lua: immediate-callback safe print()

2 files changed, 76 insertions, 39 deletions

diff --git a/src/nvim/lua/executor.c b/src/nvim/lua/executor.c
index 3fd1620845..44d56e770c 100644
--- a/src/nvim/lua/executor.c
+++ b/src/nvim/lua/executor.c
@@ -323,6 +323,42 @@ void executor_exec_lua(const String str, typval_T *const ret_tv)
   nlua_pop_typval(lstate, ret_tv);
 }
 
+static void nlua_print_event(void **argv)
+{
+  char *str = argv[0];
+  const size_t len = (size_t)(intptr_t)argv[1]-1;  // exclude final NUL
+
+  for (size_t i = 0; i < len;) {
+    const size_t start = i;
+    while (i < len) {
+      switch (str[i]) {
+        case NUL: {
+          str[i] = NL;
+          i++;
+          continue;
+        }
+        case NL: {
+          // TODO(bfredl): use proper multiline msg? Probably should implement
+          // print() in lua in terms of nvim_message(), when it is available.
+          str[i] = NUL;
+          i++;
+          break;
+        }
+        default: {
+          i++;
+          continue;
+        }
+      }
+      break;
+    }
+    msg((char_u *)str + start);
+  }
+  if (len && str[len - 1] == NUL) {  // Last was newline
+    msg((char_u *)"");
+  }
+  xfree(str);
+}
+
 /// Print as a Vim message
 ///
 /// @param  lstate  Lua interpreter state.
@@ -362,47 +398,24 @@ static int nlua_print(lua_State *const lstate)
     lua_pop(lstate, 1);
   }
 #undef PRINT_ERROR
-  lua_pop(lstate, nargs + 1);
   ga_append(&msg_ga, NUL);
-  {
-    const size_t len = (size_t)msg_ga.ga_len - 1;
-    char *const str = (char *)msg_ga.ga_data;
-
-    for (size_t i = 0; i < len;) {
-      const size_t start = i;
-      while (i < len) {
-        switch (str[i]) {
-          case NUL: {
-            str[i] = NL;
-            i++;
-            continue;
-          }
-          case NL: {
-            str[i] = NUL;
-            i++;
-            break;
-          }
-          default: {
-            i++;
-            continue;
-          }
-        }
-        break;
-      }
-      msg((char_u *)str + start);
-    }
-    if (len && str[len - 1] == NUL) {  // Last was newline
-      msg((char_u *)"");
-    }
+
+  if (in_fast_callback) {
+    multiqueue_put(main_loop.events, nlua_print_event,
+                   2, msg_ga.ga_data, msg_ga.ga_len);
+  } else {
+    nlua_print_event((void *[]){ msg_ga.ga_data,
+                                 (void *)(intptr_t)msg_ga.ga_len });
   }
-  ga_clear(&msg_ga);
   return 0;
+
 nlua_print_error:
-  emsgf(_("E5114: Error while converting print argument #%i: %.*s"),
-        curargidx, (int)errmsg_len, errmsg);
   ga_clear(&msg_ga);
-  lua_pop(lstate, lua_gettop(lstate));
-  return 0;
+  const char *fmt = _("E5114: Error while converting print argument #%i: %.*s");
+  size_t len = (size_t)vim_snprintf((char *)IObuff, IOSIZE, fmt, curargidx,
+                                    (int)errmsg_len, errmsg);
+  lua_pushlstring(lstate, (char *)IObuff, len);
+  return lua_error(lstate);
 }
 
 /// debug.debug: interaction with user while debugging.
diff --git a/test/functional/lua/overrides_spec.lua b/test/functional/lua/overrides_spec.lua
index 8f318e3503..c0541eeae9 100644
--- a/test/functional/lua/overrides_spec.lua
+++ b/test/functional/lua/overrides_spec.lua
@@ -14,6 +14,7 @@ local command = helpers.command
 local write_file = helpers.write_file
 local redir_exec = helpers.redir_exec
 local alter_slashes = helpers.alter_slashes
+local exec_lua = helpers.exec_lua
 
 local screen
 
@@ -53,11 +54,11 @@ describe('print', function()
       v_tblout = setmetatable({}, meta_tblout)
     ]])
     eq('', redir_exec('luafile ' .. fname))
-    eq('\nE5114: Error while converting print argument #2: [NULL]',
+    eq('\nE5105: Error while calling lua chunk: E5114: Error while converting print argument #2: [NULL]',
        redir_exec('lua print("foo", v_nilerr, "bar")'))
-    eq('\nE5114: Error while converting print argument #2: Xtest-functional-lua-overrides-luafile:2: abc',
+    eq('\nE5105: Error while calling lua chunk: E5114: Error while converting print argument #2: Xtest-functional-lua-overrides-luafile:2: abc',
        redir_exec('lua print("foo", v_abcerr, "bar")'))
-    eq('\nE5114: Error while converting print argument #2: <Unknown error: lua_tolstring returned NULL for tostring result>',
+    eq('\nE5105: Error while calling lua chunk: E5114: Error while converting print argument #2: <Unknown error: lua_tolstring returned NULL for tostring result>',
        redir_exec('lua print("foo", v_tblout, "bar")'))
   end)
   it('prints strings with NULs and NLs correctly', function()
@@ -76,6 +77,29 @@ describe('print', function()
     eq('\nabc ', redir_exec('lua print("abc", "")'))
     eq('\nabc  def', redir_exec('lua print("abc", "", "def")'))
   end)
+  it('defers printing in luv event handlers', function()
+    exec_lua([[
+      local cmd = ...
+      function test()
+        local timer = vim.loop.new_timer()
+        local done = false
+        timer:start(10, 0, function()
+          print("very fast")
+          timer:close()
+          done = true
+        end)
+        -- be kind to slow travis OS X jobs:
+        -- loop until we know for sure the callback has been executed
+        while not done do
+          os.execute(cmd)
+          vim.loop.run("nowait") -- fake os_breakcheck()
+        end
+        print("very slow")
+        vim.api.nvim_command("sleep 1m") -- force deferred event processing
+      end
+    ]], (iswin() and "timeout 1") or "sleep 0.1")
+    eq('\nvery slow\nvery fast',redir_exec('lua test()'))
+  end)
 end)
 
 describe('debug.debug', function()