[API] Read default value field option and ensure it matches field type

internal/converter/converter_test.go

@@ -316,6 +316,11 @@ func configureSampleProtos() map[string]sampleProto {
 			ObjectsToValidateFail: []string{testdata.OptionAllowNullValuesFail},
 			ObjectsToValidatePass: []string{testdata.OptionAllowNullValuesPass},
 		},
+		"OptionDefaultValue": {
+			ExpectedJSONSchema:    []string{testdata.OptionDefaultValue},
+			FilesToGenerate:       []string{"OptionDefaultValue.proto"},
+			ProtoFileName:         "OptionDefaultValue.proto",
+		},
 		"OptionDisallowAdditionalProperties": {
 			ExpectedJSONSchema:    []string{testdata.OptionDisallowAdditionalProperties},
 			FilesToGenerate:       []string{"OptionDisallowAdditionalProperties.proto"},

internal/converter/jsonschema/reflect.go

@@ -91,6 +91,7 @@ type Type struct {
 	ManualLink           string                 `json:"manualLink,omitempty"`           // custom
 	IgnoreInAutocomplete bool                   `json:"ignoreInAutocomplete,omitempty"` // custom
 	Units                protos.NumericalUnits  `json:"units,omitempty"`                // custom
+	DefaultValue		 interface{}			`json:"DefaultValue,omitempty"`         // custom
 	Not                  *Type                  `json:"not,omitempty"`                  // section 5.25
 	Definitions          Definitions            `json:"definitions,omitempty"`          // section 5.26
 	// RFC draft-wright-json-schema-validation-00, section 6, 7

internal/converter/testdata/option_default_value.go

@@ -0,0 +1,41 @@
+package testdata
+
+const OptionDefaultValue = `{
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "$ref": "#/definitions/OptionDefaultValue",
+    "$fullRef": "#/definitions/samples.OptionDefaultValue",
+    "definitions": {
+        "OptionDefaultValue": {
+            "properties": {
+                "field_one": {
+                    "type": "string",
+                    "options": {
+                        "DefaultValue": "sample_str"
+                    }
+                },
+                "field_two": {
+                    "items": {
+                        "type": "boolean"
+                    },
+                    "type": "array",
+                    "options": {
+                        "DefaultValue": true
+                    }
+                },
+                "field_three": {
+                    "type": "integer",
+                    "options": {
+                        "DefaultValue": 7
+                    }
+                },
+                "field_four": {
+                    "type": "integer"
+                }
+            },
+            "additionalProperties": true,
+            "type": "object",
+            "title": "Option Default Value"
+        }
+    }
+}`
+

internal/converter/testdata/proto/OptionDefaultValue.proto

@@ -0,0 +1,10 @@
+syntax = "proto3";
+package samples;
+import "options.proto";
+
+message OptionDefaultValue {
+    string field_one = 1 [(protoc.gen.jsonschema.default_value).string_value = "sample_str"];
+    repeated bool field_two = 2 [(protoc.gen.jsonschema.default_value).bool_value = true];
+    int32 field_three = 3 [(protoc.gen.jsonschema.default_value).number_value = 7];
+    int32 field_four = 4;
+}

internal/converter/types.go

@@ -12,6 +12,8 @@ import (
 
 	"github.com/AppliedIntuition/protoc-gen-jsonschema/internal/converter/jsonschema"
 	"github.com/AppliedIntuition/protoc-gen-jsonschema/internal/protos"
+
+	"github.com/golang/protobuf/ptypes/struct"
 )
 
 var (
@@ -33,6 +35,20 @@ var (
 	}
 )
 
+// Expected google.protobuf.Value type
+// (this is not 1:1 with protobuf types - for example, doubles and ints
+// are both represented by number_value)
+type ValueType int
+
+// Currently only support overrides for numbers, strings and booleans.
+const (
+	unset			ValueType = iota
+	number_value
+	string_value
+	bool_value
+)
+
+
 func (c *Converter) registerEnum(pkgName string, enum *descriptor.EnumDescriptorProto) {
 	pkg := globalPkg
 	if pkgName != "" {
@@ -114,12 +130,17 @@ func (c *Converter) convertField(curPkg *ProtoPackage, desc *descriptor.FieldDes
 		}
 	}
 
+	// Initialize expectedValueType to unset
+	expectedValueType := unset
+
 	// Switch the types, and pick a JSONSchema equivalent:
 	switch desc.GetType() {
 
