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schema.go
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schema.go
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package rest
import (
"fmt"
"reflect"
"slices"
"sort"
"strings"
"github.com/a-h/rest/enums"
"github.com/a-h/rest/getcomments/parser"
"github.com/getkin/kin-openapi/openapi3"
"golang.org/x/exp/constraints"
)
func newSpec(name string) *openapi3.T {
return &openapi3.T{
OpenAPI: "3.0.0",
Info: &openapi3.Info{
Title: name,
Version: "0.0.0",
Extensions: map[string]interface{}{},
},
Components: &openapi3.Components{
Schemas: make(openapi3.Schemas),
Extensions: map[string]interface{}{},
},
Paths: &openapi3.Paths{},
Extensions: map[string]interface{}{},
}
}
func getSortedKeys[V any](m map[string]V) (op []string) {
for k := range m {
op = append(op, k)
}
sort.Slice(op, func(i, j int) bool {
return op[i] < op[j]
})
return op
}
func newPrimitiveSchema(paramType PrimitiveType) *openapi3.Schema {
switch paramType {
case PrimitiveTypeString:
return openapi3.NewStringSchema()
case PrimitiveTypeBool:
return openapi3.NewBoolSchema()
case PrimitiveTypeInteger:
return openapi3.NewIntegerSchema()
case PrimitiveTypeFloat64:
return openapi3.NewFloat64Schema()
case "":
return openapi3.NewStringSchema()
default:
return &openapi3.Schema{
Type: &openapi3.Types{string(paramType)},
}
}
}
func (api *API) createOpenAPI() (spec *openapi3.T, err error) {
spec = newSpec(api.Name)
// Add all the routes.
for pattern, methodToRoute := range api.Routes {
path := &openapi3.PathItem{}
for method, route := range methodToRoute {
op := &openapi3.Operation{}
// Add the query params.
for _, k := range getSortedKeys(route.Params.Query) {
v := route.Params.Query[k]
ps := newPrimitiveSchema(v.Type).
WithPattern(v.Regexp)
queryParam := openapi3.NewQueryParameter(k).
WithDescription(v.Description).
WithSchema(ps)
queryParam.Required = v.Required
queryParam.AllowEmptyValue = v.AllowEmpty
// Apply schema customisation.
if v.ApplyCustomSchema != nil {
v.ApplyCustomSchema(queryParam)
}
op.AddParameter(queryParam)
}
// Add the route params.
for _, k := range getSortedKeys(route.Params.Path) {
v := route.Params.Path[k]
ps := newPrimitiveSchema(v.Type).
WithPattern(v.Regexp)
pathParam := openapi3.NewPathParameter(k).
WithDescription(v.Description).
WithSchema(ps)
// Apply schema customisation.
if v.ApplyCustomSchema != nil {
v.ApplyCustomSchema(pathParam)
}
op.AddParameter(pathParam)
}
// Handle request types.
if route.Models.Request.Type != nil {
name, schema, err := api.RegisterModel(route.Models.Request)
if err != nil {
return spec, err
}
op.RequestBody = &openapi3.RequestBodyRef{
Value: openapi3.NewRequestBody().WithContent(map[string]*openapi3.MediaType{
"application/json": {
Schema: getSchemaReferenceOrValue(name, schema),
},
}),
}
}
// Handle response types.
for status, model := range route.Models.Responses {
name, schema, err := api.RegisterModel(model)
if err != nil {
return spec, err
}
resp := openapi3.NewResponse().
WithDescription("").
WithContent(map[string]*openapi3.MediaType{
"application/json": {
Schema: getSchemaReferenceOrValue(name, schema),
},
})
op.AddResponse(status, resp)
}
// Handle tags.
op.Tags = append(op.Tags, route.Tags...)
// Handle OperationID.
op.OperationID = route.OperationID
// Handle description.
op.Description = route.Description
// Register the method.
path.SetOperation(string(method), op)
}
// Populate the OpenAPI schemas from the models.
