API: return non-generic VimL errors

- Return VimL errors instead of generic errors for:
  - nvim_call_function
  - nvim_call_dict_function
- Fix tests which were silently broken before this change.

This violates #6150 where we agreed not to translate API errors.  But
that can be fixed later.

src/nvim/api/vim.c

@@ -46,8 +46,7 @@
 
 /// Executes an ex-command.
 ///
-/// On parse error: forwards the Vim error; does not update v:errmsg.
-/// On runtime error: forwards the Vim error; does not update v:errmsg.
+/// On execution error: fails with VimL error, does not update v:errmsg.
 ///
 /// @param command  Ex-command string
 /// @param[out] err Error details (Vim error), if any
@@ -103,7 +102,8 @@ Dictionary nvim_get_hl_by_id(Integer hl_id, Boolean rgb, Error *err)
 }
 
 /// Passes input keys to Nvim.
-/// On VimL error: Does not fail, but updates v:errmsg.
+///
+/// On execution error: does not fail, but updates v:errmsg.
 ///
 /// @param keys         to be typed
 /// @param mode         mapping options
@@ -169,7 +169,8 @@ void nvim_feedkeys(String keys, String mode, Boolean escape_csi)
 }
 
 /// Passes keys to Nvim as raw user-input.
-/// On VimL error: Does not fail, but updates v:errmsg.
+///
+/// On execution error: does not fail, but updates v:errmsg.
 ///
 /// Unlike `nvim_feedkeys`, this uses a lower-level input buffer and the call
 /// is not deferred. This is the most reliable way to send real user input.
@@ -213,8 +214,7 @@ String nvim_replace_termcodes(String str, Boolean from_part, Boolean do_lt,
 /// Executes an ex-command and returns its (non-error) output.
 /// Shell |:!| output is not captured.
 ///
-/// On parse error: forwards the Vim error; does not update v:errmsg.
-/// On runtime error: forwards the Vim error; does not update v:errmsg.
+/// On execution error: fails with VimL error, does not update v:errmsg.
 ///
 /// @param command  Ex-command string
 /// @param[out] err Error details (Vim error), if any
@@ -259,7 +259,8 @@ theend:
 
 /// Evaluates a VimL expression (:help expression).
 /// Dictionaries and Lists are recursively expanded.
-/// On VimL error: Returns a generic error; v:errmsg is not updated.
+///
+/// On execution error: fails with generic error; v:errmsg is not updated.
 ///
 /// @param expr     VimL expression string
 /// @param[out] err Error details, if any
@@ -331,18 +332,23 @@ static Object _call_function(String fn, Array args, dict_T *self, Error *err)
   }
 
   try_start();
-  // Call the function
+  msg_first_ignored_err = NULL;
+
   typval_T rettv;
   int dummy;
   int r = call_func((char_u *)fn.data, (int)fn.size, &rettv, (int)args.size,
                     vim_args, NULL, curwin->w_cursor.lnum,
                     curwin->w_cursor.lnum, &dummy, true, NULL, self);
-  if (r == FAIL) {
-    api_set_error(err, kErrorTypeException, "Error calling function");
+  // call_func() retval is deceptive; must also check did_emsg et al.
+  if (msg_first_ignored_err
+      && (r == FAIL || (did_emsg && force_abort && !current_exception))) {
+    api_set_error(err, kErrorTypeException, msg_first_ignored_err);
   }
   if (!try_end(err)) {
     rv = vim_to_object(&rettv);
   }
+  xfree(msg_first_ignored_err);
+  msg_first_ignored_err = NULL;
   tv_clear(&rettv);
 
 free_vim_args:
@@ -355,7 +361,7 @@ free_vim_args:
 
 /// Calls a VimL function with the given arguments.
 ///
-/// On VimL error: Returns a generic error; v:errmsg is not updated.
+/// On execution error: fails with VimL error, does not update v:errmsg.
 ///
 /// @param fn       Function to call
 /// @param args     Function arguments packed in an Array
@@ -369,6 +375,8 @@ Object nvim_call_function(String fn, Array args, Error *err)
 
