Config option to preserve single file resolvers instead of always rew…

…riting (#3359)

Signed-off-by: Steve Coffman <steve@khanacademy.org>

TESTING.md

@@ -1,7 +1,7 @@
 How to write tests for gqlgen
 ===
 
-Testing generated code is a little tricky, heres how its currently set up.
+Testing generated code is a little tricky, here's how its currently set up.
 
 ### Testing responses from a server
 

codegen/config/resolver.go

@@ -19,6 +19,7 @@ type ResolverConfig struct {
 	DirName             string         `yaml:"dir"`
 	OmitTemplateComment bool           `yaml:"omit_template_comment,omitempty"`
 	ResolverTemplate    string         `yaml:"resolver_template,omitempty"`
+	PreserveResolver    bool           `yaml:"preserve_resolver,omitempty"`
 }
 
 type ResolverLayout string
@@ -55,6 +56,9 @@ func (r *ResolverConfig) Check() error {
 		} else {
 			r.Filename = abs(r.Filename)
 		}
+		if r.PreserveResolver {
+			return fmt.Errorf("preserve_resolver=true cannot be used with layout=%s", r.Layout)
+		}
 	default:
 		return fmt.Errorf("invalid layout %s. must be %s or %s", r.Layout, LayoutSingleFile, LayoutFollowSchema)
 	}

plugin/resolvergen/resolver.go

@@ -53,6 +53,14 @@ func (m *Plugin) GenerateCode(data *codegen.Data) error {
 
 func (m *Plugin) generateSingleFile(data *codegen.Data) error {
 	file := File{}
+
+	if _, err := os.Stat(data.Config.Resolver.Filename); err == nil &&
+		data.Config.Resolver.PreserveResolver {
+		// file already exists and config says not to update resolver
+		// with layout = single so just return
+		return nil
+	}
+
 	rewriter, err := rewrite.New(data.Config.Resolver.Dir())
 	if err != nil {
 		return err
@@ -104,9 +112,14 @@ func (m *Plugin) generateSingleFile(data *codegen.Data) error {
 		newResolverTemplate = readResolverTemplate(data.Config.Resolver.ResolverTemplate)
 	}
 
+	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.`
+	if data.Config.Resolver.PreserveResolver {
+		fileNotice = `// THIS CODE IS A STARTING POINT ONLY. IT WILL NOT BE UPDATED WITH SCHEMA CHANGES.`
+	}
+
 	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.`,
+		FileNotice:  fileNotice,
 		Filename:    data.Config.Resolver.Filename,
 		Data:        resolverBuild,
 		Packages:    data.Config.Packages,

plugin/resolvergen/resolver_test.go

@@ -29,10 +29,35 @@ 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_preserve/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_preserve/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_preserve/out")
+}
+
 func TestLayoutFollowSchema(t *testing.T) {
 	testFollowSchemaPersistence(t, "testdata/followschema")
 
-	b, err := os.ReadFile("testdata/followschema/out/schema.resolvers.go")
+	resolverFilePath := "testdata/followschema/out/schema.resolvers.go"
+	overWriteFile(t, resolverFilePath+".txt", resolverFilePath)
+
+	b, err := os.ReadFile(resolverFilePath)
 	require.NoError(t, err)
 	source := string(b)
 
@@ -45,7 +70,9 @@ func TestLayoutFollowSchema(t *testing.T) {
 func TestLayoutFollowSchemaWithCustomFilename(t *testing.T) {
 	testFollowSchemaPersistence(t, "testdata/filetemplate")
 
-	b, err := os.ReadFile("testdata/filetemplate/out/schema.custom.go")
+	resolverFilePath := "testdata/filetemplate/out/schema.custom.go"
+	overWriteFile(t, resolverFilePath+".txt", resolverFilePath)
+	b, err := os.ReadFile(resolverFilePath)
 	require.NoError(t, err)
 	source := string(b)
 
@@ -126,6 +153,14 @@ func testFollowSchemaPersistence(t *testing.T, dir string) {
 	assertNoErrors(t, "github.com/99designs/gqlgen/plugin/resolvergen/"+dir+"/out")
 }
 
