Separate schema field discovery and assembly

internal/engine/schema_fields.go

@@ -0,0 +1,102 @@
+package engine
+
+import "reflect"
+
+func (b *schemaBuilder) describeOrdinaryField(owner *typeDescriptor, field reflect.StructField, index int, name string, secret bool, path Path) *schemaIssue {
+	fieldPath := path.Key(name)
+	fieldType, issue := b.describe(field.Type, fieldPath)
+	if issue != nil {
+		return issue
+	}
+	if issue := addField(owner, fieldDescriptor{name: name, index: []int{index}, descriptor: fieldType, secret: secret}, path); issue != nil {
+		return issue
+	}
+	owner.members = append(owner.members, structMember{index: index, name: name, descriptor: fieldType})
+	return nil
+}
+
+func (b *schemaBuilder) describeInlineField(owner *typeDescriptor, field reflect.StructField, index int, secret bool, path Path) *schemaIssue {
+	inlineType, issue := inlineFieldType(field.Type, path)
+	if issue != nil {
+		return issue
+	}
+	if inlineType.Kind() == reflect.Map && field.Type.Kind() == reflect.Pointer {
+		return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "inline maps cannot be pointers"}
+	}
+
+	switch inlineType.Kind() {
+	case reflect.Struct:
+		return b.describeInlineStruct(owner, field, inlineType, index, secret, path)
+	case reflect.Map:
+		return b.describeInlineMap(owner, inlineType, index, secret, path)
+	default:
+		return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "inline field must be a struct, pointer to struct, or string-keyed map"}
+	}
+}
+
+func inlineFieldType(fieldType reflect.Type, path Path) (reflect.Type, *schemaIssue) {
+	current := fieldType
+	seenPointers := make(map[reflect.Type]bool)
+	for current.Kind() == reflect.Pointer {
+		if seenPointers[current] {
+			return nil, &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "inline pointer chain must terminate in a struct"}
+		}
+		seenPointers[current] = true
+		current = current.Elem()
+	}
+	return current, nil
+}
+
+func (b *schemaBuilder) describeInlineStruct(owner *typeDescriptor, field reflect.StructField, inlineType reflect.Type, index int, secret bool, path Path) *schemaIssue {
+	if b.building[inlineType] {
+		return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "recursive inline struct is not supported"}
+	}
+	child, issue := b.describe(inlineType, path)
+	if issue != nil {
+		return issue
+	}
+	if child.kind != descriptorStruct {
+		return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "inline field must be a structural struct or string-keyed map"}
+	}
+	for _, nested := range child.fields {
+		nested.index = prependIndex(index, nested.index)
+		nested.secret = secret || nested.secret
+		if issue := addField(owner, nested, path); issue != nil {
+			return issue
+		}
+	}
+	if child.inlineMap != nil {
+		nested := *child.inlineMap
+		nested.index = prependIndex(index, nested.index)
+		nested.secret = secret || nested.secret
+		if owner.inlineMap != nil {
+			return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "configuration object has more than one inline map"}
+		}
+		owner.inlineMap = &nested
+	}
+
+	memberType, issue := b.describe(field.Type, path)
+	if issue != nil {
+		return issue
+	}
+	owner.members = append(owner.members, structMember{index: index, descriptor: memberType, inline: true})
+	return nil
+}
+
+func (b *schemaBuilder) describeInlineMap(owner *typeDescriptor, inlineType reflect.Type, index int, secret bool, path Path) *schemaIssue {
+	if inlineType.Key().Kind() != reflect.String {
+		return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "inline map must have string keys"}
+	}
+	if owner.inlineMap != nil {
+		return &schemaIssue{code: CodeSchemaInline, path: path.clone(), message: "configuration object has more than one inline map"}
+	}
+
+	fieldPath := path.Key("*")
+	fieldType, issue := b.describe(inlineType, fieldPath)
+	if issue != nil {
+		return issue
+	}
+	owner.inlineMap = &fieldDescriptor{index: []int{index}, descriptor: fieldType, secret: secret, inlineMap: true}
+	owner.members = append(owner.members, structMember{index: index, descriptor: fieldType, inline: true})
+	return nil
+}