Improve deepobject unmarshalling to support nullable.Nullable and encode.TextUnmarshaler (#45)

* Add deepobject tests for more complex types

Specifically, types that there are special edge-cases for

* Add deepobject support for test unmarshalers

* Make deepobject support nullable values

* Strip nullable support, fix TextUnmarshaler placement

Remove nullable.Nullable deep object support (moved to separate repo).
Move TextUnmarshaler check into case reflect.Struct after the legacy
Date/time.Time handlers, so it catches types like uuid.UUID without
intercepting time.Time date-only fallback parsing. Add early returns
to the Date and time.Time blocks which previously fell through.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: James Waters <jcw@netcraft.com>
Co-authored-by: Marcin Romaszewicz <marcinr@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 4 people

deepobject.go

@@ -2,6 +2,7 @@ package runtime
 
 import (
 	"bytes"
+	"encoding"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -55,8 +56,16 @@ func marshalDeepObject(in interface{}, path []string) ([]string, error) {
 		// into a deepObject style set of subscripts. [a, b, c] turns into
 		// [a][b][c]
 		prefix := "[" + strings.Join(path, "][") + "]"
+
+		var value string
+		if t == nil {
+			value = "null"
+		} else {
+			value = fmt.Sprintf("%v", t)
+		}
+
 		result = []string{
-			prefix + fmt.Sprintf("=%v", t),
+			prefix + fmt.Sprintf("=%s", value),
 		}
 	}
 	return result, nil
@@ -268,6 +277,7 @@ func assignPathValues(dst interface{}, pathValues fieldOrValue) error {
 				dst = reflect.Indirect(aPtr)
 			}
 			dst.Set(reflect.ValueOf(date))
+			return nil
 		}
 		if it.ConvertibleTo(reflect.TypeOf(time.Time{})) {
 			var tm time.Time
@@ -288,6 +298,13 @@ func assignPathValues(dst interface{}, pathValues fieldOrValue) error {
 				dst = reflect.Indirect(aPtr)
 			}
 			dst.Set(reflect.ValueOf(tm))
+			return nil
+		}
+		// For other struct types that implement TextUnmarshaler (e.g. uuid.UUID),
+		// use that for binding. This comes after the legacy Date/time.Time checks
+		// above which have special fallback format handling.
+		if tu, ok := v.Interface().(encoding.TextUnmarshaler); ok {
+			return tu.UnmarshalText([]byte(pathValues.value))
 		}
 		fieldMap, err := fieldIndicesByJSONTag(iv.Interface())
 		if err != nil {

deepobject_test.go

@@ -63,6 +63,7 @@ func TestDeepObject(t *testing.T) {
 	om := map[string]int{
 		"additional": 1,
 	}
+
 	d := MockBinder{Time: time.Date(2020, 2, 1, 0, 0, 0, 0, time.UTC)}
 
 	two := 2