paste: handle vim.paste() failure

- Show error only once per "paste stream".
- Drain remaining chunks until phase=3.
- Lay groundwork for "cancel".
- Constrain semantics of "cancel" to mean "client must stop"; it is
  unrelated to presence of error(s).

4 files changed, 113 insertions, 23 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 3631fbff66..910b76d02d 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -1206,7 +1206,7 @@ Dictionary nvim_get_namespaces(void)
   return retval;
 }
 
-/// Paste
+/// Pastes at cursor, in any mode.
 ///
 /// Invokes the `vim.paste` handler, which handles each mode appropriately.
 /// Sets redo/undo. Faster than |nvim_input()|.
@@ -1219,29 +1219,44 @@ Dictionary nvim_get_namespaces(void)
 ///                 - 2: continues the paste (zero or more times)
 ///                 - 3: ends the paste (exactly once)
 /// @param[out] err Error details, if any
-/// @return true if paste should continue, false if paste was canceled
+/// @return
+///     - true: Client may continue pasting.
+///     - false: Client must cancel the paste.
 Boolean nvim_paste(String data, Integer phase, Error *err)
   FUNC_API_SINCE(6)
 {
+  static bool draining = false;
+  bool cancel = false;
+
   if (phase < -1 || phase > 3) {
     api_set_error(err, kErrorTypeValidation, "Invalid phase: %"PRId64, phase);
     return false;
   }
-  if (!(State & CMDLINE) && !(State & INSERT) && (phase == -1 || phase == 1)) {
-    ResetRedobuff();
-    AppendCharToRedobuff('a');  // Dot-repeat.
+  Array args = ARRAY_DICT_INIT;
+  Object rv = OBJECT_INIT;
+  if (phase == -1 || phase == 1) {  // Start of paste-stream.
+    draining = false;
+  } else if (draining) {
+    // Skip remaining chunks.  Report error only once per "stream".
+    goto theend;
   }
   Array lines = string_to_array(data);
-  Array args = ARRAY_DICT_INIT;
   ADD(args, ARRAY_OBJ(lines));
   ADD(args, INTEGER_OBJ(phase));
-  Object rv
-    = nvim_execute_lua(STATIC_CSTR_AS_STRING("return vim._paste(...)"),
-                       args, err);
-  // Abort paste if handler does not return true.
-  bool ok = !ERROR_SET(err)
-    && (rv.type == kObjectTypeBoolean && rv.data.boolean);
-  if (ok && !(State & CMDLINE)) {  // Dot-repeat.
+  rv = nvim_execute_lua(STATIC_CSTR_AS_STRING("return vim._paste(...)"), args,
+                        err);
+  if (ERROR_SET(err)) {
+    draining = true;
+    goto theend;
+  }
+  if (!(State & CMDLINE) && !(State & INSERT) && (phase == -1 || phase == 1)) {
+    ResetRedobuff();
+    AppendCharToRedobuff('a');  // Dot-repeat.
+  }
+  // vim.paste() decides if client should cancel.  Errors do NOT cancel: we
+  // want to drain remaining chunks (rather than divert them to main input).
+  cancel = (rv.type != kObjectTypeBoolean || !rv.data.boolean);
+  if (!cancel && !(State & CMDLINE)) {  // Dot-repeat.
     for (size_t i = 0; i < lines.size; i++) {
       String s = lines.items[i].data.string;
       assert(data.size <= INT_MAX);
@@ -1252,20 +1267,21 @@ Boolean nvim_paste(String data, Integer phase, Error *err)
       }
     }
   }
-  api_free_object(rv);
-  api_free_array(args);
   if (!(State & CMDLINE) && !(State & INSERT) && (phase == -1 || phase == 3)) {
     AppendCharToRedobuff(ESC);  // Dot-repeat.
   }
-  if (phase == -1 || phase == 3) {
+theend:
+  api_free_object(rv);
+  api_free_array(args);
+  if (cancel || phase == -1 || phase == 3) {  // End of paste-stream.
     // XXX: Tickle main loop to ensure cursor is updated.
     loop_schedule_deferred(&main_loop, event_create(loop_dummy_event, 0));
   }
 
