patch 8.2.2381: Vim9: divide by zero does not abort expression execution

Problem:    Vim9: divide by zero does not abort expression execution.
Solution:   Use a "failed" flag. (issue #7704)

src/eval.c

@@ -57,16 +57,21 @@ static char_u *make_expanded_name(char_u *in_start, char_u *expr_start, char_u *
 
 /*
  * Return "n1" divided by "n2", taking care of dividing by zero.
+ * If "failed" is not NULL set it to TRUE when dividing by zero fails.
  */
 	varnumber_T
-num_divide(varnumber_T n1, varnumber_T n2)
+num_divide(varnumber_T n1, varnumber_T n2, int *failed)
 {
     varnumber_T	result;
 
     if (n2 == 0)
     {
 	if (in_vim9script())
+	{
 	    emsg(_(e_divide_by_zero));
+	    if (failed != NULL)
+		*failed = TRUE;
+	}
 	if (n1 == 0)
 	    result = VARNUM_MIN; // similar to NaN
 	else if (n1 < 0)
@@ -82,12 +87,17 @@ num_divide(varnumber_T n1, varnumber_T n2)
 
 /*
  * Return "n1" modulus "n2", taking care of dividing by zero.
+ * If "failed" is not NULL set it to TRUE when dividing by zero fails.
  */
 	varnumber_T
-num_modulus(varnumber_T n1, varnumber_T n2)
+num_modulus(varnumber_T n1, varnumber_T n2, int *failed)
 {
     if (n2 == 0 && in_vim9script())
+    {
 	emsg(_(e_divide_by_zero));
+	if (failed != NULL)
+	    *failed = TRUE;
+    }
     return (n2 == 0) ? 0 : (n1 % n2);
 }
 
@@ -1516,6 +1526,7 @@ tv_op(typval_T *tv1, typval_T *tv2, char_u *op)
     varnumber_T	n;
     char_u	numbuf[NUMBUFLEN];
     char_u	*s;
+    int		failed = FALSE;
 
     // Can't do anything with a Funcref, Dict, v:true on the right.
     if (tv2->v_type != VAR_FUNC && tv2->v_type != VAR_DICT
@@ -1599,8 +1610,10 @@ tv_op(typval_T *tv1, typval_T *tv2, char_u *op)
 			    case '+': n += tv_get_number(tv2); break;
 			    case '-': n -= tv_get_number(tv2); break;
 			    case '*': n *= tv_get_number(tv2); break;
-			    case '/': n = num_divide(n, tv_get_number(tv2)); break;
-			    case '%': n = num_modulus(n, tv_get_number(tv2)); break;
+			    case '/': n = num_divide(n, tv_get_number(tv2),
+							       &failed); break;
+			    case '%': n = num_modulus(n, tv_get_number(tv2),
+							       &failed); break;
 			}
 			clear_tv(tv1);
 			tv1->v_type = VAR_NUMBER;
@@ -1619,7 +1632,7 @@ tv_op(typval_T *tv1, typval_T *tv2, char_u *op)
 		    tv1->v_type = VAR_STRING;
 		    tv1->vval.v_string = s;
 		}
-		return OK;
+		return failed ? FAIL : OK;
 
 	    case VAR_FLOAT:
 #ifdef FEAT_FLOAT
@@ -3196,12 +3209,16 @@ eval6(
 	    else
 #endif
 	    {
+		int	    failed = FALSE;
+
 		if (op == '*')
 		    n1 = n1 * n2;
 		else if (op == '/')
-		    n1 = num_divide(n1, n2);
+		    n1 = num_divide(n1, n2, &failed);
 		else
-		    n1 = num_modulus(n1, n2);
+		    n1 = num_modulus(n1, n2, &failed);
+		if (failed)
+		    return FAIL;
 
 		rettv->v_type = VAR_NUMBER;
 		rettv->vval.v_number = n1;

