fix: support method call from structures for string-format (#840)

* fix: support method call from structures for string-format

* fix: added test for MR

rule/string-format.go

@@ -211,10 +211,14 @@ func (lintStringFormatRule) getCallName(call *ast.CallExpr) (callName string, ok
 	if selector, ok := call.Fun.(*ast.SelectorExpr); ok {
 		// Scoped function call
 		scope, ok := selector.X.(*ast.Ident)
-		if !ok {
-			return "", false
+		if ok {
+			return scope.Name + "." + selector.Sel.Name, true
+		}
+		// Scoped function call inside structure
+		recv, ok := selector.X.(*ast.SelectorExpr)
+		if ok {
+			return recv.Sel.Name + "." + selector.Sel.Name, true
 		}
-		return scope.Name + "." + selector.Sel.Name, true
 	}
 
 	return "", false

test/string-format_test.go

@@ -21,7 +21,11 @@ func TestStringFormat(t *testing.T) {
 			[]interface{}{
 				"s.Method3[2]",
 				"!/^[Tt][Hh]/",
-				"must not start with 'th'"}}})
+				"must not start with 'th'"},
+			[]interface{}{
+				"s.Method4", // same as before, but called from a struct
+				"!/^[Ot][Tt]/",
+				"must not start with 'ot'"}}})
 }
 
 func TestStringFormatArgumentParsing(t *testing.T) {

testdata/string-format.go

@@ -18,6 +18,16 @@ func (s stringFormatMethods) Method3(a, b, c string) {
 
 }
 
+type stringFormatMethodsInjected struct{}
+
+func (s stringFormatMethodsInjected) Method4(a, b, c string) {
+
+}
+
+type container struct {
+	s stringFormatMethodsInjected
+}
+
 func stringFormat() {
 	stringFormatMethod1("This string is fine", "")
 	stringFormatMethod1("this string is not capitalized", "") // MATCH /must start with a capital letter/
@@ -27,4 +37,9 @@ func stringFormat() {
 		d: "This string is capitalized, but ends with a period."}) // MATCH /string literal doesn't match user defined regex /[^\.]$//
 	s := stringFormatMethods{}
 	s.Method3("", "", "This string starts with th") // MATCH /must not start with 'th'/
+
+	c := container{
+		s: stringFormatMethods{},
+	}
+	c.s.Method4("Other string starts with ot") // MATCH /must not start with 'ot'/
 }