Merge pull request #20941 from zeertzjq/vim-8.2.1183

vim-patch:8.2.{partial:1183,1184,1199,1479,1484,1631,1632}: assert_fails() patches

41 files changed, 275 insertions, 126 deletions

diff --git a/runtime/doc/testing.txt b/runtime/doc/testing.txt
index f4375c3363..56e0dad656 100644
--- a/runtime/doc/testing.txt
+++ b/runtime/doc/testing.txt
@@ -98,18 +98,46 @@ assert_exception({error} [, {msg}])			*assert_exception()*
 			catch
 			  call assert_exception('E492:')
 			endtry
-
-assert_fails({cmd} [, {error} [, {msg}]])			*assert_fails()*
+<
+							*assert_fails()*
+assert_fails({cmd} [, {error} [, {msg} [, {lnum} [, {context}]]]])
 		Run {cmd} and add an error message to |v:errors| if it does
-		NOT produce an error.  Also see |assert-return|.
-		When {error} is given it must match in |v:errmsg|.
+		NOT produce an error or when {error} is not found in the
+		error message.  Also see |assert-return|.
+
+		When {error} is a string it must be found literally in the
+		first reported error. Most often this will be the error code,
+		including the colon, e.g. "E123:". >
+			assert_fails('bad cmd', 'E987:')
+<
+		When {error} is a |List| with one or two strings, these are
+		used as patterns.  The first pattern is matched against the
+		first reported error: >
+			assert_fails('cmd', ['E987:.*expected bool'])
+<		The second pattern, if present, is matched against the last
+		reported error.  To only match the last error use an empty
+		string for the first error: >
+			assert_fails('cmd', ['', 'E987:'])
+<
+		If {msg} is empty then it is not used.  Do this to get the
+		default message when passing the {lnum} argument.
+
+		When {lnum} is present and not negative, and the {error}
+		argument is present and matches, then this is compared with
+		the line number at which the error was reported. That can be
+		the line number in a function or in a script.
+
+		When {context} is present it is used as a pattern and matched
+		against the context (script name or function name) where
+		{lnum} is located in.
+
 		Note that beeping is not considered an error, and some failing
 		commands only beep.  Use |assert_beeps()| for those.
 
 		Can also be used as a |method|: >
 			GetCmd()->assert_fails('E99:')
 
-assert_false({actual} [, {msg}])				*assert_false()*
+assert_false({actual} [, {msg}])			*assert_false()*
 		When {actual} is not false an error message is added to
 		|v:errors|, like with |assert_equal()|.
 		Also see |assert-return|.
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 37da475e59..5b8cbcfbb3 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -545,7 +545,7 @@ int var_redir_start(char *name, int append)
 
   // check if we can write to the variable: set it to or append an empty
   // string
-  int save_emsg = did_emsg;
+  const int called_emsg_before = called_emsg;
   did_emsg = false;
   typval_T tv;
   tv.v_type = VAR_STRING;
@@ -556,9 +556,7 @@ int var_redir_start(char *name, int append)
     set_var_lval(redir_lval, redir_endp, &tv, true, false, "=");
   }
   clear_lval(redir_lval);
-  int err = did_emsg;
-  did_emsg |= save_emsg;
-  if (err) {
+  if (called_emsg > called_emsg_before) {
     redir_endp = NULL;      // don't store a value, only cleanup
     var_redir_stop();
     return FAIL;
@@ -2185,7 +2183,7 @@ char *get_user_var_name(expand_T *xp, int idx)
 /// Does not use 'cpo' and always uses 'magic'.
 ///
 /// @return  true if "pat" matches "text".
-int pattern_match(char *pat, char *text, bool ic)
+int pattern_match(const char *pat, const char *text, bool ic)
 {
   int matches = 0;
   regmatch_T regmatch;
@@ -2193,7 +2191,7 @@ int pattern_match(char *pat, char *text, bool ic)
   // avoid 'l' flag in 'cpoptions'
   char *save_cpo = p_cpo;
   p_cpo = empty_option;
-  regmatch.regprog = vim_regcomp(pat, RE_MAGIC + RE_STRING);
+  regmatch.regprog = vim_regcomp((char *)pat, RE_MAGIC + RE_STRING);
   if (regmatch.regprog != NULL) {
     regmatch.rm_ic = ic;
     matches = vim_regexec_nl(&regmatch, (char_u *)text, (colnr_T)0);
@@ -8881,7 +8879,7 @@ int typval_compare(typval_T *typ1, typval_T *typ2, exprtype_T type, bool ic)
 
     case EXPR_MATCH:
     case EXPR_NOMATCH:
-      n1 = pattern_match((char *)s2, (char *)s1, ic);
+      n1 = pattern_match(s2, s1, ic);
       if (type == EXPR_NOMATCH) {
         n1 = !n1;
       }
diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index ecb411a652..61e7f99afd 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -38,7 +38,7 @@ return {
     assert_equal={args={2, 3}, base=2},
     assert_equalfile={args={2, 3}, base=1},
     assert_exception={args={1, 2}},
-    assert_fails={args={1, 3}, base=1},
+    assert_fails={args={1, 5}, base=1},
     assert_false={args={1, 2}, base=1},
     assert_inrange={args={3, 4}, base=3},
     assert_match={args={2, 3}, base=2},
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index c556aac1fd..14266fc859 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -194,6 +194,12 @@ EXTERN int emsg_skip INIT(= 0);             // don't display errors for
                                             // expression that is skipped
 EXTERN bool emsg_severe INIT(= false);      // use message of next of several
                                             //  emsg() calls for throw
+// used by assert_fails()
+EXTERN bool emsg_assert_fails_used INIT(= false);
+EXTERN char *emsg_assert_fails_msg INIT(= NULL);
+EXTERN long emsg_assert_fails_lnum INIT(= 0);
+EXTERN char *emsg_assert_fails_context INIT(= NULL);
+
 EXTERN bool did_endif INIT(= false);        // just had ":endif"
 EXTERN dict_T vimvardict;                   // Dictionary with v: variables
 EXTERN dict_T globvardict;                  // Dictionary with g: variables
diff --git a/src/nvim/message.c b/src/nvim/message.c
index b608b59c9b..fa1c8036e6 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -663,6 +663,13 @@ static bool emsg_multiline(const char *s, bool multiline)
       return true;
     }
 