for name, schema := range api.models {
spec.Components.Schemas[name] = openapi3.NewSchemaRef("", schema)
}
spec.Paths.Set(string(pattern), path)
}
loader := openapi3.NewLoader()
if err = loader.ResolveRefsIn(spec, nil); err != nil {
return spec, fmt.Errorf("failed to resolve, due to external references: %w", err)
}
if err = spec.Validate(loader.Context); err != nil {
return spec, fmt.Errorf("failed validation: %w", err)
}
return spec, err
}
func (api *API) getModelName(t reflect.Type) string {
pkgPath, typeName := t.PkgPath(), t.Name()
if t.Kind() == reflect.Pointer {
pkgPath = t.Elem().PkgPath()
typeName = t.Elem().Name() + "Ptr"
}
if t.Kind() == reflect.Map {
typeName = fmt.Sprintf("map[%s]%s", t.Key().Name(), t.Elem().Name())
}
schemaName := api.normalizeTypeName(pkgPath, typeName)
if typeName == "" {
schemaName = fmt.Sprintf("AnonymousType%d", len(api.models))
}
return schemaName
}
func getSchemaReferenceOrValue(name string, schema *openapi3.Schema) *openapi3.SchemaRef {
if shouldBeReferenced(schema) {
return openapi3.NewSchemaRef(fmt.Sprintf("#/components/schemas/%s", name), nil)
}
return openapi3.NewSchemaRef("", schema)
}
// ModelOpts defines options that can be set when registering a model.
type ModelOpts func(s *openapi3.Schema)
// WithNullable sets the nullable field to true.
func WithNullable() ModelOpts {
return func(s *openapi3.Schema) {
s.Nullable = true
}
}
// WithDescription sets the description field on the schema.
func WithDescription(desc string) ModelOpts {
return func(s *openapi3.Schema) {
s.Description = desc
}
}
// WithEnumValues sets the property to be an enum value with the specific values.
func WithEnumValues[T ~string | constraints.Integer](values ...T) ModelOpts {
return func(s *openapi3.Schema) {
if len(values) == 0 {
return
}
s.Type = &openapi3.Types{openapi3.TypeString}
if reflect.TypeOf(values[0]).Kind() != reflect.String {
s.Type = &openapi3.Types{openapi3.TypeInteger}
}
for _, v := range values {
s.Enum = append(s.Enum, v)
}
}
}
// WithEnumConstants sets the property to be an enum containing the values of the type found in the package.
func WithEnumConstants[T ~string | constraints.Integer]() ModelOpts {
return func(s *openapi3.Schema) {
var t T
ty := reflect.TypeOf(t)
s.Type = &openapi3.Types{openapi3.TypeString}
if ty.Kind() != reflect.String {
s.Type = &openapi3.Types{openapi3.TypeInteger}
}
enum, err := enums.Get(ty)
if err != nil {
panic(err)
}
s.Enum = enum
}
}
func isFieldRequired(isPointer, hasOmitEmpty bool) bool {
return !(isPointer || hasOmitEmpty)
}
func isMarkedAsDeprecated(comment string) bool {
// A field is only marked as deprecated if a paragraph (line) begins with Deprecated.
// https://github.com/golang/go/wiki/Deprecated
for _, line := range strings.Split(comment, "\n") {
if strings.HasPrefix(strings.TrimSpace(line), "Deprecated:") {
return true
}
}
return false
}
// RegisterModel allows a model to be registered manually so that additional configuration can be applied.
// The schema returned can be modified as required.
func (api *API) RegisterModel(model Model, opts ...ModelOpts) (name string, schema *openapi3.Schema, err error) {
// Get the name.
t := model.Type
name = api.getModelName(t)
// If we've already got the schema, return it.
var ok bool
if schema, ok = api.models[name]; ok {
return name, schema, nil
}
// It's known, but not in the schemaset yet.
if knownSchema, ok := api.KnownTypes[t]; ok {
// Objects, enums, need to be references, so add it into the
// list.
if shouldBeReferenced(&knownSchema) {
api.models[name] = &knownSchema
}
return name, &knownSchema, nil
}
var elementName string
var elementSchema *openapi3.Schema
switch t.Kind() {
case reflect.Slice, reflect.Array:
elementName, elementSchema, err = api.RegisterModel(modelFromType(t.Elem()))
if err != nil {
return name, schema, fmt.Errorf("error getting schema of slice element %v: %w", t.Elem(), err)
}
schema = openapi3.NewArraySchema().WithNullable() // Arrays are always nilable in Go.
schema.Items = getSchemaReferenceOrValue(elementName, elementSchema)
case reflect.String:
schema = openapi3.NewStringSchema()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
schema = openapi3.NewIntegerSchema()
case reflect.Float64, reflect.Float32:
schema = openapi3.NewFloat64Schema()
case reflect.Bool:
schema = openapi3.NewBoolSchema()
case reflect.Pointer:
name, schema, err = api.RegisterModel(modelFromType(t.Elem()), WithNullable())
case reflect.Map:
// Check that the key is a string.
if t.Key().Kind() != reflect.String {
return name, schema, fmt.Errorf("maps must have a string key, but this map is of type %q", t.Key().String())
}
// Get the element schema.
