dagger/dagger · error

unexpected context type in inline field %s

Error message

unexpected context type in inline field %s

What it means

When a Dagger function takes a single inline-struct argument, each field of that struct becomes its own exposed argument. A field whose type is context.Context cannot be exposed as an argument, so codegen rejects it with this error naming the offending field.

Source

Thrown at cmd/codegen/generator/go/templates/module_funcs.go:376

		if ok {
			stype, ok := asInlineStructAst(fnDecl.Type.Params.List[i].Type)
			if !ok {
				return nil, fmt.Errorf("expected struct type for %s", param.Name())
			}

			parent := &paramSpec{
				name:      params.At(i).Name(),
				paramType: param.Type(),
			}

			paramFields := unpackASTFields(stype.Fields)
			for f := range paramType.NumFields() {
				spec, err := ps.parseParamSpecVar(paramType.Field(f), paramFields[f], paramFields[f].Doc.Text(), paramFields[f].Comment.Text())
				if err != nil {
					return nil, err
				}
				if spec.isContext {
					return nil, fmt.Errorf("unexpected context type in inline field %s", spec.name)
				}
				spec.parent = parent
				specs = append(specs, spec)
			}
			return specs, nil
		}
	}

	// if other parameter passing schemes fail, just treat each remaining arg
	// as a top-level param
	paramFields := unpackASTFields(fnDecl.Type.Params)
	for ; i < params.Len(); i++ {
		docComment, lineComment := ps.commentForFuncField(fnDecl, paramFields, i)
		spec, err := ps.parseParamSpecVar(params.At(i), paramFields[i], docComment.Text(), lineComment.Text())
		if err != nil {
			return nil, err
		}
		if spec.isContext {

View on GitHub (pinned to 82ba2681db)

Solutions

1. Remove the context.Context field from the inline struct
2. Keep ctx as the first parameter of the function itself, not inside the struct
3. Use a different type for the field if state was intended

Example fix

// before
func (m *Mod) Foo(ctx context.Context, args struct {
  Ctx context.Context
  Name string
}) error

// after
func (m *Mod) Foo(ctx context.Context, args struct {
  Name string
}) error

// ensure no context.Context fields inside inline-struct args
for _, f := range reflect.TypeOf(args).FieldList() /* compile-time: just don't declare it */ {}

if err := runCodegen(); err != nil {
    if strings.Contains(err.Error(), "unexpected context type in inline field") {
        // remove the ctx field from the struct
    }
}

When it happens

Trigger: Declaring a context.Context field inside the anonymous struct used as a function's single argument object.

Common situations: Copy-pasting a normal function signature's parameters into a struct; misunderstanding that only the top-level function may take ctx.

Related errors

• expected struct type for %s
• could not encode default value %q: %w
• unexpected context type for arg %s
• nested structs are not supported
• defaultPath pragma %q, must be a valid string

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/f6af0f0bd59a1536. Report an issue: GitHub.