Add vendor extensions support for fields.

README.md

@@ -117,6 +117,7 @@ These apply to specifically marked fields, giving you more finely-grained contro
 
 - [ignore](internal/converter/testdata/proto/OptionIgnoredField.proto): Ignore (omit) a specific field
 - [required](internal/converter/testdata/proto/OptionRequiredField.proto): Mark a specific field as being REQUIRED
+- [vendor_ext](internal/converter/testdata/proto/OptionVendorExtension.proto): Add custom "vendor extension" alongside field definition
 
 ### File Options
 
@@ -152,6 +153,13 @@ At the moment the following are supported (but export more in the future):
     - Pattern
 
 
+Vendor Extensions
+-----------------
+JSON schemas support the addition of user-defined fields, commonly referred to as "vendor extensions." These extensions allow for the inclusion of custom keys that JSON schema processors can handle specifically. This feature is particularly beneficial when used in conjunction with OpenAPI specifications. Tools like the openapi-generator can recognize these vendor extensions and incorporate them into the generated code, depending on the capabilities of the specific code generator.
+
+Currently, the option to include these extensions is supported only at the field level.
+
+
 Examples
 --------
 

internal/converter/converter_test.go

@@ -423,6 +423,11 @@ func configureSampleProtos() map[string]sampleProto {
 			ObjectsToValidateFail: []string{testdata.OptionRequiredMessageFail},
 			ObjectsToValidatePass: []string{testdata.OptionRequiredMessagePass},
 		},
+		"OptionVendorExtension": {
+			ExpectedJSONSchema: []string{testdata.OptionVendorExtension},
+			FilesToGenerate:    []string{"OptionVendorExtension.proto"},
+			ProtoFileName:      "OptionVendorExtension.proto",
+		},
 		"PackagePrefix": {
 			Flags:                 ConverterFlags{PrefixSchemaFilesWithPackage: true},
 			ExpectedJSONSchema:    []string{testdata.Timestamp},

internal/converter/testdata/option_vendor_extension.go

@@ -0,0 +1,22 @@
+package testdata
+
+const OptionVendorExtension = `{
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "$ref": "#/definitions/OptionVendorExtension",
+    "definitions": {
+        "OptionVendorExtension": {
+            "properties": {
+                "query": {
+                    "type": "string",
+                    "x-go-custom-tag": "validate:\"required\""
+                },
+                "result_per_page": {
+                    "type": "integer"
+                }
+            },
+            "additionalProperties": true,
+            "type": "object",
+            "title": "Option Vendor Extension"
+        }
+    }
+}`

internal/converter/testdata/proto/OptionVendorExtension.proto

@@ -0,0 +1,8 @@
+syntax = "proto3";
+package samples;
+import "options.proto";
+
+message OptionVendorExtension {
+  string query = 1 [(protoc.gen.jsonschema.field_options).vendor_ext = {key: "x-go-custom-tag" value: 'validate:"required"'}];
+  int32 result_per_page = 3;
+}

internal/converter/types.go

@@ -408,9 +408,9 @@ func (c *Converter) convertMessageType(curPkg *ProtoPackage, msgDesc *descriptor
 	for refmsgDesc, nameWithPackage := range duplicatedMessages {
 		var typeName string
 		if c.Flags.TypeNamesWithNoPackage {
-			typeName = refmsgDesc.GetName();
+			typeName = refmsgDesc.GetName()
 		} else {
-			typeName = nameWithPackage;
+			typeName = nameWithPackage
 		}
 		refType, err := c.recursiveConvertMessageType(curPkg, refmsgDesc, "", duplicatedMessages, true)
 		if err != nil {
@@ -577,9 +577,9 @@ func (c *Converter) recursiveConvertMessageType(curPkg *ProtoPackage, msgDesc *d
 	if nameWithPackage, ok := duplicatedMessages[msgDesc]; ok && !ignoreDuplicatedMessages {
 		var typeName string
 		if c.Flags.TypeNamesWithNoPackage {
-			typeName = msgDesc.GetName();
+			typeName = msgDesc.GetName()
 		} else {
-			typeName = nameWithPackage;
+			typeName = nameWithPackage
 		}
 		return &jsonschema.Type{
 			Ref: fmt.Sprintf("%s%s", c.refPrefix, typeName),
@@ -606,6 +606,7 @@ func (c *Converter) recursiveConvertMessageType(curPkg *ProtoPackage, msgDesc *d
 	c.logger.WithField("message_str", msgDesc.String()).Trace("Converting message")
 	for _, fieldDesc := range msgDesc.GetField() {
 
+		var vendorExtension map[string]interface{}
 		// Custom field options from protoc-gen-jsonschema:
 		if opt := proto.GetExtension(fieldDesc.GetOptions(), protoc_gen_jsonschema.E_FieldOptions); opt != nil {
 			if fieldOptions, ok := opt.(*protoc_gen_jsonschema.FieldOptions); ok {
@@ -625,6 +626,13 @@ func (c *Converter) recursiveConvertMessageType(curPkg *ProtoPackage, msgDesc *d
 						jsonSchemaType.Required = append(jsonSchemaType.Required, fieldDesc.GetName())
 					}
 				}
+
+				// "Vendor Extension" is passed to the generated json schema:
+				if fieldOptions.GetVendorExt() != nil {
+					vendorExt := fieldOptions.GetVendorExt()
+					c.logger.WithField("field_name", fieldDesc.GetName()).WithField("message_name", msgDesc.GetName()).Debug("Adding vendor extension: {}", vendorExt)
+					vendorExtension = vendorExtensionToExtras(vendorExt)
+				}
 			}
 		}
 
@@ -634,6 +642,7 @@ func (c *Converter) recursiveConvertMessageType(curPkg *ProtoPackage, msgDesc *d
 			c.logger.WithError(err).WithField("field_name", fieldDesc.GetName()).WithField("message_name", msgDesc.GetName()).Error("Failed to convert field")
 			return nil, err
 		}
+		recursedJSONSchemaType.Extras = vendorExtension
 		c.logger.WithField("field_name", fieldDesc.GetName()).WithField("type", recursedJSONSchemaType.Type).Trace("Converted field")
 
 		// If this field is part of a OneOf declaration then build that here:
@@ -697,6 +706,15 @@ func (c *Converter) recursiveConvertMessageType(curPkg *ProtoPackage, msgDesc *d
 	return jsonSchemaType, nil
 }
 
+func vendorExtensionToExtras(vendorExt *protoc_gen_jsonschema.VendorExtension) map[string]interface{} {
+	if vendorExt == nil {
+		return nil
+	}
+	extras := make(map[string]interface{})
+	extras[vendorExt.GetKey()] = vendorExt.GetValue()
+	return extras
+}
+
 func dedupe(inputStrings []string) []string {
 	appended := make(map[string]bool)
 	outputStrings := []string{}