Allow custom resolver filenames using filename_template option

This is a squash commit of #1085, required to fix the broken tests and
resolve merge conflicts.

codegen/config/resolver.go

@@ -10,11 +10,12 @@ import (
 )
 
 type ResolverConfig struct {
-	Filename string         `yaml:"filename,omitempty"`
-	Package  string         `yaml:"package,omitempty"`
-	Type     string         `yaml:"type,omitempty"`
-	Layout   ResolverLayout `yaml:"layout,omitempty"`
-	DirName  string         `yaml:"dir"`
+	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"`
 }
 
 type ResolverLayout string

docs/content/config.md

@@ -35,6 +35,7 @@ resolver:
   layout: follow-schema
   dir: graph
   package: graph
+  filename_template: "{name}.resolvers.go"
 
 # Optional: turn on use ` + "`" + `gqlgen:"fieldName"` + "`" + ` tags in your models
 # struct_tag: json

plugin/resolvergen/resolver.go

@@ -88,7 +88,7 @@ func (m *Plugin) generatePerSchema(data *codegen.Data) error {
 
 	for _, o := range data.Objects {
 		if o.HasResolvers() {
-			fn := gqlToResolverName(data.Config.Resolver.Dir(), o.Position.Src.Name)
+			fn := gqlToResolverName(data.Config.Resolver.Dir(), o.Position.Src.Name, data.Config.Resolver.FilenameTemplate)
 			if files[fn] == nil {
 				files[fn] = &File{}
 			}
@@ -109,7 +109,7 @@ func (m *Plugin) generatePerSchema(data *codegen.Data) error {
 			}
 
 			resolver := Resolver{o, f, implementation}
-			fn := gqlToResolverName(data.Config.Resolver.Dir(), f.Position.Src.Name)
+			fn := gqlToResolverName(data.Config.Resolver.Dir(), f.Position.Src.Name, data.Config.Resolver.FilenameTemplate)
 			if files[fn] == nil {
 				files[fn] = &File{}
 			}
@@ -196,9 +196,12 @@ type Resolver struct {
 	Implementation string
 }
 
-func gqlToResolverName(base string, gqlname string) string {
+func gqlToResolverName(base string, gqlname, filenameTmpl string) string {
 	gqlname = filepath.Base(gqlname)
 	ext := filepath.Ext(gqlname)
-
-	return filepath.Join(base, strings.TrimSuffix(gqlname, ext)+".resolvers.go")
+	if filenameTmpl == "" {
+		filenameTmpl = "{name}.resolvers.go"
+	}
+	filename := strings.ReplaceAll(filenameTmpl, "{name}", strings.TrimSuffix(gqlname, ext))
+	return filepath.Join(base, filename)
 }

plugin/resolvergen/resolver_test.go

@@ -31,9 +31,33 @@ func TestLayoutSingleFile(t *testing.T) {
 }
 
 func TestLayoutFollowSchema(t *testing.T) {
-	_ = syscall.Unlink("testdata/followschema/out/resolver.go")
+	testFollowSchemaPersistence(t, "testdata/followschema")
 
-	cfg, err := config.LoadConfig("testdata/followschema/gqlgen.yml")
+	b, err := ioutil.ReadFile("testdata/followschema/out/schema.resolvers.go")
+	require.NoError(t, err)
+	source := string(b)
+
+	require.Contains(t, source, "// CustomerResolverType.Resolver implementation")
+	require.Contains(t, source, "// CustomerResolverType.Name implementation")
+	require.Contains(t, source, "// AUserHelperFunction implementation")
+}
+
+func TestLayoutFollowSchemaWithCustomFilename(t *testing.T) {
+	testFollowSchemaPersistence(t, "testdata/filetemplate")
+
+	b, err := ioutil.ReadFile("testdata/filetemplate/out/schema.custom.go")
+	require.NoError(t, err)
+	source := string(b)
+
+	require.Contains(t, source, "// CustomerResolverType.Resolver implementation")
+	require.Contains(t, source, "// CustomerResolverType.Name implementation")
+	require.Contains(t, source, "// AUserHelperFunction implementation")
+}
+
+func testFollowSchemaPersistence(t *testing.T, dir string) {
+	_ = syscall.Unlink(dir + "/out/resolver.go")
+
+	cfg, err := config.LoadConfig(dir + "/gqlgen.yml")
 	require.NoError(t, err)
 	p := Plugin{}
 
@@ -45,15 +69,7 @@ func TestLayoutFollowSchema(t *testing.T) {
 	}
 
 	require.NoError(t, p.GenerateCode(data))
-	assertNoErrors(t, "github.com/99designs/gqlgen/plugin/resolvergen/testdata/followschema/out")
-
-	b, err := ioutil.ReadFile("testdata/followschema/out/schema.resolvers.go")
-	require.NoError(t, err)
-	source := string(b)
-
-	require.Contains(t, source, "// CustomerResolverType.Resolver implementation")
-	require.Contains(t, source, "// CustomerResolverType.Name implementation")
-	require.Contains(t, source, "// AUserHelperFunction implementation")
+	assertNoErrors(t, "github.com/99designs/gqlgen/plugin/resolvergen/"+dir+"/out")
 }
 
 func assertNoErrors(t *testing.T, pkg string) {

plugin/resolvergen/testdata/filetemplate/gqlgen.yml

@@ -0,0 +1,16 @@
+schema:
+  - "testdata/schema.graphql"
+
+exec:
+  filename: testdata/singlefile/out/ignored.go
+model:
+  filename: testdata/singlefile/out/generated.go
+resolver:
+  type: CustomResolverType
+  layout: follow-schema
+  dir: testdata/filetemplate/out
+  filename_template: "{name}.custom.go"
+
+models:
+  Resolver:
+    model: github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile/out.Resolver

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

@@ -0,0 +1,14 @@
+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/filetemplate/out/resolver.go

@@ -0,0 +1,7 @@
+package customresolver
+
+// This file will not be regenerated automatically.
+//
+// It serves as dependency injection for your app, add any dependencies you require here.
+
+type CustomResolverType struct{}

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

@@ -0,0 +1,41 @@
+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.
+
+import (
+	"context"
+
+	customresolver "github.com/99designs/gqlgen/plugin/resolvergen/testdata/singlefile/out"
+)
+
+func (r *queryCustomResolverType) Resolver(ctx context.Context) (*customresolver.Resolver, error) {
+	// CustomerResolverType.Resolver implementation
+	return nil, nil
+}
+
+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 }
+
+// !!! 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.
+func AUserHelperFunction() {
+	// AUserHelperFunction implementation
+}