elementName, elementSchema, err = api.RegisterModel(modelFromType(t.Elem()))
if err != nil {
return name, schema, fmt.Errorf("error getting schema of map value element %v: %w", t.Elem(), err)
}
schema = openapi3.NewObjectSchema().WithNullable()
schema.AdditionalProperties.Schema = getSchemaReferenceOrValue(elementName, elementSchema)
case reflect.Struct:
schema = openapi3.NewObjectSchema()
if schema.Description, schema.Deprecated, err = api.getTypeComment(t.PkgPath(), t.Name()); err != nil {
return name, schema, fmt.Errorf("failed to get comments for type %q: %w", name, err)
}
schema.Properties = make(openapi3.Schemas)
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
if !f.IsExported() {
continue
}
// Get JSON fieldName.
jsonTags := strings.Split(f.Tag.Get("json"), ",")
fieldName := jsonTags[0]
if fieldName == "" {
fieldName = f.Name
}
// If the model doesn't exist.
_, alreadyExists := api.models[api.getModelName(f.Type)]
fieldSchemaName, fieldSchema, err := api.RegisterModel(modelFromType(f.Type))
if err != nil {
return name, schema, fmt.Errorf("error getting schema for type %q, field %q, failed to get schema for embedded type %q: %w", t, fieldName, f.Type, err)
}
if f.Anonymous {
// It's an anonymous type, no need for a reference to it,
// since we're copying the fields.
if !alreadyExists {
delete(api.models, fieldSchemaName)
}
// Add all embedded fields to this type.
for name, ref := range fieldSchema.Properties {
schema.Properties[name] = ref
}
schema.Required = append(schema.Required, fieldSchema.Required...)
continue
}
ref := getSchemaReferenceOrValue(fieldSchemaName, fieldSchema)
if ref.Value != nil {
if ref.Value.Description, ref.Value.Deprecated, err = api.getTypeFieldComment(t.PkgPath(), t.Name(), f.Name); err != nil {
return name, schema, fmt.Errorf("failed to get comments for field %q in type %q: %w", fieldName, name, err)
}
}
schema.Properties[fieldName] = ref
isPtr := f.Type.Kind() == reflect.Pointer
hasOmitEmptySet := slices.Contains(jsonTags, "omitempty")
if isFieldRequired(isPtr, hasOmitEmptySet) {
schema.Required = append(schema.Required, fieldName)
}
}
}
if schema == nil {
return name, schema, fmt.Errorf("unsupported type: %v/%v", t.PkgPath(), t.Name())
}
// Apply global customisation.
if api.ApplyCustomSchemaToType != nil {
api.ApplyCustomSchemaToType(t, schema)
}
// Customise the model using its ApplyCustomSchema method.
// This allows any type to customise its schema.
model.ApplyCustomSchema(schema)
for _, opt := range opts {
opt(schema)
}
// After all processing, register the type if required.
if shouldBeReferenced(schema) {
api.models[name] = schema
return
}
return
}
func (api *API) getCommentsForPackage(pkg string) (pkgComments map[string]string, err error) {
if pkgComments, loaded := api.comments[pkg]; loaded {
return pkgComments, nil
}
pkgComments, err = parser.Get(pkg)
if err != nil {
return
}
api.comments[pkg] = pkgComments
return
}
func (api *API) getTypeComment(pkg string, name string) (comment string, deprecated bool, err error) {
pkgComments, err := api.getCommentsForPackage(pkg)
if err != nil {
return
}
comment = pkgComments[pkg+"."+name]
deprecated = isMarkedAsDeprecated(comment)
return
}
func (api *API) getTypeFieldComment(pkg string, name string, field string) (comment string, deprecated bool, err error) {
pkgComments, err := api.getCommentsForPackage(pkg)
if err != nil {
return
}
comment = pkgComments[pkg+"."+name+"."+field]
deprecated = isMarkedAsDeprecated(comment)
return
}
func shouldBeReferenced(schema *openapi3.Schema) bool {
if schema.Type.Is(openapi3.TypeObject) && schema.AdditionalProperties.Schema == nil {
return true
}
if len(schema.Enum) > 0 {
return true
}
return false
}
var normalizer = strings.NewReplacer("/", "_",
".", "_",
"[", "_",
"]", "_")
func (api *API) normalizeTypeName(pkgPath, name string) string {
var omitPackage bool
for _, pkg := range api.StripPkgPaths {
if strings.HasPrefix(pkgPath, pkg) {
omitPackage = true
break
}
}
if omitPackage || pkgPath == "" {
return normalizer.Replace(name)
}
return normalizer.Replace(pkgPath + "/" + name)
}