 /// Calls a VimL |Dictionary-function| with the given arguments.
 ///
+/// On execution error: fails with VimL error, does not update v:errmsg.
+///
 /// @param dict Dictionary, or String evaluating to a VimL |self| dict
 /// @param fn Name of the function defined on the VimL dict
 /// @param args Function arguments packed in an Array

src/nvim/eval.c

@@ -6241,20 +6241,21 @@ bool set_ref_in_func(char_u *name, ufunc_T *fp_in, int copyID)
 /// invoked function uses them. It is called like this:
 ///   new_argcount = argv_func(current_argcount, argv, called_func_argcount)
 ///
-/// Return FAIL when the function can't be called,  OK otherwise.
-/// Also returns OK when an error was encountered while executing the function.
+/// @return FAIL if function cannot be called, else OK (even if an error
+///         occurred while executing the function! Use `msg_first_ignored_err`
+///         to get the error)
 int
 call_func(
     const char_u *funcname,         // name of the function
     int len,                        // length of "name"
-    typval_T *rettv,                // return value goes here
+    typval_T *rettv,                // [out] value goes here
     int argcount_in,                // number of "argvars"
     typval_T *argvars_in,           // vars for arguments, must have "argcount"
                                     // PLUS ONE elements!
     ArgvFunc argv_func,             // function to fill in argvars
     linenr_T firstline,             // first line of range
     linenr_T lastline,              // last line of range
-    int *doesrange,                 // return: function handled range
+    int *doesrange,                 // [out] function handled range
     bool evaluate,
     partial_T *partial,             // optional, can be NULL
     dict_T *selfdict_in             // Dictionary for "self"
@@ -6428,21 +6429,25 @@ call_func(
   return ret;
 }
 
-/*
- * Give an error message with a function name.  Handle <SNR> things.
- * "ermsg" is to be passed without translation, use N_() instead of _().
- */
+/// Give an error message with a function name.  Handle <SNR> things.
+///
+/// @param ermsg must be passed without translation (use N_() instead of _()).
+/// @param name function name
 static void emsg_funcname(char *ermsg, char_u *name)
 {
-  char_u      *p;
+  char_u *p;
 
-  if (*name == K_SPECIAL)
+  if (*name == K_SPECIAL) {
     p = concat_str((char_u *)"<SNR>", name + 3);
-  else
+  } else {
     p = name;
+  }
+
   EMSG2(_(ermsg), p);
-  if (p != name)
+
+  if (p != name) {
     xfree(p);
+  }
 }
 
 /*

src/nvim/message.c

@@ -67,6 +67,7 @@ static char_u   *confirm_msg_tail;              /* tail of confirm_msg */
 
 MessageHistoryEntry *first_msg_hist = NULL;
 MessageHistoryEntry *last_msg_hist = NULL;
+char *msg_first_ignored_err = NULL;
 static int msg_hist_len = 0;
 
 static FILE *verbose_fd = NULL;
@@ -504,6 +505,9 @@ int emsg(const char_u *s_)
     if (cause_errthrow((char_u *)s, severe, &ignore) == true) {
       if (!ignore) {
         did_emsg = true;
+        if (msg_first_ignored_err == NULL) {
+          msg_first_ignored_err = xstrdup(s);
+        }
       }
       return true;
     }

src/nvim/message.h

@@ -85,6 +85,10 @@ extern MessageHistoryEntry *first_msg_hist;
 /// Last message
 extern MessageHistoryEntry *last_msg_hist;
 
+/// Abort-causing non-exception error ignored by emsg(), needed by callers
+/// (RPC API) of call_func() to get error details when messages are disabled.
+extern char *msg_first_ignored_err;
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "message.h.generated.h"
 #endif

test/functional/api/server_requests_spec.lua

@@ -250,7 +250,7 @@ describe('server -> client', function()
     end)
 
     after_each(function()
-      funcs.jobstop(jobid)
+      pcall(funcs.jobstop, jobid)
     end)
 
     if helpers.pending_win32(pending) then return end

test/functional/api/vim_spec.lua

@@ -5,6 +5,7 @@ local global_helpers = require('test.helpers')
 local NIL = helpers.NIL
 local clear, nvim, eq, neq = helpers.clear, helpers.nvim, helpers.eq, helpers.neq
 local command = helpers.command
+local eval = helpers.eval
 local funcs = helpers.funcs
 local iswin = helpers.iswin
 local meth_pcall = helpers.meth_pcall
@@ -40,20 +41,20 @@ describe('api', function()
       os.remove(fname)
     end)
 