+    if (emsg_assert_fails_used && emsg_assert_fails_msg == NULL) {
+      emsg_assert_fails_msg = xstrdup(s);
+      emsg_assert_fails_lnum = SOURCING_LNUM;
+      xfree(emsg_assert_fails_context);
+      emsg_assert_fails_context = xstrdup(SOURCING_NAME == NULL ? "" : SOURCING_NAME);
+    }
+
     // set "v:errmsg", also when using ":silent! cmd"
     set_vim_var_string(VV_ERRMSG, s, -1);
 
diff --git a/src/nvim/testdir/test_assert.vim b/src/nvim/testdir/test_assert.vim
index 8723a0a38d..431908e95c 100644
--- a/src/nvim/testdir/test_assert.vim
+++ b/src/nvim/testdir/test_assert.vim
@@ -48,6 +48,11 @@ func Test_assert_equal()
   call assert_equal('XxxxxxxxxxxxxxxxxxxxxxX', 'XyyyyyyyyyyyyyyyyyyyyyyyyyX')
   call assert_match("Expected 'X\\\\\\[x occurs 21 times]X' but got 'X\\\\\\[y occurs 25 times]X'", v:errors[0])
   call remove(v:errors, 0)
+
+  " special characters are escaped
+  call assert_equal("\b\e\f\n\t\r\\\x01\x7f", 'x')
+  call assert_match('Expected ''\\b\\e\\f\\n\\t\\r\\\\\\x01\\x7f'' but got ''x''', v:errors[0])
+  call remove(v:errors, 0)
 endfunc
 
 func Test_assert_equal_dict()
@@ -146,6 +151,14 @@ func Test_assert_exception()
   try
     nocommand
   catch
+    call assert_equal(1, assert_exception('E12345:'))
+  endtry
+  call assert_match("Expected 'E12345:' but got 'Vim:E492: ", v:errors[0])
+  call remove(v:errors, 0)
+
+  try
+    nocommand
+  catch
     try
       " illegal argument, get NULL for error
       call assert_equal(1, assert_exception([]))
@@ -153,6 +166,10 @@ func Test_assert_exception()
       call assert_equal(0, assert_exception('E730:'))
     endtry
   endtry
+
+  call assert_equal(1, assert_exception('E492:'))
+  call assert_match('v:exception is not set', v:errors[0])
+  call remove(v:errors, 0)
 endfunc
 
 func Test_wrong_error_type()
@@ -202,6 +219,14 @@ func Test_assert_fail_fails()
   call assert_match("stupid: Expected 'E9876' but got 'E492:", v:errors[0])
   call remove(v:errors, 0)
 
+  call assert_equal(1, assert_fails('xxx', ['E9876']))
+  call assert_match("Expected \\['E9876'\\] but got 'E492:", v:errors[0])
+  call remove(v:errors, 0)
+
+  call assert_equal(1, assert_fails('xxx', ['E492:', 'E9876']))
+  call assert_match("Expected \\['E492:', 'E9876'\\] but got 'E492:", v:errors[0])
+  call remove(v:errors, 0)
+
   call assert_equal(1, assert_fails('echo', '', 'echo command'))
   call assert_match("command did not fail: echo command", v:errors[0])
   call remove(v:errors, 0)
@@ -209,6 +234,41 @@ func Test_assert_fail_fails()
   call assert_equal(1, 'echo'->assert_fails('', 'echo command'))
   call assert_match("command did not fail: echo command", v:errors[0])
   call remove(v:errors, 0)
+
+  try
+    call assert_equal(1, assert_fails('xxx', []))
+  catch
+    let exp = v:exception
+  endtry
+  call assert_match("E856: assert_fails() second argument", exp)
+
+  try
+    call assert_equal(1, assert_fails('xxx', ['1', '2', '3']))
+  catch
+    let exp = v:exception
+  endtry
+  call assert_match("E856: assert_fails() second argument", exp)
+
+  try
+    call assert_equal(1, assert_fails('xxx', #{one: 1}))
+  catch
+    let exp = v:exception
+  endtry
+  call assert_match("E856: assert_fails() second argument", exp)
+
+  try
+    call assert_equal(1, assert_fails('xxx', 'E492', '', 'burp'))
+  catch
+    let exp = v:exception
+  endtry
+  call assert_match("E1115: assert_fails() fourth argument must be a number", exp)
+
+  try
+    call assert_equal(1, assert_fails('xxx', 'E492', '', 54, 123))
+  catch
+    let exp = v:exception
+  endtry
+  call assert_match("E1116: assert_fails() fifth argument must be a string", exp)
 endfunc
 
 func Test_assert_fails_in_try_block()
diff --git a/src/nvim/testdir/test_autochdir.vim b/src/nvim/testdir/test_autochdir.vim
index 4229095f9f..a8810047a0 100644
--- a/src/nvim/testdir/test_autochdir.vim
+++ b/src/nvim/testdir/test_autochdir.vim
@@ -122,9 +122,7 @@ endfunc
 func Test_multibyte()
   " using an invalid character should not cause a crash
   set wic
-  " Except on Windows, E472 is also thrown last, but v8.1.1183 isn't ported yet
-  " call assert_fails('tc �����*', has('win32') ? 'E480:' : 'E344:')
-  call assert_fails('tc �����*', has('win32') ? 'E480:' : 'E472:')
+  call assert_fails('tc �����*', has('win32') ? 'E480:' : 'E344:')
   set nowic
 endfunc
 
diff --git a/src/nvim/testdir/test_autocmd.vim b/src/nvim/testdir/test_autocmd.vim
index a3534cea87..50904bab34 100644
--- a/src/nvim/testdir/test_autocmd.vim
+++ b/src/nvim/testdir/test_autocmd.vim
@@ -175,9 +175,7 @@ func Test_autocmd_bufunload_avoiding_SEGV_01()
     exe 'autocmd BufUnload <buffer> ' . (lastbuf + 1) . 'bwipeout!'
   augroup END
 
-  " Todo: check for E937 generated first
-  " call assert_fails('edit bb.txt', 'E937:')
-  call assert_fails('edit bb.txt', 'E517:')
+  call assert_fails('edit bb.txt', ['E937:', 'E517:'])
 
   autocmd! test_autocmd_bufunload
   augroup! test_autocmd_bufunload
@@ -2933,7 +2931,7 @@ func Test_BufDelete_changebuf()
   augroup END
   let save_cpo = &cpo
   set cpo+=f
-  call assert_fails('r Xfile', 'E484:')
+  call assert_fails('r Xfile', ['E812:', 'E484:'])
   call assert_equal('somefile', @%)
   let &cpo = save_cpo
   augroup TestAuCmd
diff --git a/src/nvim/testdir/test_buffer.vim b/src/nvim/testdir/test_buffer.vim
index 4def3b5df9..27c2d5d442 100644
--- a/src/nvim/testdir/test_buffer.vim
+++ b/src/nvim/testdir/test_buffer.vim
@@ -76,7 +76,7 @@ func Test_bunload_with_offset()
     let caught_E90 = 1
   endtry
   call assert_equal(1, caught_E90)
-  call assert_fails('$bunload', 'E515:')
+  call assert_fails('$bunload', 'E90:')
 endfunc
 
 " Test for :buffer, :bnext, :bprevious, :brewind, :blast and :bmodified
@@ -282,7 +282,7 @@ func Test_goto_buf_with_confirm()
   call assert_equal(1, &modified)
   call assert_equal('', @%)
   call feedkeys('y', 'L')
-  call assert_fails('confirm b Xfile', 'E37:')
+  call assert_fails('confirm b Xfile', ['', 'E37:'])
   call assert_equal(1, &modified)
   call assert_equal('', @%)
   call feedkeys('n', 'L')
diff --git a/src/nvim/testdir/test_cd.vim b/src/nvim/testdir/test_cd.vim
index 43c4e09d40..2a2437f542 100644
--- a/src/nvim/testdir/test_cd.vim
+++ b/src/nvim/testdir/test_cd.vim
@@ -5,7 +5,7 @@ source check.vim
 
 func Test_cd_large_path()
   " This used to crash with a heap write overflow.
-  call assert_fails('cd ' . repeat('x', 5000), 'E472:')
+  call assert_fails('cd ' . repeat('x', 5000), 'E344:')
 endfunc
 
 func Test_cd_up_and_down()
@@ -45,9 +45,7 @@ func Test_cd_minus()
   call assert_equal(path, getcwd())
 