-  return ok;
+  return !cancel;
 }
 
-/// Puts text at cursor.
+/// Puts text at cursor, in any mode.
 ///
 /// Compare |:put| and |p| which are always linewise.
 ///
diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index f9f39c36ff..c74ef58ba1 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -107,13 +107,12 @@ static void tinput_wait_enqueue(void **argv)
     const String keys = { .data = buf, .size = len };
     if (input->paste) {
       Error err = ERROR_INIT;
-      Boolean rv = nvim_paste(keys, input->paste, &err);
-      // Paste phase: "continue" (unless handler failed).
-      input->paste = rv && !ERROR_SET(&err) ? 2 : 0;
+      // Paste phase: "continue" (unless handler canceled).
+      input->paste = !nvim_paste(keys, input->paste, &err)
+        ? 0 : (1 == input->paste ? 2 : input->paste);
       rbuffer_consumed(input->key_buffer, len);
       rbuffer_reset(input->key_buffer);
       if (ERROR_SET(&err)) {
-        msg_putchar('\n');
         // TODO(justinmk): emsgf() does not display, why?
         msg_printf_attr(HL_ATTR(HLF_E)|MSG_HIST, "paste: %s", err.msg);
         api_clear_error(&err);
@@ -373,7 +372,7 @@ static bool handle_bracketed_paste(TermInput *input)
       tinput_flush(input, true);
       // Paste phase: "first-chunk".
       input->paste = 1;
-    } else if (input->paste != 0) {
+    } else if (input->paste) {
       // Paste phase: "last-chunk".
       input->paste = input->paste == 2 ? 3 : -1;
       tinput_flush(input, true);
diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index 212c4f4300..01e4a3a1a0 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -395,6 +395,11 @@ describe('API', function()
       eq({0,3,6,0}, funcs.getpos('.'))
       eq(false, nvim('get_option', 'paste'))
     end)
+    it('vim.paste() failure', function()
+      nvim('execute_lua', 'vim._paste = (function(lines, phase) error("fake fail") end)', {})
+      expect_err([[Error executing lua: %[string "%<nvim>"]:1: fake fail]],
+        request, 'nvim_paste', 'line 1\nline 2\nline 3', 1)
+    end)
   end)
 
   describe('nvim_put', function()
@@ -455,6 +460,25 @@ describe('API', function()
       eq({0,1,2,0}, funcs.getpos('.'))
       eq('', nvim('eval', 'v:errmsg'))
     end)
+
+    it('detects charwise/linewise text (empty {type})', function()
+      -- linewise (final item is empty string)
+      nvim('put', {'line 1','line 2','line 3',''}, '', true, true)
+      expect([[
+
+        line 1
+        line 2
+        line 3]])
+      eq({0,4,1,0}, funcs.getpos('.'))
+      command('%delete _')
+      -- charwise (final item is non-empty)
+      nvim('put', {'line 1','line 2','line 3'}, '', true, true)
+      expect([[
+        line 1
+        line 2
+        line 3]])
+      eq({0,3,6,0}, funcs.getpos('.'))
+    end)
   end)
 
   describe('nvim_strwidth', function()
diff --git a/test/functional/terminal/tui_spec.lua b/test/functional/terminal/tui_spec.lua
index 08ff06e0a5..e7db39b5d0 100644
--- a/test/functional/terminal/tui_spec.lua
+++ b/test/functional/terminal/tui_spec.lua
@@ -324,6 +324,57 @@ describe('TUI', function()
     expect_cmdline('"stuff 1 more typed"')
   end)
 
+  it('paste: recovers from vim.paste() failure', function()
+    child_session:request('nvim_execute_lua', [[
+      _G.save_paste_fn = vim._paste
+      vim._paste = function(lines, phase) error("fake fail") end
+    ]], {})
+    -- Start pasting...
+    feed_data('\027[200~line 1\nline 2\n')
+    screen:expect{grid=[[
+                                                        |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:                                                  }|
+      {8:paste: Error executing lua: [string "<nvim>"]:2: f}|
+      {10:Press ENTER or type command to continue}{1: }          |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+    -- Remaining chunks are discarded after vim.paste() failure.
+    feed_data('line 3\nline 4\n')
+    feed_data('line 5\nline 6\n')
+    feed_data('line 7\nline 8\n')
+    -- Stop paste.
+    feed_data('\027[201~')
+    feed_data('\n')  -- <Enter>
+    -- Editor should still work after failed/drained paste.
+    feed_data('ityped input...\027\000')
+    screen:expect{grid=[[
+      typed input..{1:.}                                    |
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+    -- Paste works if vim.paste() succeeds.
+    child_session:request('nvim_execute_lua', [[
+      vim._paste = _G.save_paste_fn
+    ]], {})
+    feed_data('\027[200~line A\nline B\n\027[201~')
+    feed_data('\n')  -- <Enter>
+    screen:expect{grid=[[
+      typed input...line A                              |
+      line B                                            |
+      {1: }                                                 |
+      {4:~                                                 }|
+      {5:[No Name] [+]                                     }|
+                                                        |
+      {3:-- TERMINAL --}                                    |
+    ]]}
+  end)
+
   -- TODO
   it('paste: other modes', function()
     -- Other modes act like CTRL-C + paste.