Reimplement goTag using FieldMutateHook (#1682)

* Reimplement goTag using a FieldMutateHook

This change does not change the logic of goTag, merely reimplements it using a FieldMutateHook and sets it as the default FieldMutateHook for the modelgen plugin.

* Add repeated tag test

codegen/config/config.go

@@ -239,10 +239,6 @@ func (c *Config) injectTypesFromSchema() error {
 		SkipRuntime: true,
 	}
 
-	c.Directives["goTag"] = DirectiveConfig{
-		SkipRuntime: true,
-	}
-
 	for _, schemaType := range c.Schema.Types {
 		if schemaType == c.Schema.Query || schemaType == c.Schema.Mutation || schemaType == c.Schema.Subscription {
 			continue
@@ -265,15 +261,9 @@ func (c *Config) injectTypesFromSchema() error {
 
 		if schemaType.Kind == ast.Object || schemaType.Kind == ast.InputObject {
 			for _, field := range schemaType.Fields {
-				typeMapField := TypeMapField{
-					ExtraTags: c.Models[schemaType.Name].Fields[field.Name].ExtraTags,
-					FieldName: c.Models[schemaType.Name].Fields[field.Name].FieldName,
-					Resolver:  c.Models[schemaType.Name].Fields[field.Name].Resolver,
-				}
-				directive := false
 				if fd := field.Directives.ForName("goField"); fd != nil {
-					forceResolver := typeMapField.Resolver
-					fieldName := typeMapField.FieldName
+					forceResolver := c.Models[schemaType.Name].Fields[field.Name].Resolver
+					fieldName := c.Models[schemaType.Name].Fields[field.Name].FieldName
 
 					if ra := fd.Arguments.ForName("forceResolver"); ra != nil {
 						if fr, err := ra.Value.Value(nil); err == nil {
@@ -287,38 +277,17 @@ func (c *Config) injectTypesFromSchema() error {
 						}
 					}
 
-					typeMapField.FieldName = fieldName
-					typeMapField.Resolver = forceResolver
-					directive = true
-				}
-
-				for _, goTag := range field.Directives.ForNames("goTag") {
-					key := ""
-					value := field.Name
-					if arg := goTag.Arguments.ForName("key"); arg != nil {
-						if k, err := arg.Value.Value(nil); err == nil {
-							key = k.(string)
-						}
-					}
-
-					if arg := goTag.Arguments.ForName("value"); arg != nil {
-						if v, err := arg.Value.Value(nil); err == nil {
-							value = v.(string)
-						}
-					}
-
-					typeMapField.ExtraTags = append(typeMapField.ExtraTags, key+":\""+value+"\"")
-					directive = true
-				}
-
-				if directive {
 					if c.Models[schemaType.Name].Fields == nil {
 						c.Models[schemaType.Name] = TypeMapEntry{
 							Model:  c.Models[schemaType.Name].Model,
 							Fields: map[string]TypeMapField{},
 						}
 					}
-					c.Models[schemaType.Name].Fields[field.Name] = typeMapField
+
+					c.Models[schemaType.Name].Fields[field.Name] = TypeMapField{
+						FieldName: fieldName,
+						Resolver:  forceResolver,
+					}
 				}
 			}
 		}
@@ -333,10 +302,9 @@ type TypeMapEntry struct {
 }
 
 type TypeMapField struct {
-	Resolver        bool     `yaml:"resolver"`
-	FieldName       string   `yaml:"fieldName"`
-	ExtraTags       []string `yaml:"extraTags"`
-	GeneratedMethod string   `yaml:"-"`
+	Resolver        bool   `yaml:"resolver"`
+	FieldName       string `yaml:"fieldName"`
+	GeneratedMethod string `yaml:"-"`
 }
 