   " Test for :cd - after a failed :cd
-  " v8.2.1183 is not ported yet
-  " call assert_fails('cd /nonexistent', 'E344:')
-  call assert_fails('cd /nonexistent', 'E472:')
+  call assert_fails('cd /nonexistent', 'E344:')
   call assert_equal(path, getcwd())
   cd -
   call assert_equal(path_dotdot, getcwd())
@@ -103,7 +101,7 @@ func Test_chdir_func()
   call assert_equal('testdir', fnamemodify(getcwd(1, 1), ':t'))
 
   " Error case
-  call assert_fails("call chdir('dir-abcd')", 'E472:')
+  call assert_fails("call chdir('dir-abcd')", 'E344:')
   silent! let d = chdir("dir_abcd")
   call assert_equal("", d)
   " Should not crash
diff --git a/src/nvim/testdir/test_clientserver.vim b/src/nvim/testdir/test_clientserver.vim
index 301dad8341..19a92dce3c 100644
--- a/src/nvim/testdir/test_clientserver.vim
+++ b/src/nvim/testdir/test_clientserver.vim
@@ -102,7 +102,7 @@ func Test_client_server()
   call remote_send(v:servername, ":let g:testvar2 = 75\<CR>")
   call feedkeys('', 'x')
   call assert_equal(75, g:testvar2)
-  call assert_fails('let v = remote_expr(v:servername, "/2")', 'E449:')
+  call assert_fails('let v = remote_expr(v:servername, "/2")', ['E15:.*/2'])
 
   call remote_send(name, ":call server2client(expand('<client>'), 'got it')\<CR>", 'g:myserverid')
   call assert_equal('got it', g:myserverid->remote_read(2))
@@ -184,8 +184,8 @@ func Test_client_server()
 
   call assert_fails('call remote_startserver([])', 'E730:')
   call assert_fails("let x = remote_peek([])", 'E730:')
-  call assert_fails("let x = remote_read('vim10')", 'E277:')
-  call assert_fails("call server2client('abc', 'xyz')", 'E258:')
+  call assert_fails("let x = remote_read('vim10')", ['E573:.*vim10'])
+  call assert_fails("call server2client('abc', 'xyz')", ['E573:.*abc'])
 endfunc
 
 " Uncomment this line to get a debugging log
diff --git a/src/nvim/testdir/test_cmdline.vim b/src/nvim/testdir/test_cmdline.vim
index 3e5fe06c90..c00172ed68 100644
--- a/src/nvim/testdir/test_cmdline.vim
+++ b/src/nvim/testdir/test_cmdline.vim
@@ -1154,7 +1154,7 @@ func Test_cmdline_search_range()
   call assert_equal('B', getline(2))
 
   let @/ = 'apple'
-  call assert_fails('\/print', 'E486:')
+  call assert_fails('\/print', ['E486:.*apple'])
 
   bwipe!
 endfunc
@@ -1272,7 +1272,7 @@ func Test_verbosefile()
   call delete('Xlog')
   call mkdir('Xdir')
   if !has('win32')  " FIXME: no error on Windows, libuv bug?
-  call assert_fails('set verbosefile=Xdir', 'E474:')
+  call assert_fails('set verbosefile=Xdir', ['E484:.*Xdir', 'E474:'])
   endif
   call delete('Xdir', 'd')
 endfunc
@@ -1525,7 +1525,7 @@ func Test_cmdwin_jump_to_win()
   call assert_fails('call feedkeys("q:\<C-W>\<C-W>\<CR>", "xt")', 'E11:')
   new
   set modified
-  call assert_fails('call feedkeys("q/:qall\<CR>", "xt")', 'E162:')
+  call assert_fails('call feedkeys("q/:qall\<CR>", "xt")', ['E37:', 'E162:'])
   close!
   call feedkeys("q/:close\<CR>", "xt")
   call assert_equal(1, winnr('$'))
@@ -1539,13 +1539,7 @@ endfunc
 
 func Test_cmdwin_tabpage()
   tabedit
-  " v8.2.1919 isn't ported yet, so E492 is thrown after E11 here.
-  " v8.2.1183 also isn't ported yet, so we also can't assert E11 directly.
-  " For now, assert E11 and E492 separately. When v8.2.1183 is ported, the
-  " assert for E492 will fail and this workaround should be removed.
-  " call assert_fails("silent norm q/g	:I\<Esc>", 'E11:')
-  call assert_fails("silent norm q/g	", 'E11:')
-  call assert_fails("silent norm q/g	:I\<Esc>", 'E492:')
+  call assert_fails("silent norm q/g	:I\<Esc>", 'E11:')
   tabclose!
 endfunc
 
diff --git a/src/nvim/testdir/test_cpoptions.vim b/src/nvim/testdir/test_cpoptions.vim
index 76d2c9542d..ef51d955f1 100644
--- a/src/nvim/testdir/test_cpoptions.vim
+++ b/src/nvim/testdir/test_cpoptions.vim
@@ -104,7 +104,7 @@ func Test_cpo_C()
   source Xfile
   call assert_equal([1, 2], g:l)
   set cpo+=C
-  call assert_fails('source Xfile', 'E10:')
+  call assert_fails('source Xfile', ['E697:', 'E10:'])
   call delete('Xfile')
   let &cpo = save_cpo
 endfunc
diff --git a/src/nvim/testdir/test_eval_stuff.vim b/src/nvim/testdir/test_eval_stuff.vim
index 851048ec5b..46482c34a1 100644
--- a/src/nvim/testdir/test_eval_stuff.vim
+++ b/src/nvim/testdir/test_eval_stuff.vim
@@ -20,13 +20,8 @@ func Test_nocatch_restore_silent_emsg()
     throw 1
   catch
   endtry
-  echoerr 'wrong'
-  let c1 = nr2char(screenchar(&lines, 1))
-  let c2 = nr2char(screenchar(&lines, 2))
-  let c3 = nr2char(screenchar(&lines, 3))
-  let c4 = nr2char(screenchar(&lines, 4))
-  let c5 = nr2char(screenchar(&lines, 5))
-  call assert_equal('wrong', c1 . c2 . c3 . c4 . c5)
+  echoerr 'wrong again'
+  call assert_equal('wrong again', ScreenLine(&lines))
 endfunc
 
 func Test_mkdir_p()
diff --git a/src/nvim/testdir/test_excmd.vim b/src/nvim/testdir/test_excmd.vim
index 04ab8e288f..582dcaac2c 100644
--- a/src/nvim/testdir/test_excmd.vim
+++ b/src/nvim/testdir/test_excmd.vim
@@ -481,8 +481,8 @@ func Test_redir_cmd()
   call assert_fails('redir abc', 'E475:')
   call assert_fails('redir => 1abc', 'E474:')
   call assert_fails('redir => a b', 'E488:')
-  call assert_fails('redir => abc[1]', 'E475:')
-  let b=0zFF
+  call assert_fails('redir => abc[1]', 'E121:')
+  let b = 0zFF
   call assert_fails('redir =>> b', 'E734:')
   unlet b
 
