[resolvergen] add a configuration flag for enable_rewrite_for_single_…

…file

codegen/config/resolver.go

@@ -11,14 +11,15 @@ import (
 )
 
 type ResolverConfig struct {
-	Filename            string         `yaml:"filename,omitempty"`
-	FilenameTemplate    string         `yaml:"filename_template,omitempty"`
-	Package             string         `yaml:"package,omitempty"`
-	Type                string         `yaml:"type,omitempty"`
-	Layout              ResolverLayout `yaml:"layout,omitempty"`
-	DirName             string         `yaml:"dir"`
-	OmitTemplateComment bool           `yaml:"omit_template_comment,omitempty"`
-	ResolverTemplate    string         `yaml:"resolver_template,omitempty"`
+	Filename                   string         `yaml:"filename,omitempty"`
+	FilenameTemplate           string         `yaml:"filename_template,omitempty"`
+	Package                    string         `yaml:"package,omitempty"`
+	Type                       string         `yaml:"type,omitempty"`
+	Layout                     ResolverLayout `yaml:"layout,omitempty"`
+	DirName                    string         `yaml:"dir"`
+	OmitTemplateComment        bool           `yaml:"omit_template_comment,omitempty"`
+	ResolverTemplate           string         `yaml:"resolver_template,omitempty"`
+	EnableRewriteForSingleFile bool           `yaml:"enable_rewrite_for_single_file,omitempty"`
 }
 
 type ResolverLayout string

plugin/resolvergen/resolver.go

@@ -43,6 +43,9 @@ func (m *Plugin) GenerateCode(data *codegen.Data) error {
 
 	switch data.Config.Resolver.Layout {
 	case config.LayoutSingleFile:
+		if data.Config.Resolver.EnableRewriteForSingleFile {
+			return m.generateSingleFileEnableRewrite(data)
+		}
 		return m.generateSingleFile(data)
 	case config.LayoutFollowSchema:
 		return m.generatePerSchema(data)
@@ -96,6 +99,65 @@ func (m *Plugin) generateSingleFile(data *codegen.Data) error {
 	})
 }
 
+func (m *Plugin) generateSingleFileEnableRewrite(data *codegen.Data) error {
+	file := File{}
+	rewriter, err := rewrite.New(data.Config.Resolver.Dir())
+	if err != nil {
+		return err
+	}
+
+	for _, o := range data.Objects {
+		if o.HasResolvers() {
+			caser := cases.Title(language.English, cases.NoLower)
+			rewriter.MarkStructCopied(templates.LcFirst(o.Name) + templates.UcFirst(data.Config.Resolver.Type))
+			rewriter.GetMethodBody(data.Config.Resolver.Type, caser.String(o.Name))
+
+			file.Objects = append(file.Objects, o)
+		}
+
+		for _, f := range o.Fields {
+			if !f.IsResolver {
+				continue
+			}
+
+			structName := templates.LcFirst(o.Name) + templates.UcFirst(data.Config.Resolver.Type)
+			comment := strings.TrimSpace(strings.TrimLeft(rewriter.GetMethodComment(structName, f.GoFieldName), `\`))
+			implementation := strings.TrimSpace(rewriter.GetMethodBody(structName, f.GoFieldName))
+
+			resolver := Resolver{o, f, rewriter.GetPrevDecl(structName, f.GoFieldName), comment, implementation, nil}
+			file.Resolvers = append(file.Resolvers, &resolver)
+		}
+	}
+
+	if _, err := os.Stat(data.Config.Resolver.Filename); err == nil {
+		file.name = data.Config.Resolver.Filename
+		file.imports = rewriter.ExistingImports(file.name)
+		file.RemainingSource = rewriter.RemainingSource(file.name)
+	}
+
+	resolverBuild := &ResolverBuild{
+		File:                &file,
+		PackageName:         data.Config.Resolver.Package,
+		ResolverType:        data.Config.Resolver.Type,
+		HasRoot:             true,
+		OmitTemplateComment: data.Config.Resolver.OmitTemplateComment,
+	}
+
+	newResolverTemplate := resolverTemplate
+	if data.Config.Resolver.ResolverTemplate != "" {
+		newResolverTemplate = readResolverTemplate(data.Config.Resolver.ResolverTemplate)
+	}
+
+	return templates.Render(templates.Options{
+		PackageName: data.Config.Resolver.Package,
+		FileNotice:  `// THIS CODE WILL BE UPDATED WITH SCHEMA CHANGES. PREVIOUS IMPLEMENTATION FOR SCHEMA CHANGES WILL BE KEPT IN THE COMMENT SECTION. IMPLEMENTATION FOR UNCHANGED SCHEMA WILL BE KEPT.`,
+		Filename:    data.Config.Resolver.Filename,
+		Data:        resolverBuild,
+		Packages:    data.Config.Packages,
+		Template:    newResolverTemplate,
+	})
+}
+
 func (m *Plugin) generatePerSchema(data *codegen.Data) error {
 	rewriter, err := rewrite.New(data.Config.Resolver.Dir())
 	if err != nil {

plugin/resolvergen/resolver.gotpl

@@ -48,5 +48,7 @@
 	//  - When renaming or deleting a resolver the old code will be put in here. You can safely delete
 	//    it when you're done.
 	//  - You have helper methods in this file. Move them out to keep these resolver files clean.
+	/*
 	{{ .RemainingSource }}
+	*/
 {{ end }}

plugin/resolvergen/resolver_test.go

@@ -29,6 +29,28 @@ func TestLayoutSingleFile(t *testing.T) {
 	assertNoErrors(t, "github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile/out")
 }
 
