executor,functests: Add print() tests, some fixes

src/nvim/viml/executor/executor.c

@@ -384,9 +384,6 @@ static int nlua_print(lua_State *const lstate)
     lua_pushvalue(lstate, curargidx);  // arg
     if (lua_pcall(lstate, 1, 1, 0)) {
       errmsg = lua_tolstring(lstate, -1, &errmsg_len);
-      if (!errmsg) {
-        PRINT_ERROR("<Unknown error: lua_tolstring returned NULL for error>");
-      }
       goto nlua_print_error;
     }
     size_t len;
@@ -408,19 +405,32 @@ static int nlua_print(lua_State *const lstate)
     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 - 1;) {
+    for (size_t i = 0; i < len;) {
       const size_t start = i;
-      while (str[i] != NL && i < len - 1) {
-        if (str[i] == NUL) {
-          str[i] = NL;
+      while (i < len) {
+        switch (str[i]) {
+          case NUL: {
+            str[i] = NL;
+            i++;
+            continue;
+          }
+          case NL: {
+            str[i] = NUL;
+            i++;
+            break;
+          }
+          default: {
+            i++;
+            continue;
+          }
         }
-        i++;
-      }
-      if (str[i] == NL) {
-        str[i] = NUL;
+        break;
       }
       msg((char_u *)str + start);
     }
+    if (str[len - 1] == NUL) {  // Last was newline
+      msg((char_u *)"");
+    }
   }
   ga_clear(&msg_ga);
   return 0;

test/functional/lua/commands_spec.lua

@@ -46,6 +46,10 @@ describe(':lua command', function()
        exc_exec('lua vim.api.nvim_buf_set_lines(-10, 1, 1, false, {"TEST"})'))
     eq({''}, curbufmeths.get_lines(0, 100, false))
   end)
+  it('works with NULL errors', function()
+    eq([=[Vim(lua):E5105: Error while calling lua chunk: [NULL]]=],
+       exc_exec('lua error(nil)'))
+  end)
   it('accepts embedded NLs without heredoc', function()
     -- Such code is usually used for `:execute 'lua' {generated_string}`:
     -- heredocs do not work in this case.
@@ -106,6 +110,10 @@ describe(':luado command', function()
     eq([[Vim(luado):E5111: Error while calling lua function: [string "<VimL compiled string>"]:1: attempt to perform arithmetic on global 'liness' (a nil value)]],
        exc_exec('luado return liness + 1'))
   end)
+  it('works with NULL errors', function()
+    eq([=[Vim(luado):E5111: Error while calling lua function: [NULL]]=],
+       exc_exec('luado error(nil)'))
+  end)
   it('fails in sandbox when needed', function()
     curbufmeths.set_lines(0, 1, false, {"ABC", "def", "gHi"})
     eq('\nE48: Not allowed in sandbox: sandbox luado runs = (runs or 0) + 1',
@@ -148,4 +156,9 @@ describe(':luafile', function()
     eq(("Vim(luafile):E5113: Error while calling lua chunk: %s:1: attempt to index global 'vimm' (a nil value)"):format(fname),
        exc_exec('luafile ' .. fname))
   end)
+  it('works with NULL errors', function()
+    write_file(fname, 'error(nil)')
+    eq([=[Vim(luafile):E5113: Error while calling lua chunk: [NULL]]=],
+       exc_exec('luafile ' .. fname))
+  end)
 end)

test/functional/lua/luaeval_spec.lua

@@ -241,6 +241,8 @@ describe('luaeval()', function()
        exc_exec([[call luaeval("vim.xxx_nonexistent_key_xxx()")]]))
     eq('Vim(call):E5108: Error while calling lua chunk for luaeval(): [string "<VimL compiled string>"]:1: ERROR',
        exc_exec([[call luaeval("error('ERROR')")]]))
+    eq('Vim(call):E5108: Error while calling lua chunk for luaeval(): [NULL]',
+       exc_exec([[call luaeval("error(nil)")]]))
   end)
 
   it('does not leak memory when called with too long line',

test/functional/lua/overrides_spec.lua

@@ -0,0 +1,65 @@
+-- Test for Vim overrides of lua built-ins
+local helpers = require('test.functional.helpers')(after_each)
+
+local eq = helpers.eq
+local NIL = helpers.NIL
+local clear = helpers.clear
+local funcs = helpers.funcs
+local meths = helpers.meths
+local command = helpers.command
+local write_file = helpers.write_file
+local redir_exec = helpers.redir_exec
+
+local fname = 'Xtest-functional-lua-overrides-luafile'
+
+before_each(clear)
+
+after_each(function()
+  os.remove(fname)
+end)
+
+describe('print', function()
+  it('returns nothing', function()
+    eq(NIL, funcs.luaeval('print("abc")'))
+    eq(0, funcs.luaeval('select("#", print("abc"))'))
+  end)
+  it('allows catching printed text with :execute', function()
+    eq('\nabc', funcs.execute('lua print("abc")'))
+    eq('\nabc', funcs.execute('luado print("abc")'))
+    eq('\nabc', funcs.execute('call luaeval("print(\'abc\')")'))
+    write_file(fname, 'print("abc")')
+    eq('\nabc', funcs.execute('luafile ' .. fname))
+
+    eq('\nabc', redir_exec('lua print("abc")'))
+    eq('\nabc', redir_exec('luado print("abc")'))
+    eq('\nabc', redir_exec('call luaeval("print(\'abc\')")'))
+    write_file(fname, 'print("abc")')
+    eq('\nabc', redir_exec('luafile ' .. fname))
+  end)
+  it('handles errors in __tostring', function()
+    write_file(fname, [[
+      local meta_nilerr = { __tostring = function() error(nil) end }
+      local meta_abcerr = { __tostring = function() error("abc") end }
+      local meta_tblout = { __tostring = function() return {"TEST"} end }
+      v_nilerr = setmetatable({}, meta_nilerr)
+      v_abcerr = setmetatable({}, meta_abcerr)
+      v_tblout = setmetatable({}, meta_tblout)
+    ]])
+    eq('', redir_exec('luafile ' .. fname))
+    eq('\nE5114: 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',
+       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>',
+       redir_exec('lua print("foo", v_tblout, "bar")'))
+  end)
+  it('prints strings with NULs and NLs correctly', function()
+    meths.set_option('more', true)
+    eq('\nabc ^@ def\nghi^@^@^@jkl\nTEST\n\n\nT\n',
+       redir_exec([[lua print("abc \0 def\nghi\0\0\0jkl\nTEST\n\n\nT\n")]]))
+    eq('\nabc ^@ def\nghi^@^@^@jkl\nTEST\n\n\nT^@',
+       redir_exec([[lua print("abc \0 def\nghi\0\0\0jkl\nTEST\n\n\nT\0")]]))
+    eq('\nT^@', redir_exec([[lua print("T\0")]]))
+    eq('\nT\n', redir_exec([[lua print("T\n")]]))
+  end)
+end)