diff --git a/src/nvim/testdir/test_expr.vim b/src/nvim/testdir/test_expr.vim
index 0579ce7dcb..ea874cc398 100644
--- a/src/nvim/testdir/test_expr.vim
+++ b/src/nvim/testdir/test_expr.vim
@@ -528,7 +528,7 @@ func Test_setmatches()
   endif
   eval set->setmatches()
   call assert_equal(exp, getmatches())
-  call assert_fails('let m = setmatches([], [])', 'E957:')
+  call assert_fails('let m = setmatches([], [])', 'E745:')
 endfunc
 
 func Test_empty_concatenate()
diff --git a/src/nvim/testdir/test_functions.vim b/src/nvim/testdir/test_functions.vim
index 1ba0cf9080..06c995db86 100644
--- a/src/nvim/testdir/test_functions.vim
+++ b/src/nvim/testdir/test_functions.vim
@@ -211,7 +211,7 @@ func Test_str2nr()
   if has('float')
     call assert_fails('call str2nr(1.2)', 'E806:')
   endif
-  call assert_fails('call str2nr(10, [])', 'E474:')
+  call assert_fails('call str2nr(10, [])', 'E745:')
 endfunc
 
 func Test_strftime()
@@ -1728,11 +1728,11 @@ func Test_libcall_libcallnr()
   call assert_equal(4, 'abcd'->libcallnr(libc, 'strlen'))
   call assert_equal(char2nr('A'), char2nr('a')->libcallnr(libc, 'toupper'))
 
-  call assert_fails("call libcall(libc, 'Xdoesnotexist_', '')", 'E364:')
-  call assert_fails("call libcallnr(libc, 'Xdoesnotexist_', '')", 'E364:')
+  call assert_fails("call libcall(libc, 'Xdoesnotexist_', '')", ['', 'E364:'])
+  call assert_fails("call libcallnr(libc, 'Xdoesnotexist_', '')", ['', 'E364:'])
 
-  call assert_fails("call libcall('Xdoesnotexist_', 'getenv', 'HOME')", 'E364:')
-  call assert_fails("call libcallnr('Xdoesnotexist_', 'strlen', 'abcd')", 'E364:')
+  call assert_fails("call libcall('Xdoesnotexist_', 'getenv', 'HOME')", ['', 'E364:'])
+  call assert_fails("call libcallnr('Xdoesnotexist_', 'strlen', 'abcd')", ['', 'E364:'])
 endfunc
 
 sandbox function Fsandbox()
diff --git a/src/nvim/testdir/test_global.vim b/src/nvim/testdir/test_global.vim
index cb6851250c..bbfe374f51 100644
--- a/src/nvim/testdir/test_global.vim
+++ b/src/nvim/testdir/test_global.vim
@@ -39,7 +39,7 @@ endfunc
 func Test_global_error()
   call assert_fails('g\\a', 'E10:')
   call assert_fails('g', 'E148:')
-  call assert_fails('g/\(/y', 'E476:')
+  call assert_fails('g/\(/y', 'E54:')
 endfunc
 
 " Test for printing lines using :g with different search patterns
diff --git a/src/nvim/testdir/test_let.vim b/src/nvim/testdir/test_let.vim
index 937076aa2a..f05e06f774 100644
--- a/src/nvim/testdir/test_let.vim
+++ b/src/nvim/testdir/test_let.vim
@@ -262,7 +262,7 @@ func Test_let_errors()
   let l = [1, 2, 3]
   call assert_fails('let l[:] = 5', 'E709:')
 
-  call assert_fails('let x:lnum=5', 'E488:')
+  call assert_fails('let x:lnum=5', ['E121:', 'E488:'])
   call assert_fails('let v:=5', 'E461:')
   call assert_fails('let [a]', 'E474:')
   call assert_fails('let [a, b] = [', 'E697:')
diff --git a/src/nvim/testdir/test_listdict.vim b/src/nvim/testdir/test_listdict.vim
index 1ecdcd2157..7cb48876e8 100644
--- a/src/nvim/testdir/test_listdict.vim
+++ b/src/nvim/testdir/test_listdict.vim
@@ -680,10 +680,10 @@ func Test_reverse_sort_uniq()
   endif
 
   call assert_fails('call reverse("")', 'E899:')
-  call assert_fails('call uniq([1, 2], {x, y -> []})', 'E882:')
+  call assert_fails('call uniq([1, 2], {x, y -> []})', 'E745:')
   call assert_fails("call sort([1, 2], function('min'), 1)", "E715:")
   call assert_fails("call sort([1, 2], function('invalid_func'))", "E700:")
-  call assert_fails("call sort([1, 2], function('min'))", "E702:")
+  call assert_fails("call sort([1, 2], function('min'))", "E118:")
 endfunc
 
