feat(fixer.go): enhance lookup function to support methods in additio…

…n to functions

feat(fixer_test.go): add unit tests for the enhanced lookup functionality
feat(testdata/stringer.go): add comments and new methods to support testing of new lookup functionality
refactor(fixer.go): use strings package for splitting function names, improving code readability and functionality

fixer.go

@@ -9,6 +9,7 @@ import (
 	"go/parser"
 	"go/token"
 	"os"
+	"strings"
 )
 
 func fix(filename, functionName string) error {
@@ -29,14 +30,40 @@ func lookup(filename, functionName string) (int, int, error) {
 	if err != nil {
 		return 0, 0, err
 	}
+	funcParts := strings.Split(functionName, ".")
 
 	var start, end int
 	ast.Inspect(node, func(n ast.Node) bool {
-		funcDecl, ok := n.(*ast.FuncDecl)
-		if ok && funcDecl.Name.Name == functionName {
-			start = fset.Position(funcDecl.Pos()).Line
-			end = fset.Position(funcDecl.End()).Line
-			return false
+		switch t := n.(type) {
+		case *ast.FuncDecl:
+			if len(funcParts) == 2 {
+				// handle method
+				if t.Name.Name == funcParts[1] {
+					if t.Recv != nil {
+						for _, field := range t.Recv.List {
+							var ident *ast.Ident
+							switch field.Type.(type) {
+							case *ast.Ident:
+								ident = field.Type.(*ast.Ident)
+							case *ast.StarExpr:
+								ident = field.Type.(*ast.StarExpr).X.(*ast.Ident)
+							}
+							if ident != nil && ident.Name == funcParts[0] {
+								start = fset.Position(t.Pos()).Line
+								end = fset.Position(t.End()).Line
+								return false
+							}
+						}
+					}
+				}
+			} else {
+				// handle function
+				if t.Name.Name == functionName {
+					start = fset.Position(t.Pos()).Line
+					end = fset.Position(t.End()).Line
+					return false
+				}
+			}
 		}
 		return true
 	})

fixer_test.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestLookup(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		filename, functionName string
+		start, end             int
+		err                    error
+	}{
+		{"testdata/reachable.go", "Reachable", 5, 7, nil},
+		{"testdata/stringer.go", "myString.String", 12, 14, nil},
+		{"testdata/stringer.go", "myString.Unreachable", 20, 22, nil},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.filename+":"+tt.functionName, func(t *testing.T) {
+			t.Parallel()
+			start, end, err := lookup(tt.filename, tt.functionName)
+			if start != tt.start || end != tt.end || err != tt.err {
+				t.Errorf("lookup(%q, %q) = (%d, %d, %v); want (%d, %d, %v)",
+					tt.filename, tt.functionName, start, end, err, tt.start, tt.end, tt.err)
+			}
+		})
+	}
+}

testdata/stringer.go

@@ -8,10 +8,15 @@ type myString struct {
 	Value string
 }
 
+// NOTE: This function is unreachable but it is neccessary to implement the fmt.Stringer interface
 func (s myString) String() string {
 	return s.Value
 }
 
 func (s myString) Reachable() {
 	return
 }
+
+func (s *myString) Unreachable() {
+	return
+}