Validate struct builder sufficiency

errors.go

@@ -2,6 +2,7 @@ package ipld
 
 import (
 	"fmt"
+	"strings"
 )
 
 // ErrWrongKind may be returned from functions on the Node interface when
@@ -152,6 +153,15 @@ func (e ErrIteratorOverread) Error() string {
 
 type ErrCannotBeNull struct{} // Review: arguably either ErrInvalidKindForNodePrototype.
 
-type ErrMissingRequiredField struct{}     // only possible for typed nodes -- specifically, struct types.
+// ErrMissingRequiredField is returned when calling 'Finish' on a NodeAssembler
+// for a Struct that has not has all required fields set.
+type ErrMissingRequiredField struct {
+	Missing []string
+}
+
+func (e ErrMissingRequiredField) Error() string {
+	return "missing required fields: " + strings.Join(e.Missing, ",")
+}
+
 type ErrListOverrun struct{}              // only possible for typed nodes -- specifically, struct types with list (aka tuple) representations.
 type ErrInvalidUnionDiscriminant struct{} // only possible for typed nodes -- specifically, union types.

schema/gen/go/genStruct.go

@@ -507,7 +507,17 @@ func (g structBuilderGenerator) emitMapAssemblerMethods(w io.Writer) {
 			case maState_finished:
 				panic("invalid state: Finish cannot be called on an assembler that's already finished")
 			}
-			//FIXME check if all required fields are set
+			if ma.s & fieldBits__{{ $type | TypeSymbol }}_sufficient != fieldBits__{{ $type | TypeSymbol }}_sufficient {
+				err := ipld.ErrMissingRequiredField{Missing: make([]string, 0)}
+				{{- range $i, $field := .Type.Fields }}
+				{{- if not $field.IsMaybe}}
+				if ma.s & fieldBit__{{ $type | TypeSymbol }}_{{ $field | FieldSymbolUpper }} == 0 {
+					err.Missing = append(err.Missing, "{{ $field.Name }}")
+				}
+				{{- end}}
+				{{- end}}
+				return err
+			}
 			ma.state = maState_finished
 			*ma.m = schema.Maybe_Value
 			return nil

schema/gen/go/testStructsContainingMaybe_test.go

@@ -171,4 +171,27 @@ func TestStructsContainingMaybe(t *testing.T) {
 			}
 		})
 	})
+
+	genAndCompileAndTest(t, "stroct3", "main", ts, adjCfg, func(t *testing.T, getPrototypeByName func(string) ipld.NodePrototype) {
+		t.Run("insufficient", func(t *testing.T) {
+			nrp := getPrototypeByName("Stroct")
+			t.Run("typed-create", func(t *testing.T) {
+				b := nrp.NewBuilder()
+				mb, err := b.BeginMap(0)
+				if err != nil {
+					t.Fatal(err)
+				}
+				v, err := mb.AssembleEntry("f1")
+				if err != nil {
+					t.Fatal(err)
+				}
+				v.AssignString("v1")
+
+				err = mb.Finish()
+				if _, ok := err.(ipld.ErrMissingRequiredField); !ok {
+					t.Fatalf("Expected error for missing field, got %v", err)
+				}
+			})
+		})
+	})
 }