 " reduce a list or a blob
@@ -983,7 +983,7 @@ func Test_listdict_index()
   call assert_fails('echo d[1:2]', 'E719:')
   call assert_fails("let v = [4, 6][{-> 1}]", 'E729:')
   call assert_fails("let v = range(5)[2:[]]", 'E730:')
-  call assert_fails("let v = range(5)[2:{-> 2}(]", 'E116:')
+  call assert_fails("let v = range(5)[2:{-> 2}(]", ['E15:', 'E116:'])
   call assert_fails("let v = range(5)[2:3", 'E111:')
   call assert_fails("let l = insert([1,2,3], 4, 10)", 'E684:')
   call assert_fails("let l = insert([1,2,3], 4, -10)", 'E684:')
diff --git a/src/nvim/testdir/test_match.vim b/src/nvim/testdir/test_match.vim
index 29d087bc23..5d9be99444 100644
--- a/src/nvim/testdir/test_match.vim
+++ b/src/nvim/testdir/test_match.vim
@@ -163,7 +163,7 @@ func Test_matchadd_error()
   " call assert_fails("call matchadd('GroupDoesNotExist', 'X')", 'E28:')
   call matchadd('GroupDoesNotExist', 'X')
   call assert_equal([{'group': 'GroupDoesNotExist', 'pattern': 'X', 'priority': 10, 'id': 1206}], getmatches())
-  call assert_fails("call matchadd('Search', '\\(')", 'E475:')
+  call assert_fails("call matchadd('Search', '\\(')", 'E54:')
   call assert_fails("call matchadd('Search', 'XXX', 1, 123, 1)", 'E715:')
   call assert_fails("call matchadd('Error', 'XXX', 1, 3)", 'E798:')
   call assert_fails("call matchadd('Error', 'XXX', 1, 0)", 'E799:')
diff --git a/src/nvim/testdir/test_matchfuzzy.vim b/src/nvim/testdir/test_matchfuzzy.vim
index c836bc87aa..b46550fbc3 100644
--- a/src/nvim/testdir/test_matchfuzzy.vim
+++ b/src/nvim/testdir/test_matchfuzzy.vim
@@ -6,9 +6,7 @@ source check.vim
 " Test for matchfuzzy()
 func Test_matchfuzzy()
   call assert_fails('call matchfuzzy(10, "abc")', 'E686:')
-  " Needs v8.2.1183; match the final error that's thrown for now
-  " call assert_fails('call matchfuzzy(["abc"], [])', 'E730:')
-  call assert_fails('call matchfuzzy(["abc"], [])', 'E475:')
+  call assert_fails('call matchfuzzy(["abc"], [])', 'E730:')
   call assert_fails("let x = matchfuzzy(v:_null_list, 'foo')", 'E686:')
   call assert_fails('call matchfuzzy(["abc"], v:_null_string)', 'E475:')
   call assert_equal([], matchfuzzy([], 'abc'))
@@ -75,12 +73,9 @@ func Test_matchfuzzy()
   call assert_fails("let x = matchfuzzy(l, 'day', {'text_cb' : {a, b -> 1}})", 'E119:')
   call assert_equal([], matchfuzzy(l, 'cam'))
   " Nvim's callback implementation is different, so E6000 is expected instead,
-  " but we need v8.2.1183 to assert it
   " call assert_fails("let x = matchfuzzy(l, 'cam', {'text_cb' : []})", 'E921:')
-  " call assert_fails("let x = matchfuzzy(l, 'cam', {'text_cb' : []})", 'E6000:')
-  call assert_fails("let x = matchfuzzy(l, 'cam', {'text_cb' : []})", 'E475:')
-  " call assert_fails("let x = matchfuzzy(l, 'foo', {'key' : []})", 'E730:')
-  call assert_fails("let x = matchfuzzy(l, 'foo', {'key' : []})", 'E475:')
+  call assert_fails("let x = matchfuzzy(l, 'cam', {'text_cb' : []})", 'E6000:')
+  call assert_fails("let x = matchfuzzy(l, 'foo', {'key' : []})", 'E730:')
   call assert_fails("let x = matchfuzzy(l, 'cam', v:_null_dict)", 'E715:')
   call assert_fails("let x = matchfuzzy(l, 'foo', {'key' : v:_null_string})", 'E475:')
   " Nvim doesn't have null functions
@@ -155,12 +150,9 @@ func Test_matchfuzzypos()
   call assert_fails("let x = matchfuzzypos(l, 'day', {'text_cb' : {a, b -> 1}})", 'E119:')
   call assert_equal([[], [], []], matchfuzzypos(l, 'cam'))
   " Nvim's callback implementation is different, so E6000 is expected instead,
-  " but we need v8.2.1183 to assert it
   " call assert_fails("let x = matchfuzzypos(l, 'cam', {'text_cb' : []})", 'E921:')
-  " call assert_fails("let x = matchfuzzypos(l, 'cam', {'text_cb' : []})", 'E6000:')
-  call assert_fails("let x = matchfuzzypos(l, 'cam', {'text_cb' : []})", 'E475:')
-  " call assert_fails("let x = matchfuzzypos(l, 'foo', {'key' : []})", 'E730:')
-  call assert_fails("let x = matchfuzzypos(l, 'foo', {'key' : []})", 'E475:')
+  call assert_fails("let x = matchfuzzypos(l, 'cam', {'text_cb' : []})", 'E6000:')
+  call assert_fails("let x = matchfuzzypos(l, 'foo', {'key' : []})", 'E730:')
   call assert_fails("let x = matchfuzzypos(l, 'cam', v:_null_dict)", 'E715:')
   call assert_fails("let x = matchfuzzypos(l, 'foo', {'key' : v:_null_string})", 'E475:')
   " Nvim doesn't have null functions
diff --git a/src/nvim/testdir/test_menu.vim b/src/nvim/testdir/test_menu.vim
index 58da0ed382..a1121632e6 100644
--- a/src/nvim/testdir/test_menu.vim
+++ b/src/nvim/testdir/test_menu.vim
@@ -153,7 +153,7 @@ func Test_menu_errors()
   call assert_fails('menu Test.Foo.Bar', 'E327:')
   call assert_fails('cmenu Test.Foo', 'E328:')
   call assert_fails('emenu x Test.Foo', 'E475:')
-  call assert_fails('emenu Test.Foo.Bar', 'E334:')
+  call assert_fails('emenu Test.Foo.Bar', 'E327:')
   call assert_fails('menutranslate Test', 'E474:')
 
   silent! unmenu Foo
diff --git a/src/nvim/testdir/test_method.vim b/src/nvim/testdir/test_method.vim
index e035b3ef50..057f4a1bea 100644
--- a/src/nvim/testdir/test_method.vim
+++ b/src/nvim/testdir/test_method.vim
@@ -131,9 +131,9 @@ func Test_method_syntax()
   eval [1, 2, 3]  
 	\ ->sort(
 	\ )
-  call assert_fails('eval [1, 2, 3]-> sort()', 'E260:')
+  call assert_fails('eval [1, 2, 3]-> sort()', 'E15:')
   call assert_fails('eval [1, 2, 3]->sort ()', 'E274:')
-  call assert_fails('eval [1, 2, 3]-> sort ()', 'E260:')
+  call assert_fails('eval [1, 2, 3]-> sort ()', 'E15:')
 endfunc
 
 func Test_method_lambda()
diff --git a/src/nvim/testdir/test_normal.vim b/src/nvim/testdir/test_normal.vim
index 5fc670e422..84929e2be3 100644
--- a/src/nvim/testdir/test_normal.vim
+++ b/src/nvim/testdir/test_normal.vim
@@ -1650,7 +1650,7 @@ func Test_normal23_K()
   call setline(1, '---')
   call assert_fails('normal! ggv2lK', 'E349:')
   call setline(1, ['abc', 'xyz'])
-  call assert_fails("normal! gg2lv2h\<C-]>", 'E426:')
+  call assert_fails("normal! gg2lv2h\<C-]>", 'E433:')
   call assert_beeps("normal! ggVjK")
 
   " clean up
diff --git a/src/nvim/testdir/test_quickfix.vim b/src/nvim/testdir/test_quickfix.vim
index dcedfe26a2..99d9c9c1fa 100644
--- a/src/nvim/testdir/test_quickfix.vim
+++ b/src/nvim/testdir/test_quickfix.vim
@@ -740,7 +740,7 @@ func s:test_xhelpgrep(cchar)
   " Search for non existing help string
   call assert_fails('Xhelpgrep a1b2c3', 'E480:')
   " Invalid regular expression
-  call assert_fails('Xhelpgrep \@<!', 'E480:')
+  call assert_fails('Xhelpgrep \@<!', 'E866:')
 endfunc
 
 func Test_helpgrep()
@@ -4101,8 +4101,8 @@ endfunc
 
 func Test_lvimgrep_crash2()
   au BufNewFile x sfind
-  call assert_fails('lvimgrep x x', 'E480:')
-  call assert_fails('lvimgrep x x x', 'E480:')
+  call assert_fails('lvimgrep x x', 'E471:')
+  call assert_fails('lvimgrep x x x', 'E471:')
 
   au! BufNewFile
 endfunc
diff --git a/src/nvim/testdir/test_random.vim b/src/nvim/testdir/test_random.vim
index 6d3f7dcfd9..fb1c9ab6cd 100644
--- a/src/nvim/testdir/test_random.vim
+++ b/src/nvim/testdir/test_random.vim
@@ -33,11 +33,11 @@ func Test_Rand()
   endif
   call assert_fails('echo srand([1])', 'E745:')
   call assert_fails('echo rand("burp")', 'E475:')
-  call assert_fails('echo rand([1, 2, 3])', 'E475:')
-  call assert_fails('echo rand([[1], 2, 3, 4])', 'E475:')
-  call assert_fails('echo rand([1, [2], 3, 4])', 'E475:')
-  call assert_fails('echo rand([1, 2, [3], 4])', 'E475:')
-  call assert_fails('echo rand([1, 2, 3, [4]])', 'E475:')
+  call assert_fails('echo rand([1, 2, 3])', 'E730:')
+  call assert_fails('echo rand([[1], 2, 3, 4])', 'E730:')
+  call assert_fails('echo rand([1, [2], 3, 4])', 'E730:')
+  call assert_fails('echo rand([1, 2, [3], 4])', 'E730:')
+  call assert_fails('echo rand([1, 2, 3, [4]])', 'E730:')
 
