oapi-codegen · deepmap-marcinr · Jul 28, 2023 · Jun 10, 2023 · Jun 11, 2023
diff --git a/README.md b/README.md
@@ -568,6 +568,20 @@ which help you to use the various OpenAPI 3 Authentication mechanism.
   will override any default value. This extended property isn't supported in all parts of
   OpenAPI, so please refer to the spec as to where it's allowed. Swagger validation tools will
   flag incorrect usage of this property.
+- `x-go-type-skip-optional-pointer`: specifies if the Go type should or should not be a pointer
+  when the property is optional. If set to true, the type will not be a pointer if the field is
+  optional or nullable. If set to false, the type will be a pointer.
+
+  ```yaml
+  properties:
+    field:
+      type: string
+      x-go-type-skip-optional-pointer: true
+  ```
+
+  In the example above, the `field` field will be of type `string` instead of `*string`. This is
+  useful when you want to handle the case of an empty string differently than a null value.
+
 - `x-go-name`: specifies Go field name. It allows you to specify the field name for a schema, and
   will override any default value. This extended property isn't supported in all parts of
   OpenAPI, so please refer to the spec as to where it's allowed. Swagger validation tools will

diff --git a/pkg/codegen/codegen_test.go b/pkg/codegen/codegen_test.go
@@ -10,13 +10,14 @@ import (
 	"net/http"
 	"testing"
 
-	examplePetstoreClient "github.com/deepmap/oapi-codegen/examples/petstore-expanded"
-	examplePetstore "github.com/deepmap/oapi-codegen/examples/petstore-expanded/echo/api"
-	"github.com/deepmap/oapi-codegen/pkg/util"
 	"github.com/getkin/kin-openapi/openapi3"
 	"github.com/golangci/lint-1"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	examplePetstoreClient "github.com/deepmap/oapi-codegen/examples/petstore-expanded"
+	examplePetstore "github.com/deepmap/oapi-codegen/examples/petstore-expanded/echo/api"
+	"github.com/deepmap/oapi-codegen/pkg/util"
 )
 
 const (
@@ -156,7 +157,7 @@ func TestExamplePetStoreCodeGenerationWithHTTPUserTemplates(t *testing.T) {
 	defer ln.Close()
 
 	//nolint:errcheck
-	//Does not matter if the server returns an error on close etc.
+	// Does not matter if the server returns an error on close etc.
 	go http.Serve(ln, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		_, writeErr := w.Write([]byte("//blah"))
 		assert.NoError(t, writeErr)
@@ -288,6 +289,44 @@ type GetTestByNameResponse struct {
 	checkLint(t, "test.gen.go", []byte(code))
 }
 
+func TestExtPropGoTypeSkipOptionalPointer(t *testing.T) {
+	packageName := "api"
+	opts := Configuration{
+		PackageName: packageName,
+		Generate: GenerateOptions{
+			EchoServer:   true,
+			Models:       true,
+			EmbeddedSpec: true,
+			Strict:       true,
+		},
+	}
+	spec := "test_specs/x-go-type-skip-optional-pointer.yaml"
+	swagger, err := util.LoadSwagger(spec)
+	require.NoError(t, err)
+
+	// Run our code generation:
+	code, err := Generate(swagger, opts)
+	assert.NoError(t, err)
+	assert.NotEmpty(t, code)
+
+	// Check that we have valid (formattable) code:
+	_, err = format.Source([]byte(code))
+	assert.NoError(t, err)
+
+	// Check that optional pointer fields are skipped if requested
+	assert.Contains(t, code, "NullableFieldSkipFalse *string `json:\"nullableFieldSkipFalse\"`")
+	assert.Contains(t, code, "NullableFieldSkipTrue  string  `json:\"nullableFieldSkipTrue\"`")
+	assert.Contains(t, code, "OptionalField          *string `json:\"optionalField,omitempty\"`")
+	assert.Contains(t, code, "OptionalFieldSkipFalse *string `json:\"optionalFieldSkipFalse,omitempty\"`")
+	assert.Contains(t, code, "OptionalFieldSkipTrue  string  `json:\"optionalFieldSkipTrue,omitempty\"`")
+
+	// Check that the extension applies on custom types as well
+	assert.Contains(t, code, "CustomTypeWithSkipTrue string  `json:\"customTypeWithSkipTrue,omitempty\"`")
+
+	// Check that the extension has no effect on required fields
+	assert.Contains(t, code, "RequiredField          string  `json:\"requiredField\"`")
+}
+
 func TestGoTypeImport(t *testing.T) {
 	packageName := "api"
 	opts := Configuration{

diff --git a/pkg/codegen/extension.go b/pkg/codegen/extension.go
@@ -7,6 +7,9 @@ import (
 const (
 	// extPropGoType overrides the generated type definition.
 	extPropGoType = "x-go-type"
+	// extPropGoTypeSkipOptionalPointer specifies that optional fields should
+	// be the type itself instead of a pointer to the type.
+	extPropGoTypeSkipOptionalPointer = "x-go-type-skip-optional-pointer"
 	// extPropGoImport specifies the module to import which provides above type
 	extPropGoImport = "x-go-type-import"
 	// extGoName is used to override a field name
@@ -28,10 +31,19 @@ func extString(extPropValue interface{}) (string, error) {
 	}
 	return str, nil
 }
+
 func extTypeName(extPropValue interface{}) (string, error) {
 	return extString(extPropValue)
 }
 
