feat: add inline union representation to schema parser

Closes: ipld/ipld#286

schema/dmt/compile.go

@@ -334,11 +334,15 @@ func spawnType(ts *schema.TypeSystem, name schema.TypeName, defn TypeDefn) (sche
 				switch {
 				case member.TypeName != nil:
 					memberName := *member.TypeName
-					validMember(memberName)
+					if err := validMember(memberName); err != nil {
+						return nil, err
+					}
 					table[kind] = memberName
 				case member.UnionMemberInlineDefn != nil:
 					tname := anonLinkName(*member.UnionMemberInlineDefn.TypeDefnLink)
-					validMember(tname)
+					if err := validMember(tname); err != nil {
+						return nil, err
+					}
 					table[kind] = tname
 				}
 			}
@@ -351,21 +355,41 @@ func spawnType(ts *schema.TypeSystem, name schema.TypeName, defn TypeDefn) (sche
 				switch {
 				case member.TypeName != nil:
 					memberName := *member.TypeName
-					validMember(memberName)
+					if err := validMember(memberName); err != nil {
+						return nil, err
+					}
 					table[key] = memberName
 				case member.UnionMemberInlineDefn != nil:
 					tname := anonLinkName(*member.UnionMemberInlineDefn.TypeDefnLink)
-					validMember(tname)
+					if err := validMember(tname); err != nil {
+						return nil, err
+					}
 					table[key] = tname
 				}
 			}
 			repr = schema.SpawnUnionRepresentationKeyed(table)
 		case typ.Representation.UnionRepresentation_StringPrefix != nil:
 			prefixes := typ.Representation.UnionRepresentation_StringPrefix.Prefixes
 			for _, key := range prefixes.Keys {
-				validMember(prefixes.Values[key])
+				if err := validMember(prefixes.Values[key]); err != nil {
+					return nil, err
+				}
 			}
 			repr = schema.SpawnUnionRepresentationStringprefix("", prefixes.Values)
+		case typ.Representation.UnionRepresentation_Inline != nil:
+			rp := typ.Representation.UnionRepresentation_Inline
+			if rp.DiscriminantKey == "" {
+				return nil, fmt.Errorf("inline union has empty discriminantKey value")
+			}
+			if rp.DiscriminantTable.Keys == nil || rp.DiscriminantTable.Values == nil {
+				return nil, fmt.Errorf("inline union has empty discriminantTable")
+			}
+			for _, key := range rp.DiscriminantTable.Keys {
+				if err := validMember(rp.DiscriminantTable.Values[key]); err != nil {
+					return nil, err
+				}
+			}
+			repr = schema.SpawnUnionRepresentationInline(rp.DiscriminantKey, rp.DiscriminantTable.Values)
 		default:
 			return nil, fmt.Errorf("TODO: support other union repr in schema package")
 		}

schema/dsl/parse.go

@@ -645,6 +645,31 @@ func (p *parser) typeUnion() (*dmt.TypeDefnUnion, error) {
 			repr.Prefixes.Values[key] = *defn.Members[i].TypeName
 		}
 		defn.Representation.UnionRepresentation_StringPrefix = repr
+	case "inline":
+		optMap, err := p.consumeStringMap()
+		if err != nil {
+			return nil, err
+		}
+		discriminantKey, hasDiscriminantKey := optMap["discriminantKey"]
+		if !hasDiscriminantKey {
+			return nil, p.errf("no discriminantKey value provided for inline repr")
+		}
+		repr := &dmt.UnionRepresentation_Inline{
+			DiscriminantKey: discriminantKey,
+			DiscriminantTable: dmt.Map__String__TypeName{
+				Values: map[string]string{},
+			},
+		}
+		// TODO: verify member types all have map representation
+		for i, qkey := range reprKeys {
+			key, err := strconv.Unquote(qkey)
+			if err != nil {
+				return nil, fmt.Errorf("invalid discriminant key %q: %w", key, err)
+			}
+			repr.DiscriminantTable.Keys = append(repr.DiscriminantTable.Keys, key)
+			repr.DiscriminantTable.Values[key] = *defn.Members[i].TypeName
+		}
+		defn.Representation.UnionRepresentation_Inline = repr
 	default:
 		return nil, p.errf("TODO: union repr %q", reprName)
 	}

schema/tmpBuilders.go

@@ -141,6 +141,9 @@ func SpawnUnionRepresentationKinded(table map[datamodel.Kind]TypeName) UnionRepr
 func SpawnUnionRepresentationStringprefix(delim string, table map[string]TypeName) UnionRepresentation_Stringprefix {
 	return UnionRepresentation_Stringprefix{delim, table}
 }
+func SpawnUnionRepresentationInline(discriminantKey string, table map[string]TypeName) UnionRepresentation_Inline {
+	return UnionRepresentation_Inline{discriminantKey, table}
+}
 
 func SpawnEnum(name TypeName, members []string, repr EnumRepresentation) *TypeEnum {
 	return &TypeEnum{typeBase{name, nil}, members, repr}