   " call test_settime(0)
 endfunc
diff --git a/src/nvim/testdir/test_regexp_latin.vim b/src/nvim/testdir/test_regexp_latin.vim
index 2520273e55..2a9a0e9d50 100644
--- a/src/nvim/testdir/test_regexp_latin.vim
+++ b/src/nvim/testdir/test_regexp_latin.vim
@@ -101,7 +101,7 @@ func Test_multi_failure()
   set re=2
   call assert_fails('/a**', 'E871:')
   call assert_fails('/a*\+', 'E871:')
-  call assert_fails('/a\{a}', 'E870:')
+  call assert_fails('/a\{a}', 'E554:')
   set re=0
 endfunc
 
diff --git a/src/nvim/testdir/test_search.vim b/src/nvim/testdir/test_search.vim
index cb35868b47..e77a022d11 100644
--- a/src/nvim/testdir/test_search.vim
+++ b/src/nvim/testdir/test_search.vim
@@ -1647,8 +1647,8 @@ func Test_search_with_no_last_pat()
     call assert_fails(";//p", 'E35:')
     call assert_fails("??p", 'E35:')
     call assert_fails(";??p", 'E35:')
-    call assert_fails('g//p', 'E476:')
-    call assert_fails('v//p', 'E476:')
+    call assert_fails('g//p', ['E35:', 'E476:'])
+    call assert_fails('v//p', ['E35:', 'E476:'])
     call writefile(v:errors, 'Xresult')
     qall!
   [SCRIPT]
@@ -1669,8 +1669,8 @@ func Test_search_tilde_pat()
     call assert_fails('exe "normal /~\<CR>"', 'E33:')
     call assert_fails('exe "normal ?~\<CR>"', 'E33:')
     set regexpengine=2
-    call assert_fails('exe "normal /~\<CR>"', 'E383:')
-    call assert_fails('exe "normal ?~\<CR>"', 'E383:')
+    call assert_fails('exe "normal /~\<CR>"', ['E33:', 'E383:'])
+    call assert_fails('exe "normal ?~\<CR>"', ['E33:', 'E383:'])
     set regexpengine&
     call writefile(v:errors, 'Xresult')
     qall!
diff --git a/src/nvim/testdir/test_signs.vim b/src/nvim/testdir/test_signs.vim
index aa43477c5f..1f1b3097b1 100644
--- a/src/nvim/testdir/test_signs.vim
+++ b/src/nvim/testdir/test_signs.vim
@@ -483,13 +483,13 @@ func Test_sign_funcs()
   call assert_fails('call sign_place(5, "", "sign1", "@", {"lnum" : 10})',
 	      \ 'E158:')
   call assert_fails('call sign_place(5, "", "sign1", [], {"lnum" : 10})',
-	      \ 'E158:')
+	      \ 'E730:')
   call assert_fails('call sign_place(21, "", "sign1", "Xsign",
 	      \ {"lnum" : -1})', 'E474:')
   call assert_fails('call sign_place(22, "", "sign1", "Xsign",
 	      \ {"lnum" : 0})', 'E474:')
   call assert_fails('call sign_place(22, "", "sign1", "Xsign",
-	      \ {"lnum" : []})', 'E474:')
+	      \ {"lnum" : []})', 'E745:')
   call assert_equal(-1, sign_place(1, "*", "sign1", "Xsign", {"lnum" : 10}))
 
   " Tests for sign_getplaced()
@@ -1731,7 +1731,7 @@ func Test_sign_jump_func()
   call assert_fails("call sign_jump(5, 'g5', 'foo')", 'E157:')
   call assert_fails('call sign_jump([], "", "foo")', 'E745:')
   call assert_fails('call sign_jump(2, [], "foo")', 'E730:')
-  call assert_fails('call sign_jump(2, "", {})', 'E158:')
+  call assert_fails('call sign_jump(2, "", {})', 'E731:')
   call assert_fails('call sign_jump(2, "", "baz")', 'E158:')
 
   sign unplace * group=*
diff --git a/src/nvim/testdir/test_spell.vim b/src/nvim/testdir/test_spell.vim
index f7144bbc7e..d8495fdb9b 100644
--- a/src/nvim/testdir/test_spell.vim
+++ b/src/nvim/testdir/test_spell.vim
@@ -495,7 +495,7 @@ func Test_spellsuggest_expr_errors()
     return [[{}, {}]]
   endfunc
   set spellsuggest=expr:MySuggest3()
-  call assert_fails("call spellsuggest('baord')", 'E728:')
+  call assert_fails("call spellsuggest('baord')", 'E731:')
 
   set nospell spellsuggest&
   delfunc MySuggest
diff --git a/src/nvim/testdir/test_substitute.vim b/src/nvim/testdir/test_substitute.vim
index 9b90205c3d..5b476ddd7f 100644
--- a/src/nvim/testdir/test_substitute.vim
+++ b/src/nvim/testdir/test_substitute.vim
@@ -446,7 +446,7 @@ func Test_substitute_errors()
 
   call assert_fails('s/FOO/bar/', 'E486:')
   call assert_fails('s/foo/bar/@', 'E488:')
-  call assert_fails('s/\(/bar/', 'E476:')
+  call assert_fails('s/\(/bar/', 'E54:')
   call assert_fails('s afooabara', 'E146:')
   call assert_fails('s\\a', 'E10:')
 
@@ -841,9 +841,9 @@ endfunc
 func Test_sub_with_no_last_pat()
   let lines =<< trim [SCRIPT]
     call assert_fails('~', 'E33:')
-    call assert_fails('s//abc/g', 'E476:')
-    call assert_fails('s\/bar', 'E476:')
-    call assert_fails('s\&bar&', 'E476:')
+    call assert_fails('s//abc/g', 'E35:')
+    call assert_fails('s\/bar', 'E35:')
+    call assert_fails('s\&bar&', 'E33:')
     call writefile(v:errors, 'Xresult')
     qall!
   [SCRIPT]
diff --git a/src/nvim/testdir/test_syntax.vim b/src/nvim/testdir/test_syntax.vim
index 29ebe141f7..9d108c6ca2 100644
--- a/src/nvim/testdir/test_syntax.vim
+++ b/src/nvim/testdir/test_syntax.vim
@@ -378,7 +378,7 @@ func Test_syntax_invalid_arg()
   call assert_fails('syntax sync x', 'E404:')
   call assert_fails('syntax keyword Abc a[', 'E789:')
   call assert_fails('syntax keyword Abc a[bc]d', 'E890:')
-  call assert_fails('syntax cluster Abc add=A add=', 'E475:')
+  call assert_fails('syntax cluster Abc add=A add=', 'E406:')
 
