feat(nvim_open_term): support input callback in lua

src/nvim/api/vim.c

@@ -1248,10 +1248,16 @@ fail:
 /// in a virtual terminal having the intended size.
 ///
 /// @param buffer the buffer to use (expected to be empty)
-/// @param opts   Optional parameters. Reserved for future use.
+/// @param opts   Optional parameters.
+///          - on_input: lua callback for input sent, i e keypresses in terminal
+///            mode. Note: keypresses are sent raw as they would be to the pty
+///            master end. For instance, a carriage return is sent
+///            as a "\r", not as a "\n". |textlock| applies. It is possible
+///            to call |nvim_chan_send| directly in the callback however.
+///                 ["input", term, bufnr, data]
 /// @param[out] err Error details, if any
 /// @return Channel id, or 0 on error
-Integer nvim_open_term(Buffer buffer, Dictionary opts, Error *err)
+Integer nvim_open_term(Buffer buffer, DictionaryOf(LuaRef) opts, Error *err)
   FUNC_API_SINCE(7)
 {
   buf_T *buf = find_buffer_by_handle(buffer, err);
@@ -1259,13 +1265,27 @@ Integer nvim_open_term(Buffer buffer, Dictionary opts, Error *err)
     return 0;
   }
 
-  if (opts.size > 0) {
+  LuaRef cb = LUA_NOREF;
-    api_set_error(err, kErrorTypeValidation, "opts dict isn't empty");
+  for (size_t i = 0; i < opts.size; i++) {
-    return 0;
+    String k = opts.items[i].key;
+    Object *v = &opts.items[i].value;
+    if (strequal("on_input", k.data)) {
+      if (v->type != kObjectTypeLuaRef) {
+        api_set_error(err, kErrorTypeValidation,
+                      "%s is not a function", "on_input");
+        return 0;
+      }
+      cb = v->data.luaref;
+      v->data.luaref = LUA_NOREF;
+      break;
+    } else {
+      api_set_error(err, kErrorTypeValidation, "unexpected key: %s", k.data);
+    }
   }
 
   TerminalOptions topts;
   Channel *chan = channel_alloc(kChannelStreamInternal);
+  chan->stream.internal.cb = cb;
   topts.data = chan;
   // NB: overridden in terminal_check_size if a window is already
   // displaying the buffer
@@ -1283,7 +1303,18 @@ Integer nvim_open_term(Buffer buffer, Dictionary opts, Error *err)
 
 static void term_write(char *buf, size_t size, void *data)
 {
-  // TODO(bfredl): lua callback
+  Channel *chan = data;
+  LuaRef cb = chan->stream.internal.cb;
+  if (cb == LUA_NOREF) {
+    return;
+  }
+  FIXED_TEMP_ARRAY(args, 3);
+  args.items[0] = INTEGER_OBJ((Integer)chan->id);
+  args.items[1] = BUFFER_OBJ(terminal_buf(chan->term));
+  args.items[2] = STRING_OBJ(((String){ .data = buf, .size = size }));
+  textlock++;
+  nlua_call_ref(cb, "input", args, false, NULL);
+  textlock--;
 }
 
 static void term_resize(uint16_t width, uint16_t height, void *data)

src/nvim/channel.c

@@ -8,6 +8,7 @@
 #include "nvim/eval/encode.h"
 #include "nvim/event/socket.h"
 #include "nvim/fileio.h"
+#include "nvim/lua/executor.h"
 #include "nvim/msgpack_rpc/channel.h"
 #include "nvim/msgpack_rpc/server.h"
 #include "nvim/os/shell.h"
@@ -136,6 +137,8 @@ bool channel_close(uint64_t id, ChannelPart part, const char **error)
       *error = (const char *)e_invstream;
       return false;
     }
+    api_free_luaref(chan->stream.internal.cb);
+    chan->stream.internal.cb = LUA_NOREF;
     break;
 
   default:
@@ -420,6 +423,7 @@ uint64_t channel_connect(bool tcp, const char *address, bool rpc, CallbackReader
       // Create a loopback channel. This avoids deadlock if nvim connects to
       // its own named pipe.
       channel = channel_alloc(kChannelStreamInternal);
+      channel->stream.internal.cb = LUA_NOREF;
       rpc_start(channel);
       goto end;
     }

src/nvim/channel.h

@@ -42,6 +42,10 @@ typedef struct {
   bool closed;
 } StderrState;
 
+typedef struct {
+  LuaRef cb;
+} InternalState;
+
 typedef struct {
   Callback cb;
   dict_T *self;
@@ -74,6 +78,7 @@ struct Channel {
     Stream socket;
     StdioPair stdio;
     StderrState err;
+    InternalState internal;
   } stream;
 
   bool is_rpc;

test/functional/api/vim_spec.lua

@@ -22,6 +22,7 @@ local source = helpers.source
 local next_msg = helpers.next_msg
 local tmpname = helpers.tmpname
 local write_file = helpers.write_file
+local exec_lua = helpers.exec_lua
 
 local pcall_err = helpers.pcall_err
 local format_string = helpers.format_string
@@ -2264,6 +2265,9 @@ describe('API', function()
         [2] = {background = tonumber('0xffff40'), bg_indexed = true};
         [3] = {background = Screen.colors.Plum1, fg_indexed = true, foreground = tonumber('0x00e000')};
         [4] = {bold = true, reverse = true, background = Screen.colors.Plum1};
+        [5] = {foreground = Screen.colors.Blue, background = Screen.colors.LightMagenta, bold = true};
+        [6] = {bold = true};
+        [7] = {reverse = true, background = Screen.colors.LightMagenta};
       })
     end)
 
@@ -2311,6 +2315,74 @@ describe('API', function()
                                                                                                             |
       ]]}
     end)
+
+    it('can handle input', function()
+      screen:try_resize(50, 10)
+      eq({3, 2}, exec_lua [[
+        buf = vim.api.nvim_create_buf(1,1)
+
+        stream = ''
+        do_the_echo = false
+        function input(_,t1,b1,data)
+          stream = stream .. data
+          _G.vals = {t1, b1}
+          if do_the_echo then
+            vim.api.nvim_chan_send(t1, data)
+          end
+        end
+
+        term = vim.api.nvim_open_term(buf, {on_input=input})
+        vim.api.nvim_open_win(buf, true, {width=40, height=5, row=1, col=1, relative='editor'})
+        return {term, buf}
+      ]])
+
+      screen:expect{grid=[[
+                                                          |
+        {0:~}{1:^                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~                                                 }|
+        {0:~                                                 }|
+        {0:~                                                 }|
+                                                          |
+      ]]}
+
+      feed 'iba<c-x>bla'
+      screen:expect{grid=[[
+                                                          |
+        {0:~}{7: }{1:                                       }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~                                                 }|
+        {0:~                                                 }|
+        {0:~                                                 }|
+        {6:-- TERMINAL --}                                    |
+      ]]}
+
+      eq('ba\024bla', exec_lua [[ return stream ]])
+      eq({3,2}, exec_lua [[ return vals ]])
+
+      exec_lua [[ do_the_echo = true ]]
+      feed 'herrejösses!'
+
+      screen:expect{grid=[[
+                                                          |
+        {0:~}{1:herrejösses!}{7: }{1:                           }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~}{1:                                        }{0:         }|
+        {0:~                                                 }|
+        {0:~                                                 }|
+        {0:~                                                 }|
+        {6:-- TERMINAL --}                                    |
+      ]]}
+      eq('ba\024blaherrejösses!', exec_lua [[ return stream ]])
+    end)
   end)
 
   describe('nvim_del_mark', function()