 type StringList []string

docs/content/recipes/modelgen-hook.md

@@ -154,9 +154,11 @@ type ObjectInput struct {
 }
 ```
 
-If a constraint being used during generation shoud not be published during introspection, the directive should be listed with `skip_runtime:true` in gqlgen.yml
+If a constraint being used during generation should not be published during introspection, the directive should be listed with `skip_runtime:true` in gqlgen.yml
 ```yaml
 directives:
   constraint:
     skip_runtime: true
 ```
+
+The built-in directive `@goTag` is implemented using the FieldMutateHook. See: `plugin/modelgen/models.go` function `GoTagFieldHook`

plugin/modelgen/models.go

@@ -16,10 +16,10 @@ type BuildMutateHook = func(b *ModelBuild) *ModelBuild
 
 type FieldMutateHook = func(td *ast.Definition, fd *ast.FieldDefinition, f *Field) (*Field, error)
 
+// defaultFieldMutateHook is the default hook for the Plugin which applies the GoTagFieldHook.
 func defaultFieldMutateHook(td *ast.Definition, fd *ast.FieldDefinition, f *Field) (*Field, error) {
-	return f, nil
+	return GoTagFieldHook(td, fd, f)
 }
-
 func defaultBuildMutateHook(b *ModelBuild) *ModelBuild {
 	return b
 }
@@ -171,14 +171,11 @@ func (m *Plugin) MutateConfig(cfg *config.Config) error {
 					typ = types.NewPointer(typ)
 				}
 
-				tags := []string{`json:"` + field.Name + `"`}
-				tags = append(tags, cfg.Models[schemaType.Name].Fields[field.Name].ExtraTags...)
-
 				f := &Field{
 					Name:        name,
 					Type:        typ,
 					Description: field.Description,
-					Tag:         strings.Join(tags, " "),
+					Tag:         `json:"` + field.Name + `"`,
 				}
 
 				if m.FieldHook != nil {
@@ -254,6 +251,36 @@ func (m *Plugin) MutateConfig(cfg *config.Config) error {
 	return nil
 }
 
+// GoTagFieldHook applies the goTag directive to the generated Field f. When applying the Tag to the field, the field
+// name is used when no value argument is present.
+func GoTagFieldHook(td *ast.Definition, fd *ast.FieldDefinition, f *Field) (*Field, error) {
+	args := make([]string, 0)
+	for _, goTag := range fd.Directives.ForNames("goTag") {
+		key := ""
+		value := fd.Name
+
+		if arg := goTag.Arguments.ForName("key"); arg != nil {
+			if k, err := arg.Value.Value(nil); err == nil {
+				key = k.(string)
+			}
+		}
+
+		if arg := goTag.Arguments.ForName("value"); arg != nil {
+			if v, err := arg.Value.Value(nil); err == nil {
+				value = v.(string)
+			}
+		}
+
+		args = append(args, key+":\""+value+"\"")
+	}
+
+	if len(args) > 0 {
+		f.Tag = f.Tag + " " + strings.Join(args, " ")
+	}
+
+	return f, nil
+}
+
 func isStruct(t types.Type) bool {
 	_, is := t.Underlying().(*types.Struct)
 	return is

plugin/modelgen/models_test.go

@@ -7,8 +7,6 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/vektah/gqlparser/v2/ast"
-
 	"github.com/99designs/gqlgen/codegen/config"
 	"github.com/99designs/gqlgen/plugin/modelgen/out"
 	"github.com/stretchr/testify/require"
@@ -20,7 +18,7 @@ func TestModelGeneration(t *testing.T) {
 	require.NoError(t, cfg.Init())
 	p := Plugin{
 		MutateHook: mutateHook,
-		FieldHook:  mutateFieldHook,
+		FieldHook:  defaultFieldMutateHook,
 	}
 	require.NoError(t, p.MutateConfig(cfg))
 
@@ -77,6 +75,8 @@ func TestModelGeneration(t *testing.T) {
 		expectedTags := []string{
 			`json:"name" anotherTag:"tag"`,
 			`json:"enum" yetAnotherTag:"12"`,
+			`json:"noVal" yaml:"noVal"`,
+			`json:"repeated" someTag:"value" repeated:"true"`,
 		}
 
 		for _, tag := range expectedTags {
@@ -98,19 +98,3 @@ func mutateHook(b *ModelBuild) *ModelBuild {
 
 	return b
 }
-
-func mutateFieldHook(td *ast.Definition, fd *ast.FieldDefinition, f *Field) (*Field, error) {
-
-	if fd.Directives == nil || td.Name != "FieldMutationHook" {
-		return f, nil
-	}
-
-	directive := fd.Directives.ForName("addTag")
-	if directive != nil {
-		args := directive.ArgumentMap(map[string]interface{}{})
-		if tag, ok := args["tag"]; ok {
-			f.Tag += " " + tag.(string)
-		}
-	}
-	return f, nil
-}

plugin/modelgen/testdata/schema.graphql

@@ -1,5 +1,7 @@
-directive @addTag(tag: String!) on INPUT_FIELD_DEFINITION
-    | FIELD_DEFINITION
+directive @goTag(
+    key: String!
+    value: String
+) on INPUT_FIELD_DEFINITION | FIELD_DEFINITION
 
 type Query {
     thisShoudlntGetGenerated: Boolean
@@ -58,8 +60,11 @@ input ExistingInput {
 }
 
 type FieldMutationHook {
-    name: String @addTag(tag :"anotherTag:\"tag\"")
-    enum: ExistingEnum @addTag(tag: "yetAnotherTag:\"12\"")
+    name: String @goTag(key :"anotherTag", value: "tag")
+    enum: ExistingEnum @goTag(key: "yetAnotherTag", value: "12")
+    noVal: String @goTag(key: "yaml") @goTag(key : "repeated", value: "true")
+    repeated: String @goTag(key: "someTag", value: "value") @goTag(key : "repeated", value: "true")
+
 }
 
 enum ExistingEnum {