   " Test for too many \z\( and unmatched \z\(
   " Not able to use assert_fails() here because both E50:/E879: and E475:
diff --git a/src/nvim/testdir/test_tagfunc.vim b/src/nvim/testdir/test_tagfunc.vim
index ffc1d63b90..bdf5afa5b2 100644
--- a/src/nvim/testdir/test_tagfunc.vim
+++ b/src/nvim/testdir/test_tagfunc.vim
@@ -85,7 +85,7 @@ func Test_tagfunc()
     return v:null
   endfunc
   set tags= tfu=NullTagFunc
-  call assert_fails('tag nothing', 'E426')
+  call assert_fails('tag nothing', 'E433')
   delf NullTagFunc
 
   bwipe!
diff --git a/src/nvim/testdir/test_tagjump.vim b/src/nvim/testdir/test_tagjump.vim
index f3ca5e306b..61bf9e6d0d 100644
--- a/src/nvim/testdir/test_tagjump.vim
+++ b/src/nvim/testdir/test_tagjump.vim
@@ -8,7 +8,7 @@ func Test_ptag_with_notagstack()
   CheckFeature quickfix
 
   set notagstack
-  call assert_fails('ptag does_not_exist_tag_name', 'E426')
+  call assert_fails('ptag does_not_exist_tag_name', 'E433')
   set tagstack&vim
 endfunc
 
@@ -346,7 +346,7 @@ func Test_tagjump_etags()
         \ "Xmain.c,64",
         \ ";;;;\x7f1,0",
 	\ ], 'Xtags')
-  call assert_fails('tag foo', 'E426:')
+  call assert_fails('tag foo', 'E431:')
 
   call delete('Xtags')
   call delete('Xtags2')
diff --git a/src/nvim/testdir/test_taglist.vim b/src/nvim/testdir/test_taglist.vim
index 0c47fc9445..658485582c 100644
--- a/src/nvim/testdir/test_taglist.vim
+++ b/src/nvim/testdir/test_taglist.vim
@@ -84,13 +84,11 @@ func Test_taglist_ctags_etags()
 endfunc
 
 func Test_tags_too_long()
-  call assert_fails('tag ' . repeat('x', 1020), 'E426')
+  call assert_fails('tag ' . repeat('x', 1020), ['E433', 'E426'])
   tags
 endfunc
 
 func Test_tagfiles()
-  " Nvim: different default for 'tags'.
-  set tags=./tags,tags
   call assert_equal([], tagfiles())
 
   call writefile(["FFoo\tXfoo\t1"], 'Xtags1')
diff --git a/src/nvim/testdir/test_trycatch.vim b/src/nvim/testdir/test_trycatch.vim
index d71bb5bbb8..3dff8fa2d8 100644
--- a/src/nvim/testdir/test_trycatch.vim
+++ b/src/nvim/testdir/test_trycatch.vim
@@ -2000,13 +2000,11 @@ endfunc
 func Test_try_catch_errors()
   call assert_fails('throw |', 'E471:')
   call assert_fails("throw \n ", 'E471:')
-  call assert_fails('catch abc', 'E603:')
+  call assert_fails('catch abc', 'E654:')
   call assert_fails('try | let i = 1| finally | catch | endtry', 'E604:')
   call assert_fails('finally', 'E606:')
   call assert_fails('try | finally | finally | endtry', 'E607:')
-  " v8.2.3486 has been ported, but v8.2.1183 hasn't, so E170 appears here.
-  " call assert_fails('try | for i in range(5) | endif | endtry', 'E580:')
-  call assert_fails('try | for i in range(5) | endif | endtry', 'E170:')
+  call assert_fails('try | for i in range(5) | endif | endtry', 'E580:')
   call assert_fails('try | while v:true | endtry', 'E170:')
   call assert_fails('try | if v:true | endtry', 'E171:')
 endfunc
diff --git a/src/nvim/testdir/test_utf8.vim b/src/nvim/testdir/test_utf8.vim
index 2fced0dd2f..8e13ed778f 100644
--- a/src/nvim/testdir/test_utf8.vim
+++ b/src/nvim/testdir/test_utf8.vim
@@ -21,7 +21,7 @@ func Test_strchars()
     call assert_equal(exp[i][1], inp[i]->strchars(0))
     call assert_equal(exp[i][2], strchars(inp[i], 1))
   endfor
-  call assert_fails("let v=strchars('abc', [])", 'E474:')
+  call assert_fails("let v=strchars('abc', [])", 'E745:')
   call assert_fails("let v=strchars('abc', 2)", 'E474:')
 endfunc
 
diff --git a/src/nvim/testdir/test_winbuf_close.vim b/src/nvim/testdir/test_winbuf_close.vim
index f4878c2397..643c1068bd 100644
--- a/src/nvim/testdir/test_winbuf_close.vim
+++ b/src/nvim/testdir/test_winbuf_close.vim
@@ -115,7 +115,7 @@ func Test_winbuf_close()
   call assert_equal('Xtest2', bufname('%'))
   quit!
   call assert_equal('Xtest3', bufname('%'))
-  call assert_fails('silent! quit!', 'E162')
+  call assert_fails('silent! quit!', 'E37')
   call assert_equal('Xtest1', bufname('%'))
 
   call delete('Xtest1')
diff --git a/src/nvim/testdir/test_writefile.vim b/src/nvim/testdir/test_writefile.vim
index 5ee13ef144..8fb4c8fa4c 100644
--- a/src/nvim/testdir/test_writefile.vim
+++ b/src/nvim/testdir/test_writefile.vim
@@ -325,7 +325,7 @@ func Test_write_autocmd_unloadbuf_lockmark()
     autocmd BufWritePre Xfile enew | write
   augroup END
   e Xfile
-  call assert_fails('lockmarks write', 'E203:')
+  call assert_fails('lockmarks write', ['E32', 'E203:'])
   augroup WriteTest
     au!
   augroup END
diff --git a/src/nvim/testing.c b/src/nvim/testing.c
index 45134db14f..9dd41224da 100644
--- a/src/nvim/testing.c
+++ b/src/nvim/testing.c
@@ -14,6 +14,12 @@
 # include "testing.c.generated.h"
 #endif
 
+static char e_assert_fails_second_arg[]
+  = N_("E856: assert_fails() second argument must be a string or a list with one or two strings");
+static char e_assert_fails_fourth_argument[]
+  = N_("E1115: assert_fails() fourth argument must be a number");
+static char e_assert_fails_fifth_argument[]
+  = N_("E1116: assert_fails() fifth argument must be a string");
 static char e_calling_test_garbagecollect_now_while_v_testing_is_not_set[]
   = N_("E1142: Calling test_garbagecollect_now() while v:testing is not set");
 