src/evalvars.c

@@ -1410,8 +1410,10 @@ ex_let_one(
 			    case '+': n = numval + n; break;
 			    case '-': n = numval - n; break;
 			    case '*': n = numval * n; break;
-			    case '/': n = (long)num_divide(numval, n); break;
-			    case '%': n = (long)num_modulus(numval, n); break;
+			    case '/': n = (long)num_divide(numval, n,
+							       &failed); break;
+			    case '%': n = (long)num_modulus(numval, n,
+							       &failed); break;
 			}
 		    }
 		    else if (opt_type == gov_string

src/proto/eval.pro

@@ -1,6 +1,6 @@
 /* eval.c */
-varnumber_T num_divide(varnumber_T n1, varnumber_T n2);
-varnumber_T num_modulus(varnumber_T n1, varnumber_T n2);
+varnumber_T num_divide(varnumber_T n1, varnumber_T n2, int *failed);
+varnumber_T num_modulus(varnumber_T n1, varnumber_T n2, int *failed);
 void eval_init(void);
 void eval_clear(void);
 void fill_evalarg_from_eap(evalarg_T *evalarg, exarg_T *eap, int skip);

src/testdir/test_vim9_assign.vim

@@ -1489,6 +1489,30 @@ def Test_unlet()
   assert_equal('', $ENVVAR)
 enddef
 
+def Test_expr_error_no_assign()
+  var lines =<< trim END
+      vim9script
+      var x = invalid
+      echo x
+  END
+  CheckScriptFailureList(lines, ['E121:', 'E121:'])
+
+  lines =<< trim END
+      vim9script
+      var x = 1 / 0
+      echo x
+  END
+  CheckScriptFailureList(lines, ['E1154:', 'E121:'])
+
+  lines =<< trim END
+      vim9script
+      var x = 1 % 0
+      echo x
+  END
+  CheckScriptFailureList(lines, ['E1154:', 'E121:'])
+enddef
+
+
 def Test_assign_command_modifier()
   var lines =<< trim END
       var verbose = 0

src/testdir/vim9.vim

@@ -69,6 +69,19 @@ def CheckScriptFailure(lines: list<string>, error: string, lnum = -3)
   endtry
 enddef
 
+def CheckScriptFailureList(lines: list<string>, errors: list<string>, lnum = -3)
+  var cwd = getcwd()
+  var fname = 'XScriptFailure' .. s:sequence
+  s:sequence += 1
+  writefile(lines, fname)
+  try
+    assert_fails('so ' .. fname, errors, lines, lnum)
+  finally
+    chdir(cwd)
+    delete(fname)
+  endtry
+enddef
+
 def CheckScriptSuccess(lines: list<string>)
   var cwd = getcwd()
   var fname = 'XScriptSuccess' .. s:sequence

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2381,
 /**/
     2380,
 /**/

src/vim9compile.c

@@ -4294,6 +4294,7 @@ compile_expr6(char_u **arg, cctx_T *cctx, ppconst_T *ppconst)
 	    typval_T	    *tv1 = &ppconst->pp_tv[ppconst_used];
 	    typval_T	    *tv2 = &ppconst->pp_tv[ppconst_used + 1];
 	    varnumber_T	    res = 0;
+	    int		    failed = FALSE;
 
 	    // both are numbers: compute the result
 	    switch (*op)
@@ -4301,12 +4302,14 @@ compile_expr6(char_u **arg, cctx_T *cctx, ppconst_T *ppconst)
 		case '*': res = tv1->vval.v_number * tv2->vval.v_number;
 			  break;
 		case '/': res = num_divide(tv1->vval.v_number,
-							   tv2->vval.v_number);
+						  tv2->vval.v_number, &failed);
 			  break;
 		case '%': res = num_modulus(tv1->vval.v_number,
-							   tv2->vval.v_number);
+						  tv2->vval.v_number, &failed);
 			  break;
 	    }
+	    if (failed)
+		return FAIL;
 	    tv1->vval.v_number = res;
 	    --ppconst->pp_used;
 	}