-    it("parse error: fails (specific error), does NOT update v:errmsg", function()
-      -- Most API methods return generic errors (or no error) if a VimL
-      -- expression fails; nvim_command returns the VimL error details.
+    it('VimL validation error: fails with specific error', function()
       local status, rv = pcall(nvim, "command", "bogus_command")
       eq(false, status)                       -- nvim_command() failed.
       eq("E492:", string.match(rv, "E%d*:"))  -- VimL error was returned.
-      eq("", nvim("eval", "v:errmsg"))        -- v:errmsg was not updated.
+      eq('', nvim('eval', 'v:errmsg'))        -- v:errmsg was not updated.
+      eq('', eval('v:exception'))
     end)
 
-    it("runtime error: fails (specific error)", function()
+    it('VimL execution error: fails with specific error', function()
       local status, rv = pcall(nvim, "command_output", "buffer 23487")
       eq(false, status)                 -- nvim_command() failed.
       eq("E86: Buffer 23487 does not exist", string.match(rv, "E%d*:.*"))
-      eq("", nvim("eval", "v:errmsg"))  -- v:errmsg was not updated.
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
+      eq('', eval('v:exception'))
     end)
   end)
 
@@ -109,21 +110,21 @@ describe('api', function()
       eq(':!echo foo\r\n\nfoo'..win_lf..'\n', nvim('command_output', [[!echo foo]]))
     end)
 
-    it("parse error: fails (specific error), does NOT update v:errmsg", function()
+    it('VimL validation error: fails with specific error', function()
       local status, rv = pcall(nvim, "command_output", "bogus commannnd")
       eq(false, status)                 -- nvim_command_output() failed.
       eq("E492: Not an editor command: bogus commannnd",
          string.match(rv, "E%d*:.*"))
-      eq("", nvim("eval", "v:errmsg"))  -- v:errmsg was not updated.
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
       -- Verify NO hit-enter prompt.
       eq({mode='n', blocking=false}, nvim("get_mode"))
     end)
 
-    it("runtime error: fails (specific error)", function()
+    it('VimL execution error: fails with specific error', function()
       local status, rv = pcall(nvim, "command_output", "buffer 42")
       eq(false, status)                 -- nvim_command_output() failed.
       eq("E86: Buffer 42 does not exist", string.match(rv, "E%d*:.*"))
-      eq("", nvim("eval", "v:errmsg"))  -- v:errmsg was not updated.
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
       -- Verify NO hit-enter prompt.
       eq({mode='n', blocking=false}, nvim("get_mode"))
     end)
@@ -149,7 +150,7 @@ describe('api', function()
       local status, rv = pcall(nvim, "eval", "bogus expression")
       eq(false, status)                 -- nvim_eval() failed.
       ok(nil ~= string.find(rv, "Failed to evaluate expression"))
-      eq("", nvim("eval", "v:errmsg"))  -- v:errmsg was not updated.
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
     end)
   end)
 
@@ -160,12 +161,39 @@ describe('api', function()
       eq(17, nvim('call_function', 'eval', {17}))
       eq('foo', nvim('call_function', 'simplify', {'this/./is//redundant/../../../foo'}))
     end)
-    it("VimL error: fails (generic error), does NOT update v:errmsg", function()
-      local status, rv = pcall(nvim, "call_function", "bogus function", {"arg1"})
-      eq(false, status)                 -- nvim_call_function() failed.
-      ok(nil ~= string.find(rv, "Error calling function"))
-      eq("", nvim("eval", "v:errmsg"))  -- v:errmsg was not updated.
+
+    it("VimL validation error: returns specific error, does NOT update v:errmsg", function()
+      expect_err('E117: Unknown function: bogus function', request,
+                 'nvim_call_function', 'bogus function', {'arg1'})
+      expect_err('E119: Not enough arguments for function: atan', request,
+                 'nvim_call_function', 'atan', {})
+      eq('', eval('v:exception'))
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
     end)
+
+    it("VimL error: returns error details, does NOT update v:errmsg", function()
+      expect_err('E808: Number or Float required', request,
+                 'nvim_call_function', 'atan', {'foo'})
+      expect_err('Invalid channel stream "xxx"', request,
+                 'nvim_call_function', 'chanclose', {999, 'xxx'})
+      expect_err('E900: Invalid channel id', request,
+                 'nvim_call_function', 'chansend', {999, 'foo'})
+      eq('', eval('v:exception'))
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
+    end)
+
+    it("VimL exception: returns exception details, does NOT update v:errmsg", function()
+      source([[
+        function! Foo() abort
+          throw 'wtf'
+        endfunction
+      ]])
+      expect_err('wtf', request,
+                 'nvim_call_function', 'Foo', {})
+      eq('', eval('v:exception'))
+      eq('', eval('v:errmsg'))  -- v:errmsg was not updated.
+    end)
+
     it('validates args', function()
       local too_many_args = { 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x', 'x' }
       source([[
@@ -216,7 +244,7 @@ describe('api', function()
                  'nvim_call_dict_function', 'g:d', 'baz', {1,2})
       expect_err('Not a function: meep', request,
                  'nvim_call_dict_function', 'g:d', 'meep', {1,2})
-      expect_err('Error calling function', request,
+      expect_err('E117: Unknown function: f', request,
                  'nvim_call_dict_function', { f = '' }, 'f', {1,2})
       expect_err('Not a function: f', request,
                  'nvim_call_dict_function', "{ 'f': '' }", 'f', {1,2})