@@ -68,7 +74,7 @@ static void ga_concat_esc(garray_T *gap, const char_u *p, int clen)
     case '\\':
       ga_concat(gap, "\\\\"); break;
     default:
-      if (*p < ' ') {
+      if (*p < ' ' || *p == 0x7f) {
         vim_snprintf((char *)buf, NUMBUFLEN, "\\x%02x", *p);
         ga_concat(gap, (char *)buf);
       } else {
@@ -124,7 +130,10 @@ static void fill_assert_error(garray_T *gap, typval_T *opt_msg_tv, char_u *exp_s
   bool did_copy = false;
   int omitted = 0;
 
-  if (opt_msg_tv->v_type != VAR_UNKNOWN) {
+  if (opt_msg_tv->v_type != VAR_UNKNOWN
+      && !(opt_msg_tv->v_type == VAR_STRING
+           && (opt_msg_tv->vval.v_string == NULL
+               || *opt_msg_tv->vval.v_string == NUL))) {
     tofree = (char_u *)encode_tv2echo(opt_msg_tv, NULL);
     ga_concat(gap, (char *)tofree);
     xfree(tofree);
@@ -244,13 +253,12 @@ static int assert_match_common(typval_T *argvars, assert_type_T atype)
 {
   char buf1[NUMBUFLEN];
   char buf2[NUMBUFLEN];
+  const int called_emsg_before = called_emsg;
   const char *const pat = tv_get_string_buf_chk(&argvars[0], buf1);
   const char *const text = tv_get_string_buf_chk(&argvars[1], buf2);
 
-  if (pat == NULL || text == NULL) {
-    emsg(_(e_invarg));
-  } else if (pattern_match((char *)pat, (char *)text, false)
-             != (atype == ASSERT_MATCH)) {
+  if (called_emsg == called_emsg_before
+      && pattern_match(pat, text, false) != (atype == ASSERT_MATCH)) {
     garray_T ga;
     prepare_assert_error(&ga);
     fill_assert_error(&ga, &argvars[2], NULL, &argvars[0], &argvars[1], atype);
@@ -351,11 +359,12 @@ static int assert_equalfile(typval_T *argvars)
 {
   char buf1[NUMBUFLEN];
   char buf2[NUMBUFLEN];
+  const int called_emsg_before = called_emsg;
   const char *const fname1 = tv_get_string_buf_chk(&argvars[0], buf1);
   const char *const fname2 = tv_get_string_buf_chk(&argvars[1], buf2);
   garray_T ga;
 
-  if (fname1 == NULL || fname2 == NULL) {
+  if (called_emsg > called_emsg_before) {
     return 0;
   }
 
@@ -477,11 +486,13 @@ void f_assert_fails(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   garray_T ga;
   int save_trylevel = trylevel;
   const int called_emsg_before = called_emsg;
+  char *wrong_arg_msg = NULL;
 
   // trylevel must be zero for a ":throw" command to be considered failed
   trylevel = 0;
   suppress_errthrow = true;
   emsg_silent = true;
+  emsg_assert_fails_used = true;
 
   do_cmdline_cmd(cmd);
   if (called_emsg == called_emsg_before) {
@@ -493,13 +504,75 @@ void f_assert_fails(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     rettv->vval.v_number = 1;
   } else if (argvars[1].v_type != VAR_UNKNOWN) {
     char buf[NUMBUFLEN];
-    const char *const error = tv_get_string_buf_chk(&argvars[1], buf);
+    const char *expected;
+    bool error_found = false;
+    int error_found_index = 1;
+    char *actual = emsg_assert_fails_msg == NULL ? "[unknown]" : emsg_assert_fails_msg;
+
+    if (argvars[1].v_type == VAR_STRING) {
+      expected = tv_get_string_buf_chk(&argvars[1], buf);
+      error_found = expected == NULL || strstr(actual, expected) == NULL;
+    } else if (argvars[1].v_type == VAR_LIST) {
+      const list_T *const list = argvars[1].vval.v_list;
+      if (list == NULL || tv_list_len(list) < 1 || tv_list_len(list) > 2) {
+        wrong_arg_msg = e_assert_fails_second_arg;
+        goto theend;
+      }
+      const typval_T *tv = TV_LIST_ITEM_TV(tv_list_first(list));
+      expected = tv_get_string_buf_chk(tv, buf);
+      if (!pattern_match(expected, actual, false)) {
+        error_found = true;
+      } else if (tv_list_len(list) == 2) {
+        tv = TV_LIST_ITEM_TV(tv_list_last(list));
+        actual = get_vim_var_str(VV_ERRMSG);
+        expected = tv_get_string_buf_chk(tv, buf);
+        if (!pattern_match(expected, actual, false)) {
+          error_found = true;
+        }
+      }
+    } else {
+      wrong_arg_msg = e_assert_fails_second_arg;
+      goto theend;
+    }
 
-    if (error == NULL
-        || strstr(get_vim_var_str(VV_ERRMSG), error) == NULL) {
+    if (!error_found && argvars[2].v_type != VAR_UNKNOWN
+        && argvars[3].v_type != VAR_UNKNOWN) {
+      if (argvars[3].v_type != VAR_NUMBER) {
+        wrong_arg_msg = e_assert_fails_fourth_argument;
+        goto theend;
+      } else if (argvars[3].vval.v_number >= 0
+                 && argvars[3].vval.v_number != emsg_assert_fails_lnum) {
+        error_found = true;
+        error_found_index = 3;
+      }
+      if (!error_found && argvars[4].v_type != VAR_UNKNOWN) {
+        if (argvars[4].v_type != VAR_STRING) {
+          wrong_arg_msg = e_assert_fails_fifth_argument;
+          goto theend;
+        } else if (argvars[4].vval.v_string != NULL
+                   && !pattern_match(argvars[4].vval.v_string,
+                                     emsg_assert_fails_context, false)) {
+          error_found = true;
+          error_found_index = 4;
+        }
+      }
+    }
+
+    if (error_found) {
+      typval_T actual_tv;
       prepare_assert_error(&ga);
-      fill_assert_error(&ga, &argvars[2], NULL, &argvars[1],
-                        get_vim_var_tv(VV_ERRMSG), ASSERT_OTHER);
+      if (error_found_index == 3) {
+        actual_tv.v_type = VAR_NUMBER;
+        actual_tv.vval.v_number = emsg_assert_fails_lnum;
+      } else if (error_found_index == 4) {
+        actual_tv.v_type = VAR_STRING;
+        actual_tv.vval.v_string = emsg_assert_fails_context;
+      } else {
+        actual_tv.v_type = VAR_STRING;
+        actual_tv.vval.v_string = actual;
+      }
+      fill_assert_error(&ga, &argvars[2], NULL,
+                        &argvars[error_found_index], &actual_tv, ASSERT_OTHER);
       ga_concat(&ga, ": ");
       assert_append_cmd_or_arg(&ga, argvars, cmd);
       assert_error(&ga);
@@ -508,11 +581,17 @@ void f_assert_fails(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     }
   }
 
+theend:
   trylevel = save_trylevel;
   suppress_errthrow = false;
   emsg_silent = false;
   emsg_on_display = false;
+  emsg_assert_fails_used = false;
+  XFREE_CLEAR(emsg_assert_fails_msg);
   set_vim_var_string(VV_ERRMSG, NULL, 0);
+  if (wrong_arg_msg != NULL) {
+    emsg(_(wrong_arg_msg));
+  }
 }
 
 // "assert_false(actual[, msg])" function