chore(function): substr with optional argument

Make the substr function accept the third argument as optional. If the third argument is not given, the string is sliced from the start index to its length.

Author: rabbitstack

pkg/filter/ql/functions/substr.go

@@ -22,7 +22,7 @@ package functions
 type Substr struct{}
 
 func (f Substr) Call(args []interface{}) (interface{}, bool) {
-	if len(args) < 3 {
+	if len(args) < 2 {
 		return false, false
 	}
 
@@ -40,17 +40,23 @@ func (f Substr) Call(args []interface{}) (interface{}, bool) {
 		return false, false
 	}
 
-	switch v := args[2].(type) {
-	case int:
-		end = v
-	case int64:
-		end = int(v)
-	default:
-		return false, false
-	}
+	if len(args) > 2 {
+		switch v := args[2].(type) {
+		case int:
+			end = v
+		case int64:
+			end = int(v)
+		default:
+			return false, false
+		}
 
-	if start >= 0 && (end >= start && end < len(s)) {
-		return s[start:end], true
+		if start >= 0 && (end >= start && end < len(s)) {
+			return s[start:end], true
+		}
+	} else {
+		if start >= 0 && start < len(s) {
+			return s[start:], true
+		}
 	}
 
 	return s, true
@@ -62,7 +68,7 @@ func (f Substr) Desc() FunctionDesc {
 		Args: []FunctionArgDesc{
 			{Keyword: "string", Types: []ArgType{Func, Field, BoundField, BoundSegment, BareBoundVariable}, Required: true},
 			{Keyword: "start", Types: []ArgType{Func, Number}, Required: true},
-			{Keyword: "end", Types: []ArgType{Func, Number}, Required: true},
+			{Keyword: "end", Types: []ArgType{Func, Number}},
 		},
 	}
 	return desc

pkg/filter/ql/functions/substr_test.go

@@ -50,6 +50,14 @@ func TestSubstr(t *testing.T) {
 			[]interface{}{"Hello World!", 6, 7},
 			"W",
 		},
+		{
+			[]interface{}{"Hello World!", 6},
+			"World!",
+		},
+		{
+			[]interface{}{"Hello World!", 20},
+			"Hello World!",
+		},
 	}
 
 	for i, tt := range tests {