appending factories into existing files

internal/di/factories_generator.go

@@ -1,6 +1,8 @@
 package di
 
 import (
+	"bytes"
+	"fmt"
 	"os"
 	"strings"
 
@@ -32,39 +34,80 @@ func (g *FactoriesGenerator) Generate() ([]*File, error) {
 	files := make([]*File, 0, len(servicesByFiles))
 
 	for filename, services := range servicesByFiles {
-		if g.isFactoryFileExist(filename) {
-			continue
-		}
+		var file *File
+		var err error
 
-		file := NewFileBuilder(filename, "factories", FactoriesPackage)
-		file.AddImportAliases(g.container.Imports)
-
-		for _, service := range services {
-			file.Add(
-				jen.Line(),
-				jen.Func().Id("Create"+strings.Title(service.Prefix)+service.Title()).
-					Params(
-						jen.Id("ctx").Qual("context", "Context"),
-						jen.Id("c").Qual(g.params.packageName(LookupPackage), "Container"),
-					).
-					Params(
-						jen.Do(g.container.Type(service.Type)),
-						jen.Error(),
-					).
-					Block(jen.Panic(jen.Lit("not implemented"))),
-			)
+		if g.isFactoryFileExist(filename) {
+			file, err = g.generateAppendFile(filename, services)
+		} else {
+			file, err = g.generateNewFile(filename, services)
 		}
-
-		content, err := file.GetFile()
 		if err != nil {
 			return nil, err
 		}
-		files = append(files, content)
+
+		files = append(files, file)
 	}
 
 	return files, nil
 }
 
+func (g *FactoriesGenerator) generateNewFile(filename string, services []*ServiceDefinition) (*File, error) {
+	file := NewFileBuilder(filename, "factories", FactoriesPackage)
+	file.AddImportAliases(g.container.Imports)
+
+	for _, service := range services {
+		file.Add(
+			jen.Line(),
+			jen.Func().Id("Create"+strings.Title(service.Prefix)+service.Title()).
+				Params(
+					jen.Id("ctx").Qual("context", "Context"),
+					jen.Id("c").Qual(g.params.packageName(LookupPackage), "Container"),
+				).
+				Params(
+					jen.Do(g.container.Type(service.Type)),
+					jen.Error(),
+				).
+				Block(jen.Panic(jen.Lit("not implemented"))),
+		)
+	}
+
+	return file.GetFile()
+}
+
+func (g *FactoriesGenerator) generateAppendFile(filename string, services []*ServiceDefinition) (*File, error) {
+	var content bytes.Buffer
+
+	for _, service := range services {
+		factoryName := strings.Title(service.Prefix) + service.Title()
+		if _, exists := g.container.Factories[factoryName]; exists {
+			continue
+		}
+
+		content.WriteString("\n")
+		content.WriteString(fmt.Sprintf("%#v",
+			jen.Func().Id("Create"+factoryName).
+				Params(
+					jen.Id("ctx").Qual("context", "Context"),
+					jen.Id("c").Qual(g.params.packageName(LookupPackage), "Container"),
+				).
+				Params(
+					jen.Do(g.container.Type(service.Type)),
+					jen.Error(),
+				).
+				Block(jen.Panic(jen.Lit("not implemented"))),
+		))
+		content.WriteString("\n")
+	}
+
+	return &File{
+		Package: FactoriesPackage,
+		Name:    filename,
+		Content: content.Bytes(),
+		Append:  true,
+	}, nil
+}
+
 func (g *FactoriesGenerator) isFactoryFileExist(filename string) bool {
 	_, err := os.Stat(g.workDir + "/" + packageDirs[FactoriesPackage] + "/" + filename)
 

internal/di/file.go

@@ -32,6 +32,7 @@ type File struct {
 	Package PackageType
 	Name    string
 	Content []byte
+	Append  bool
 }
 
 func (f *File) Path() string {
@@ -43,6 +44,10 @@ func (f *File) Path() string {
 	return path + f.Name
 }
 
+func (f *File) IsEmpty() bool {
+	return len(f.Content) == 0
+}
+
 type FileBuilder struct {
 	file        *jen.File
 	fileName    string

internal/di/generator.go

@@ -146,20 +146,28 @@ func (g *Generator) generateFactoriesFiles(container *RootContainerDefinition) e
 		RootPackage:   g.RootPackage(),
 		ErrorHandling: g.ErrorWrapping.Defaults(),
 	}
-	manager := NewFactoriesGenerator(container, g.BaseDir, params)
-	files, err := manager.Generate()
+	generator := NewFactoriesGenerator(container, g.BaseDir, params)
+	files, err := generator.Generate()
 	if err != nil {
 		return err
 	}
 
 	for _, file := range files {
+		if file.IsEmpty() {
+			continue
+		}
 		writer := NewWriter(g.BaseDir)
+		writer.Append = file.Append
 		err = writer.WriteFile(file)
 		if err != nil {
 			return err
 		}
 
-		g.Logger.Info("factories file", file.Path(), "generated")
+		action := "generated"
+		if writer.Append {
+			action = "updated"
+		}
+		g.Logger.Info("factories file", file.Path(), action)
 	}
 
 	return nil
@@ -183,7 +191,7 @@ func (g *Generator) generateUtils() error {
 		return err
 	}
 
-	g.Logger.Info("bitset file", file.Path(), "generated")
+	g.Logger.Info("file", file.Path(), "generated")
 
 	return nil
 }

internal/di/writer.go

@@ -10,6 +10,7 @@ import (
 type Writer struct {
 	WorkDir   string
 	Overwrite bool
+	Append    bool
 	Heading   []byte
 }
 
@@ -24,10 +25,19 @@ func (w *Writer) WriteFile(file *File) error {
 	}
 	filename += file.Name
 
-	if !w.Overwrite && isFileExist(filename) {
-		return errors.Errorf("cannot write to file %s: %w", filename, ErrFileAlreadyExists)
+	if isFileExist(filename) {
+		if w.Append {
+			return w.append(file, filename)
+		}
+		if !w.Overwrite {
+			return errors.Errorf("cannot write to file %s: %w", filename, ErrFileAlreadyExists)
+		}
 	}
 
+	return w.write(file, filename)
+}
+
+func (w *Writer) write(file *File, filename string) error {
 	dir := filepath.Dir(filename)
 	err := os.MkdirAll(dir, 0775)
 	if err != nil {
@@ -42,8 +52,24 @@ func (w *Writer) WriteFile(file *File) error {
 	return nil
 }
 
+func (w *Writer) append(file *File, filename string) error {
+	return appendFile(filename, file.Content, 0644)
+}
+
 func isFileExist(filename string) bool {
 	_, err := os.Stat(filename)
 
 	return err == nil
 }
+
+func appendFile(name string, data []byte, perm os.FileMode) error {
+	f, err := os.OpenFile(name, os.O_APPEND|os.O_WRONLY|os.O_CREATE, perm)
+	if err != nil {
+		return err
+	}
+	_, err = f.Write(data)
+	if err1 := f.Close(); err1 != nil && err == nil {
+		err = err1
+	}
+	return err
+}