+func overWriteFile(t *testing.T, sourceFile, destinationFile string) {
+	input, err := os.ReadFile(sourceFile)
+	require.NoError(t, err)
+
+	err = os.WriteFile(destinationFile, input, 0644)
+	require.NoError(t, err)
+}
+
 func assertNoErrors(t *testing.T, pkg string) {
 	pkgs, err := packages.Load(&packages.Config{
 		Mode: packages.NeedName |

plugin/resolvergen/testdata/filetemplate/out/schema.custom.go.txt

@@ -0,0 +1,38 @@
+package customresolver
+
+// This file will be automatically regenerated based on the schema, any resolver implementations
+// will be copied through when generating and any unknown code will be moved to the end.
+// Code generated by github.com/99designs/gqlgen
+
+import (
+	"context"
+
+	customresolver "github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile/out"
+)
+
+// Resolver is the resolver for the resolver field.
+func (r *queryCustomResolverType) Resolver(ctx context.Context) (*customresolver.Resolver, error) {
+	// CustomerResolverType.Resolver implementation
+	return nil, nil
+}
+
+// Name is the resolver for the name field.
+func (r *resolverCustomResolverType) Name(ctx context.Context, obj *customresolver.Resolver) (string, error) {
+	// CustomerResolverType.Name implementation
+	return "", nil
+}
+
+// Query returns customresolver.QueryResolver implementation.
+func (r *CustomResolverType) Query() customresolver.QueryResolver { return &queryCustomResolverType{r} }
+
+// Resolver returns customresolver.ResolverResolver implementation.
+func (r *CustomResolverType) Resolver() customresolver.ResolverResolver {
+	return &resolverCustomResolverType{r}
+}
+
+type queryCustomResolverType struct{ *CustomResolverType }
+type resolverCustomResolverType struct{ *CustomResolverType }
+
+func AUserHelperFunction() {
+	// AUserHelperFunction implementation
+}

plugin/resolvergen/testdata/followschema/out/schema.resolvers.go.txt

@@ -0,0 +1,38 @@
+package customresolver
+
+// This file will be automatically regenerated based on the schema, any resolver implementations
+// will be copied through when generating and any unknown code will be moved to the end.
+// Code generated by github.com/99designs/gqlgen
+
+import (
+	"context"
+
+	customresolver "github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile/out"
+)
+
+// Resolver is the resolver for the resolver field.
+func (r *queryCustomResolverType) Resolver(ctx context.Context) (_ *customresolver.Resolver, err error) {
+	// Named return values are supported.
+	return
+}
+
+// Name is the resolver for the name field.
+func (r *resolverCustomResolverType) Name(ctx context.Context, obj *customresolver.Resolver) (string, error) {
+	// CustomerResolverType.Name implementation
+	return "", nil
+}
+
+// Query returns customresolver.QueryResolver implementation.
+func (r *CustomResolverType) Query() customresolver.QueryResolver { return &queryCustomResolverType{r} }
+
+// Resolver returns customresolver.ResolverResolver implementation.
+func (r *CustomResolverType) Resolver() customresolver.ResolverResolver {
+	return &resolverCustomResolverType{r}
+}
+
+type queryCustomResolverType struct{ *CustomResolverType }
+type resolverCustomResolverType struct{ *CustomResolverType }
+
+func AUserHelperFunction() {
+	// AUserHelperFunction implementation
+}

plugin/resolvergen/testdata/singlefile/gqlgen.yml

@@ -8,6 +8,7 @@ model:
 resolver:
   filename: testdata/singlefile/out/resolver.go
   type: CustomResolverType
+  preserve_resolver: false
 
 models:
   Resolver:

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

@@ -4,19 +4,18 @@ package customresolver
 
 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"))
+	panic("not implemented")
 }
 
 // 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"))
+	panic("not implemented")
 }
 
 // Query returns QueryResolver implementation.

plugin/resolvergen/testdata/singlefile_preserve/gqlgen.yml

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

plugin/resolvergen/testdata/singlefile_preserve/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_preserve/out/resolver.go

@@ -0,0 +1,28 @@
+package customresolver
+
+// THIS CODE IS A STARTING POINT ONLY. IT WILL NOT BE UPDATED WITH SCHEMA CHANGES.
+
+import (
+	"context"
+)
+
+type CustomResolverType struct{}
+
+// Resolver is the resolver for the resolver field.
+func (r *queryCustomResolverType) Resolver(ctx context.Context) (*Resolver, error) {
+	panic("not implemented")
+}
+
+// Name is the resolver for the name field.
+func (r *resolverCustomResolverType) Name(ctx context.Context, obj *Resolver) (string, error) {
+	panic("not implemented")
+}
+
+// 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 }