test/functional/eval/match_functions_spec.lua

@@ -6,6 +6,7 @@ local clear = helpers.clear
 local funcs = helpers.funcs
 local command = helpers.command
 local exc_exec = helpers.exc_exec
+local expect_err = helpers.expect_err
 
 before_each(clear)
 
@@ -40,9 +41,11 @@ describe('setmatches()', function()
   end)
 
   it('fails with -1 if highlight group is not defined', function()
-    eq(-1, funcs.setmatches({{group=1, pattern=2, id=3, priority=4}}))
+    expect_err('E28: No such highlight group name: 1', funcs.setmatches,
+               {{group=1, pattern=2, id=3, priority=4}})
     eq({}, funcs.getmatches())
-    eq(-1, funcs.setmatches({{group=1, pos1={2}, pos2={6}, id=3, priority=4, conceal=5}}))
+    expect_err('E28: No such highlight group name: 1', funcs.setmatches,
+               {{group=1, pos1={2}, pos2={6}, id=3, priority=4, conceal=5}})
     eq({}, funcs.getmatches())
   end)
 end)

test/functional/eval/server_spec.lua

@@ -5,6 +5,7 @@ local clear, funcs, meths = helpers.clear, helpers.funcs, helpers.meths
 local iswin = helpers.iswin
 local ok = helpers.ok
 local matches = helpers.matches
+local expect_err = helpers.expect_err
 
 local function clear_serverlist()
   for _, server in pairs(funcs.serverlist()) do
@@ -89,19 +90,20 @@ describe('server', function()
     s = funcs.serverstart(v4)
     if #s > 0 then
       table.insert(expected, v4)
-      funcs.serverstart(v4)  -- exists already; ignore
+      pcall(funcs.serverstart, v4)  -- exists already; ignore
     end
 
     local v6 = '::1:12345'
     s = funcs.serverstart(v6)
     if #s > 0 then
       table.insert(expected, v6)
-      funcs.serverstart(v6)  -- exists already; ignore
+      pcall(funcs.serverstart, v6)  -- exists already; ignore
     end
     eq(expected, funcs.serverlist())
     clear_serverlist()
 
-    funcs.serverstart('127.0.0.1:65536')  -- invalid port
+    expect_err('Failed to start server: invalid argument',
+               funcs.serverstart, '127.0.0.1:65536')  -- invalid port
     eq({}, funcs.serverlist())
   end)
 

test/functional/legacy/file_perm_spec.lua

@@ -15,7 +15,7 @@ describe('Test getting and setting file permissions', function()
 
   it('file permissions', function()
     eq('', call('getfperm', tempfile))
-    eq(0, call('setfperm', tempfile, 'r------'))
+    eq(0, call('setfperm', tempfile, 'r--------'))
 
     call('writefile', {'one'}, tempfile)
     eq(9, call('len', call('getfperm', tempfile)))

test/functional/lua/luaeval_spec.lua

@@ -51,12 +51,12 @@ describe('luaeval()', function()
   end)
   describe('recursive lua values', function()
     it('are successfully transformed', function()
-      funcs.luaeval('rawset(_G, "d", {})')
-      funcs.luaeval('rawset(d, "d", d)')
+      command('lua rawset(_G, "d", {})')
+      command('lua rawset(d, "d", d)')
       eq('\n{\'d\': {...@0}}', funcs.execute('echo luaeval("d")'))
 
-      funcs.luaeval('rawset(_G, "l", {})')
-      funcs.luaeval('table.insert(l, l)')
+      command('lua rawset(_G, "l", {})')
+      command('lua table.insert(l, l)')
       eq('\n[[...@0]]', funcs.execute('echo luaeval("l")'))
     end)
   end)