dagger/dagger · error

failed to generate type def code for %s: %w

Error message

failed to generate type def code for %s: %w

What it means

Wrapping error from the StructVisitor in moduleMainSrc: after successfully generating implementation code, producing the object's TypeDefCode (the dag.TypeDef().WithObject(...) registration statement) failed. The object name is included; the true cause is wrapped with %w and comes from the type's TypeDef generation.

Source

Thrown at cmd/codegen/generator/go/templates/modules.go:163

				}
				return nil
			},
			StructVisitor: func(ps *parseState, named *types.Named, obj *types.TypeName, objTypeSpec *parsedObjectType, strct *types.Struct) error {
				if err := ps.fillObjectFunctionCases(named, objFunctionCases); err != nil {
					// errors indicate an internal problem rather than something w/ user code, so error instead
					return fmt.Errorf("failed to generate function cases for %s: %w", obj.Name(), err)
				}

				// Add the object to the module
				implCode, err := objTypeSpec.ImplementationCode()
				if err != nil {
					return fmt.Errorf("failed to generate json method code for %s: %w", obj.Name(), err)
				}
				implementationCode.Add(implCode).Line()

				objTypeDefCode, err := objTypeSpec.TypeDefCode()
				if err != nil {
					return fmt.Errorf("failed to generate type def code for %s: %w", obj.Name(), err)
				}
				createMod = dotLine(createMod, "WithObject").Call(Add(Line(), objTypeDefCode))

				return nil
			},
			IfaceVisitor: func(ps *parseState, named *types.Named, obj *types.TypeName, ifaceTypeSpec *parsedIfaceType, iface *types.Interface) error {
				// Add the iface to the module
				implCode, err := ifaceTypeSpec.ImplementationCode()
				if err != nil {
					return fmt.Errorf("failed to generate concrete struct code for %s: %w", obj.Name(), err)
				}
				implementationCode.Add(implCode).Line()

				ifaceTypeDefCode, err := ifaceTypeSpec.TypeDefCode()
				if err != nil {
					return fmt.Errorf("failed to generate type def code for %s: %w", obj.Name(), err)
				}
				createMod = dotLine(createMod, "WithInterface").Call(Add(Line(), ifaceTypeDefCode))

View on GitHub (pinned to 82ba2681db)

Solutions

1. Read the wrapped cause to identify the failing field or sub-type.
2. Change the offending field to a supported Dagger type (named struct, primitive, slice, enum, scalar).
3. Regenerate dagger.gen.go via `dagger develop` and confirm the module compiles; upgrade CLI/SDK if this persists on valid code.

Example fix

// before
type Cache struct {
	Entries map[string]Entry
}

// after
type Cache struct {
	Entries []Entry // or []EntryKeyVal with Key/Value fields
}

// Pre-validate that all object field types map to Dagger TypeDef kinds.
func validateTypeDefFields(t reflect.Type) error {
	for i := 0; i < t.NumField(); i++ {
		ft := t.Field(i).Type
		if ft.Kind() == reflect.Map || ft.Kind() == reflect.Chan || ft.Kind() == reflect.Func {
			return fmt.Errorf("%s.%s (%v) has no TypeDef mapping", t.Name(), t.Field(i).Name, ft)
		}
	}
	return nil
}

if err := codegen(); err != nil && strings.Contains(err.Error(), "failed to generate type def code") {
	log.Fatalf("typedef generation failed: %v", errors.Unwrap(err))
}

When it happens

Trigger: objTypeSpec.TypeDefCode() errors while building the TypeDef for a module object — usually a field whose type reference cannot be converted to a TypeDef (unsupported basic type, anonymous composite, nested failure via slices).

Common situations: Objects containing fields with exotic Go types, deeply nested unsupported composites, or broken references to types from dependent modules.

Related errors

• could not encode default value %q: %w
• expected struct type for %s
• unexpected context type in inline field %s
• unexpected context type for arg %s
• nested structs are not supported

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/1d2f862163c14bc7. Report an issue: GitHub.