 	// Float32:
 	case descriptor.FieldDescriptorProto_TYPE_DOUBLE,
 		descriptor.FieldDescriptorProto_TYPE_FLOAT:
+
+		expectedValueType = number_value
 		if messageFlags.AllowNullValues {
 			jsonSchemaType.OneOf = []*jsonschema.Type{
 				{Type: gojsonschema.TYPE_NULL},
@@ -135,6 +156,8 @@ func (c *Converter) convertField(curPkg *ProtoPackage, desc *descriptor.FieldDes
 		descriptor.FieldDescriptorProto_TYPE_FIXED32,
 		descriptor.FieldDescriptorProto_TYPE_SFIXED32,
 		descriptor.FieldDescriptorProto_TYPE_SINT32:
+
+		expectedValueType = number_value
 		if messageFlags.AllowNullValues {
 			jsonSchemaType.OneOf = []*jsonschema.Type{
 				{Type: gojsonschema.TYPE_NULL},
@@ -150,6 +173,8 @@ func (c *Converter) convertField(curPkg *ProtoPackage, desc *descriptor.FieldDes
 		descriptor.FieldDescriptorProto_TYPE_FIXED64,
 		descriptor.FieldDescriptorProto_TYPE_SFIXED64,
 		descriptor.FieldDescriptorProto_TYPE_SINT64:
+
+		expectedValueType = number_value
 
 		// As integer:
 		if c.Flags.DisallowBigIntsAsStrings {
@@ -177,6 +202,7 @@ func (c *Converter) convertField(curPkg *ProtoPackage, desc *descriptor.FieldDes
 
 	// String:
 	case descriptor.FieldDescriptorProto_TYPE_STRING:
+		expectedValueType = string_value
 		stringDef := &jsonschema.Type{Type: gojsonschema.TYPE_STRING}
 		// Check for custom options
 		opts := desc.GetOptions()
@@ -265,6 +291,7 @@ func (c *Converter) convertField(curPkg *ProtoPackage, desc *descriptor.FieldDes
 
 	// Bool:
 	case descriptor.FieldDescriptorProto_TYPE_BOOL:
+		expectedValueType = bool_value
 		if messageFlags.AllowNullValues {
 			jsonSchemaType.OneOf = []*jsonschema.Type{
 				{Type: gojsonschema.TYPE_NULL},
@@ -308,6 +335,33 @@ func (c *Converter) convertField(curPkg *ProtoPackage, desc *descriptor.FieldDes
 		return nil, fmt.Errorf("unrecognized field type: %s", desc.GetType().String())
 	}
 
+	// Read default_value field option if it exists
+	// and validate that the type matches the field type.
+	if options != nil {
+		if proto.HasExtension(options, protos.E_DefaultValue) {
+			var defaultValue interface{}
+
+			defaultValueObj := proto.GetExtension(options, protos.E_DefaultValue).(*structpb.Value)
+			if defaultValueObj.GetStringValue() != "" && expectedValueType == string_value {
+				defaultValue = defaultValueObj.GetStringValue()
+
+			} else if defaultValueObj.GetBoolValue() != false && expectedValueType == bool_value {
+				defaultValue = defaultValueObj.GetBoolValue()
+
+			} else if defaultValueObj.GetNumberValue() != 0 && expectedValueType == number_value {
+				defaultValue = defaultValueObj.GetNumberValue()
+
+			} else {
+				return nil, fmt.Errorf("Type of default value is incompatible with type of field.")
+			}
+
+			if jsonSchemaType.Options == nil {
+				jsonSchemaType.Options = &jsonschema.Type{}
+			}
+			jsonSchemaType.Options.DefaultValue = defaultValue
+		}
+	}
+
 	// Recurse array of primitive types:
 	if desc.GetLabel() == descriptor.FieldDescriptorProto_LABEL_REPEATED && jsonSchemaType.Type != gojsonschema.TYPE_OBJECT {
 		jsonSchemaType.Items = &jsonschema.Type{}

options.proto

@@ -5,6 +5,7 @@
 syntax = "proto3";
 package protoc.gen.jsonschema;
 import "google/protobuf/descriptor.proto";
+import "google/protobuf/struct.proto";
 option go_package = "./protos";
 
 
@@ -187,6 +188,9 @@ extend google.protobuf.FieldOptions {
   string manual_link = 50015;
   bool ignore_in_autocomplete = 50000;
   NumericalUnits units = 50010;
+
+  // Custom default value of a field
+  google.protobuf.Value default_value = 50019;
 }
 
 extend google.protobuf.FileOptions {