feat: huma.RegisterTypeSchema

schema.go

@@ -14,6 +14,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/danielgtaylor/huma/v2/validation"
@@ -676,6 +677,29 @@ type SchemaTransformer interface {
 	TransformSchema(r Registry, s *Schema) *Schema
 }
 
+type SchemaFactory func(Registry) *Schema
+
+var (
+	schemaFactoryMu sync.RWMutex
+	schemaFactories = map[reflect.Type]SchemaFactory{}
+)
+
+// RegisterTypeSchema associates a schema factory with the given type.
+// The provided factory runs whenever SchemaFromType handles that type.
+// Later calls replace any previously registered factory.
+func RegisterTypeSchema(t reflect.Type, factory SchemaFactory) {
+	if t == nil {
+		panic("huma: RegisterTypeSchema called with nil type")
+	}
+	if factory == nil {
+		panic("huma: RegisterTypeSchema called with nil factory")
+	}
+
+	schemaFactoryMu.Lock()
+	schemaFactories[t] = factory
+	schemaFactoryMu.Unlock()
+}
+
 // SchemaFromType returns a schema for a given type, using the registry to
 // possibly create references for nested structs. The schema that is returned
 // can then be passed to `huma.Validate` to efficiently validate incoming
@@ -699,12 +723,46 @@ func SchemaFromType(r Registry, t reflect.Type) *Schema {
 	return s
 }
 
+func lookupTypeSchemaFactory(t reflect.Type) SchemaFactory {
+	if t == nil {
+		return nil
+	}
+
+	schemaFactoryMu.RLock()
+	factory := schemaFactories[t]
+	schemaFactoryMu.RUnlock()
+	return factory
+}
+
+func schemaFromRegisteredFactory(r Registry, t reflect.Type) *Schema {
+	factory := lookupTypeSchemaFactory(t)
+	if factory == nil {
+		return nil
+	}
+
+	s := factory(r)
+	if s == nil {
+		return nil
+	}
+
+	s.PrecomputeMessages()
+	return s
+}
+
 func schemaFromType(r Registry, t reflect.Type) *Schema {
+	if custom := schemaFromRegisteredFactory(r, t); custom != nil {
+		return custom
+	}
+
 	isPointer := t.Kind() == reflect.Pointer
 
 	s := Schema{}
 	t = deref(t)
 
+	if custom := schemaFromRegisteredFactory(r, t); custom != nil {
+		return custom
+	}
+
 	v := reflect.New(t).Interface()
 	if sp, ok := v.(SchemaProvider); ok {
 		// Special case: type provides its own schema. Do not try to generate.

schema_test.go

@@ -1544,3 +1544,44 @@ func TestSchemaTransformer(t *testing.T) {
 	updateSchema2 := huma.SchemaFromType(r, reflect.TypeOf(ExampleUpdateStruct{}))
 	validateSchema(updateSchema2)
 }
+
+type customSchemaInt int64
+
+func TestRegisterTypeSchema(t *testing.T) {
+	huma.RegisterTypeSchema(reflect.TypeOf(customSchemaInt(0)), func(r huma.Registry) *huma.Schema {
+		return &huma.Schema{Type: huma.TypeString}
+	})
+
+	registry := huma.NewMapRegistry("#/components/schemas/", huma.DefaultSchemaNamer)
+
+	type input struct {
+		ID       customSchemaInt  `json:"id"`
+		Optional *customSchemaInt `json:"optional,omitempty"`
+		Nested   struct {
+			Value customSchemaInt `json:"value"`
+		} `json:"nested"`
+	}
+
+	schema := huma.SchemaFromType(registry, reflect.TypeOf(input{}))
+	require.NotNil(t, schema)
+	require.Contains(t, schema.Properties, "id")
+	assert.Equal(t, huma.TypeString, schema.Properties["id"].Type)
+
+	require.Contains(t, schema.Properties, "optional")
+	assert.Equal(t, huma.TypeString, schema.Properties["optional"].Type)
+
+	nested := schema.Properties["nested"]
+	require.NotNil(t, nested)
+	nestedSchema := nested
+	if nested.Ref != "" {
+		nestedSchema = registry.SchemaFromRef(nested.Ref)
+		require.NotNil(t, nestedSchema)
+	}
+	assert.Equal(t, huma.TypeObject, nestedSchema.Type)
+	require.Contains(t, nestedSchema.Properties, "value")
+	assert.Equal(t, huma.TypeString, nestedSchema.Properties["value"].Type)
+
+	custom := registry.Schema(reflect.TypeOf(customSchemaInt(0)), true, "Standalone")
+	require.NotNil(t, custom)
+	assert.Equal(t, huma.TypeString, custom.Type)
+}