Reject unversioned party documents

internal/config/party.go

@@ -83,17 +83,12 @@ type PartyClass struct {
 	Level *int
 }
 
-// ParseParty classifies and, when selected by schema_version, strictly parses
-// a party source. An unversioned source takes the deliberately opaque legacy
-// compatibility path; see party_legacy.go.
+// ParseParty strictly parses one supported party document.
 func ParseParty(data []byte) (*PartyDocument, error) {
 	root, decoder, err := parsePartyFirstDocument(data)
 	if err != nil {
 		return nil, err
 	}
-	if !partyDocumentSelectsCanonical(root) {
-		return classifyLegacyPartyDocument(), nil
-	}
 	if err := requireNoTrailingPartyDocuments(decoder); err != nil {
 		return nil, err
 	}
@@ -119,25 +114,12 @@ func parsePartyFirstDocument(data []byte) (*yaml.Node, *yaml.Decoder, error) {
 	return document.Content[0], decoder, nil
 }
 
-func partyDocumentSelectsCanonical(root *yaml.Node) bool {
-	if root == nil || root.Kind != yaml.MappingNode {
-		return false
-	}
-	for index := 0; index+1 < len(root.Content); index += 2 {
-		key := root.Content[index]
-		if key.Kind == yaml.ScalarNode && key.Tag == "!!str" && key.Value == "schema_version" {
-			return true
-		}
-	}
-	return false
-}
-
 func requireNoTrailingPartyDocuments(decoder *yaml.Decoder) error {
 	var trailing yaml.Node
 	if err := decoder.Decode(&trailing); err == nil {
-		return fmt.Errorf("canonical party must contain exactly one YAML document")
+		return fmt.Errorf("party must contain exactly one YAML document")
 	} else if err != io.EOF {
-		return fmt.Errorf("decode trailing canonical party YAML: %w", err)
+		return fmt.Errorf("decode trailing party YAML: %w", err)
 	}
 	return nil
 }
@@ -147,17 +129,21 @@ func parseCanonicalParty(root *yaml.Node, raw []byte) (*CanonicalParty, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	version, ok := fields["schema_version"]
+	if !ok {
+		return nil, fmt.Errorf("party.schema_version is required; supported schema_version is %q", PartySchemaVersion)
+	}
+	schemaVersion, err := partyRequiredString(map[string]*yaml.Node{"schema_version": version}, "schema_version", "party")
+	if err != nil {
+		return nil, fmt.Errorf("party.schema_version must be a non-empty string; supported schema_version is %q", PartySchemaVersion)
+	}
+	if schemaVersion != PartySchemaVersion {
+		return nil, fmt.Errorf("party.schema_version %q is unsupported; supported schema_version is %q", schemaVersion, PartySchemaVersion)
+	}
 	if err := partyKnownFields(fields, "party", "schema_version", "characters"); err != nil {
 		return nil, err
 	}
-
-	version, err := partyRequiredString(fields, "schema_version", "party")
-	if err != nil {
-		return nil, err
-	}
-	if version != PartySchemaVersion {
-		return nil, fmt.Errorf("party.schema_version %q is unsupported", version)
-	}
 	charactersNode, ok := fields["characters"]
 	if !ok {
 		return nil, fmt.Errorf("party.characters is required")