt buffer', function()
       {5:-- INSERT --}             |
     ]])
 
+    eq('', fn('prompt_getinput', buf))
+
     -- % prompt is not repeated with formatoptions+=r
     source([[
       bwipeout!
@@ -293,6 +300,8 @@ describe('prompt buffer', function()
 
   it('can put (p) multiline text', function()
     source_script()
+    local buf = api.nvim_get_current_buf()
+
     fn('setreg', 'a', 'line 1\nline 2\nline 3')
     feed('<esc>"ap')
     screen:expect([[
@@ -305,6 +314,10 @@ describe('prompt buffer', function()
       {1:~                        }|*3
                                |
     ]])
+
+    -- prompt_getinput works with pasted input
+    eq('line 1\nline 2\nline 3', fn('prompt_getinput', buf))
+
     feed('i<cr>')
     screen:expect([[
       Result: "line 1          |
@@ -335,6 +348,8 @@ describe('prompt buffer', function()
 
   it('can undo current prompt', function()
     source_script()
+    local buf = api.nvim_get_current_buf()
+
     -- text editiing alowed in current prompt
     feed('tests-initial<esc>')
     feed('bimiddle-<esc>')
@@ -368,6 +383,9 @@ describe('prompt buffer', function()
       1 change; {MATCH:.*} |
     ]])
 
+    -- undo is reflected in prompt_getinput
+    eq('tests-middle-initial', fn('prompt_getinput', buf))
+
     feed('u')
     screen:expect([[
       cmd: tests-^initial       |
@@ -406,6 +424,8 @@ describe('prompt buffer', function()
 
   it('o/O can create new lines', function()
     source_script()
+    local buf = api.nvim_get_current_buf()
+
     feed('line 1<s-cr>line 2<s-cr>line 3')
     screen:expect([[
       cmd: line 1              |
@@ -419,7 +439,6 @@ describe('prompt buffer', function()
     ]])
 
     feed('<esc>koafter')
-
     screen:expect([[
       cmd: line 1              |
       line 2                   |
@@ -431,6 +450,9 @@ describe('prompt buffer', function()
       {5:-- INSERT --}             |
     ]])
 
+    -- newline created with o is reflected in prompt_getinput
+    eq('line 1\nline 2\nafter\nline 3', fn('prompt_getinput', buf))
+
     feed('<esc>kObefore')
 
     screen:expect([[
@@ -444,6 +466,9 @@ describe('prompt buffer', function()
       {5:-- INSERT --}             |
     ]])
 
+    -- newline created with O is reflected in prompt_getinput
+    eq('line 1\nbefore\nline 2\nafter\nline 3', fn('prompt_getinput', buf))
+
     feed('<cr>')
     screen:expect([[
       line 2                   |
@@ -552,4 +577,23 @@ describe('prompt buffer', function()
     source('set buftype=')
     eq("Invalid mark name: ':'", t.pcall_err(api.nvim_buf_get_mark, 0, ':'))
   end)
+
+  describe('prompt_getinput', function()
+    it('returns current prompts text', function()
+      command('new')
+      local bufnr = fn('bufnr')
+      api.nvim_set_option_value('buftype', 'prompt', { buf = 0 })
+      eq('', fn('prompt_getinput', bufnr))
+      feed('iasdf')
+      eq('asdf', fn('prompt_getinput', bufnr))
+      feed('<esc>dd')
+      eq('', fn('prompt_getinput', bufnr))
+      feed('iasdf2')
+      eq('asdf2', fn('prompt_getinput', bufnr))
+
+      -- returns empty string when called from non prompt buffer
+      api.nvim_set_option_value('buftype', '', { buf = 0 })
+      eq('', fn('prompt_getinput', bufnr))
+    end)
+  end)
 end)