+func TestLayoutSingleFileWithEnableRewrite(t *testing.T) {
+	// Ensure the resolver file exists before running the test
+	resolverFilePath := "testdata/singlefile_enable_rewrite/out/resolver.go"
+	_, err := os.Stat(resolverFilePath)
+	if os.IsNotExist(err) {
+		t.Fatalf("Expected resolver file does not exist: %s", resolverFilePath)
+	}
+	require.NoError(t, err)
+
+	cfg, err := config.LoadConfig("testdata/singlefile_enable_rewrite/gqlgen.yml")
+	require.NoError(t, err)
+	p := Plugin{}
+
+	require.NoError(t, cfg.Init())
+
+	data, err := codegen.BuildData(cfg)
+	require.NoError(t, err)
+
+	require.NoError(t, p.GenerateCode(data))
+	assertNoErrors(t, "github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile_enable_rewrite/out")
+}
+
 func TestLayoutFollowSchema(t *testing.T) {
 	testFollowSchemaPersistence(t, "testdata/followschema")
 

plugin/resolvergen/testdata/singlefile/out/resolver.go

@@ -1,21 +1,22 @@
 package customresolver
 
-// THIS CODE IS A STARTING POINT ONLY. IT WILL NOT BE UPDATED WITH SCHEMA CHANGES.
+// THIS CODE WILL BE UPDATED WITH SCHEMA CHANGES. PREVIOUS IMPLEMENTATION FOR SCHEMA CHANGES WILL BE KEPT IN THE COMMENT SECTION. IMPLEMENTATION FOR UNCHANGED SCHEMA WILL BE KEPT.
 
 import (
 	"context"
+	"fmt"
 )
 
 type CustomResolverType struct{}
 
 // Resolver is the resolver for the resolver field.
 func (r *queryCustomResolverType) Resolver(ctx context.Context) (*Resolver, error) {
-	panic("not implemented")
+	panic(fmt.Errorf("not implemented: Resolver - resolver"))
 }
 
 // Name is the resolver for the name field.
 func (r *resolverCustomResolverType) Name(ctx context.Context, obj *Resolver) (string, error) {
-	panic("not implemented")
+	panic(fmt.Errorf("not implemented: Name - name"))
 }
 
 // Query returns QueryResolver implementation.
@@ -26,3 +27,13 @@ func (r *CustomResolverType) Resolver() ResolverResolver { return &resolverCusto
 
 type queryCustomResolverType struct{ *CustomResolverType }
 type resolverCustomResolverType struct{ *CustomResolverType }
+
+// !!! WARNING !!!
+// The code below was going to be deleted when updating resolvers. It has been copied here so you have
+// one last chance to move it out of harms way if you want. There are two reasons this happens:
+//  - When renaming or deleting a resolver the old code will be put in here. You can safely delete
+//    it when you're done.
+//  - You have helper methods in this file. Move them out to keep these resolver files clean.
+/*
+	type CustomResolverType struct{}
+*/

plugin/resolvergen/testdata/singlefile_enable_rewrite/gqlgen.yml

@@ -0,0 +1,17 @@
+schema:
+  - "testdata/schema.graphql"
+
+exec:
+  filename: testdata/singlefile/out/ignored.go
+model:
+  filename: testdata/singlefile/out/generated.go
+resolver:
+  filename: testdata/singlefile/out/resolver.go
+  type: CustomResolverType
+  enable_rewrite_for_single_file: true
+
+models:
+  Resolver:
+    model: github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile/out.Resolver
+
+omit_gqlgen_version_in_file_notice: true

plugin/resolvergen/testdata/singlefile_enable_rewrite/out/model.go

@@ -0,0 +1,13 @@
+package customresolver
+
+import "context"
+
+type Resolver struct{}
+
+type QueryResolver interface {
+	Resolver(ctx context.Context) (*Resolver, error)
+}
+
+type ResolverResolver interface {
+	Name(ctx context.Context, obj *Resolver) (string, error)
+}

plugin/resolvergen/testdata/singlefile_enable_rewrite/out/resolver.go

@@ -0,0 +1,29 @@
+package customresolver
+
+// THIS CODE WILL BE UPDATED WITH SCHEMA CHANGES. PREVIOUS IMPLEMENTATION FOR SCHEMA CHANGES WILL BE KEPT IN THE COMMENT SECTION. IMPLEMENTATION FOR UNCHANGED SCHEMA WILL BE KEPT.
+
+import (
+	"context"
+	"fmt"
+)
+
+type CustomResolverType struct{}
+
+// Resolver is the resolver for the resolver field.
+func (r *queryCustomResolverType) Resolver(ctx context.Context) (*Resolver, error) {
+	panic(fmt.Errorf("not implemented: Resolver - resolver"))
+}
+
+// Name is the resolver for the name field.
+func (r *resolverCustomResolverType) Name(ctx context.Context, obj *Resolver) (string, error) {
+	panic(fmt.Errorf("not implemented: Name - name"))
+}
+
+// Query returns QueryResolver implementation.
+func (r *CustomResolverType) Query() QueryResolver { return &queryCustomResolverType{r} }
+
+// Resolver returns ResolverResolver implementation.
+func (r *CustomResolverType) Resolver() ResolverResolver { return &resolverCustomResolverType{r} }
+
+type queryCustomResolverType struct{ *CustomResolverType }
+type resolverCustomResolverType struct{ *CustomResolverType }