+func extParsePropGoTypeSkipOptionalPointer(extPropValue interface{}) (bool, error) {
+	goTypeSkipOptionalPointer, ok := extPropValue.(bool)
+	if !ok {
+		return false, fmt.Errorf("failed to convert type: %T", extPropValue)
+	}
+	return goTypeSkipOptionalPointer, nil
+}
+
 func extParseGoFieldName(extPropValue interface{}) (string, error) {
 	return extString(extPropValue)
 }

diff --git a/pkg/codegen/extension_test.go b/pkg/codegen/extension_test.go
@@ -54,3 +54,57 @@ func Test_extTypeName(t *testing.T) {
 		})
 	}
 }
+
+func Test_extParsePropGoTypeSkipOptionalPointer(t *testing.T) {
+	type args struct {
+		extPropValue json.RawMessage
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    bool
+		wantErr bool
+	}{
+		{
+			name:    "success when set to true",
+			args:    args{json.RawMessage(`true`)},
+			want:    true,
+			wantErr: false,
+		},
+		{
+			name:    "success when set to false",
+			args:    args{json.RawMessage(`false`)},
+			want:    false,
+			wantErr: false,
+		},
+		{
+			name:    "nil conversion error",
+			args:    args{nil},
+			want:    false,
+			wantErr: true,
+		},
+		{
+			name:    "type conversion error",
+			args:    args{json.RawMessage(`"true"`)},
+			want:    false,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// kin-openapi no longer returns these as RawMessage
+			var extPropValue interface{}
+			if tt.args.extPropValue != nil {
+				err := json.Unmarshal(tt.args.extPropValue, &extPropValue)
+				assert.NoError(t, err)
+			}
+			got, err := extParsePropGoTypeSkipOptionalPointer(extPropValue)
+			if tt.wantErr {
+				assert.Error(t, err)
+				return
+			}
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, got)
+		})
+	}
+}
diff --git a/pkg/codegen/schema.go b/pkg/codegen/schema.go
@@ -276,6 +276,16 @@ func GenerateGoSchema(sref *openapi3.SchemaRef, path []string) (Schema, error) {
 		return outSchema, nil
 	}
 
+	// Check x-go-type-skip-optional-pointer, which will override if the type
+	// should be a pointer or not when the field is optional.
+	if extension, ok := schema.Extensions[extPropGoTypeSkipOptionalPointer]; ok {
+		skipOptionalPointer, err := extParsePropGoTypeSkipOptionalPointer(extension)
+		if err != nil {
+			return outSchema, fmt.Errorf("invalid value for %q: %w", extPropGoTypeSkipOptionalPointer, err)
+		}
+		outSchema.SkipOptionalPointer = skipOptionalPointer
+	}
+
 	// Schema type and format, eg. string / binary
 	t := schema.Type
 	// Handle objects and empty schemas first as a special case
@@ -661,6 +671,14 @@ func GenFieldsFromProperties(props []Property) []string {
 			field += fmt.Sprintf("%s\n", DeprecationComment(deprecationReason))
 		}
 
+		// Check x-go-type-skip-optional-pointer, which will override if the type
+		// should be a pointer or not when the field is optional.
+		if extension, ok := p.Extensions[extPropGoTypeSkipOptionalPointer]; ok {
+			if skipOptionalPointer, err := extParsePropGoTypeSkipOptionalPointer(extension); err == nil {
+				p.Schema.SkipOptionalPointer = skipOptionalPointer
+			}
+		}
+
 		field += fmt.Sprintf("    %s %s", goFieldName, p.GoTypeDef())
 
 		omitEmpty := !p.Nullable &&

diff --git a/pkg/codegen/test_specs/x-go-type-skip-optional-pointer.yaml b/pkg/codegen/test_specs/x-go-type-skip-optional-pointer.yaml
@@ -0,0 +1,54 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Example with x-go-type-skip-optional-pointer
+paths:
+  /check:
+    get:
+      summary: Return example
+      responses:
+        '200':
+          description: Ok
+          content:
+            application/json:
+              schema:
+                required:
+                  - requiredField
+                properties:
+                  # Optional field where the type is a pointer to a string, and
+                  # the x-go-type-skip-optional-pointer is not set.
+                  optionalField:
+                    type: string
+                  # Optional field where the type is a pointer to a string, and
+                  # the x-go-type-skip-optional-pointer is set to false.
+                  optionalFieldSkipFalse:
+                    type: string
+                    x-go-type-skip-optional-pointer: false
+                  # Optional field where the type is a pointer to a string, and
+                  # the x-go-type-skip-optional-pointer is set to true.
+                  optionalFieldSkipTrue:
+                      type: string
+                      x-go-type-skip-optional-pointer: true
+                  # Optional field where the type is a pointer to a string, and
+                  # the x-go-type-skip-optional-pointer is set to true.
+                  customTypeWithSkipTrue:
+                    type: string
+                    x-go-type: string
+                    x-go-type-skip-optional-pointer: true
+                  # Nullable field where the type is a pointer to a string, and
+                  # the x-go-type-skip-optional-pointer is set to false.
+                  nullableFieldSkipFalse:
+                    type: string
+                    nullable: true
+                    x-go-type-skip-optional-pointer: false
+                  # Nullable field where the type is a pointer to a string, and
+                  # the x-go-type-skip-optional-pointer is set to true.
+                  nullableFieldSkipTrue:
+                    type: string
+                    nullable: true
+                    x-go-type-skip-optional-pointer: true
+                  # Check that x-go-type-skip-optional-pointer has no effect on
+                  # required fields.
+                  requiredField:
+                    type: string
+                    x-go-type-skip-optional-pointer: false