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Add editions helper functions for resolving features to protoutil (#283)
These helpers, in particular `protoutil.ResolveFeature` and `protoutil.ResolveCustomFeature`, will be used from updated checks for `buf breaking`, which will allow the tool to understand the features-related semantics of the schema. This way, it can correctly report issues with incompatible changes to features in editions source files. And it can also allow changing a file's syntax (like migrating from proto2 or proto3 to editions) as long as there are no actual semantic changes to the schema.
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| // Copyright 2020-2024 Buf Technologies, Inc. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
|
||
| package protoutil | ||
|
|
||
| import ( | ||
| "fmt" | ||
|
|
||
| "google.golang.org/protobuf/reflect/protoreflect" | ||
| "google.golang.org/protobuf/types/descriptorpb" | ||
| "google.golang.org/protobuf/types/dynamicpb" | ||
|
|
||
| "github.com/bufbuild/protocompile/internal/editions" | ||
| ) | ||
|
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| // GetFeatureDefault gets the default value for the given feature and the given | ||
| // edition. The given feature must represent a field of the google.protobuf.FeatureSet | ||
| // message and must not be an extension. | ||
| // | ||
| // If the given field is from a dynamically built descriptor (i.e. it's containing | ||
| // message descriptor is different from the linked-in descriptor for | ||
| // [*descriptorpb.FeatureSet]), the returned value may be a dynamic value. In such | ||
| // cases, the value may not be directly usable using [protoreflect.Message.Set] with | ||
| // an instance of [*descriptorpb.FeatureSet] and must instead be used with a | ||
| // [*dynamicpb.Message]. | ||
| // | ||
| // To get the default value of a custom feature, use [GetCustomFeatureDefault] | ||
| // instead. | ||
| func GetFeatureDefault(edition descriptorpb.Edition, feature protoreflect.FieldDescriptor) (protoreflect.Value, error) { | ||
| if feature.ContainingMessage().FullName() != editions.FeatureSetDescriptor.FullName() { | ||
| return protoreflect.Value{}, fmt.Errorf("feature %s is a field of %s but should be a field of %s", | ||
| feature.Name(), feature.ContainingMessage().FullName(), editions.FeatureSetDescriptor.FullName()) | ||
| } | ||
| var msgType protoreflect.MessageType | ||
| if feature.ContainingMessage() == editions.FeatureSetDescriptor { | ||
| msgType = editions.FeatureSetType | ||
| } else { | ||
| msgType = dynamicpb.NewMessageType(feature.ContainingMessage()) | ||
| } | ||
| return editions.GetFeatureDefault(edition, msgType, feature) | ||
| } | ||
|
|
||
| // GetCustomFeatureDefault gets the default value for the given custom feature | ||
| // and given edition. A custom feature is a field whose containing message is the | ||
| // type of an extension field of google.protobuf.FeatureSet. The given extension | ||
| // describes that extension field and message type. The given feature must be a | ||
| // field of that extension's message type. | ||
| func GetCustomFeatureDefault(edition descriptorpb.Edition, extension protoreflect.ExtensionType, feature protoreflect.FieldDescriptor) (protoreflect.Value, error) { | ||
| extDesc := extension.TypeDescriptor() | ||
| if extDesc.ContainingMessage().FullName() != editions.FeatureSetDescriptor.FullName() { | ||
| return protoreflect.Value{}, fmt.Errorf("extension %s does not extend %s", extDesc.FullName(), editions.FeatureSetDescriptor.FullName()) | ||
| } | ||
| if extDesc.Message() == nil { | ||
| return protoreflect.Value{}, fmt.Errorf("extensions of %s should be messages; %s is instead %s", | ||
| editions.FeatureSetDescriptor.FullName(), extDesc.FullName(), extDesc.Kind().String()) | ||
| } | ||
| if feature.IsExtension() { | ||
| return protoreflect.Value{}, fmt.Errorf("feature %s is an extension, but feature extension %s may not itself have extensions", | ||
| feature.FullName(), extDesc.FullName()) | ||
| } | ||
| if feature.ContainingMessage().FullName() != extDesc.Message().FullName() { | ||
| return protoreflect.Value{}, fmt.Errorf("feature %s is a field of %s but should be a field of %s", | ||
| feature.Name(), feature.ContainingMessage().FullName(), extDesc.Message().FullName()) | ||
| } | ||
| if feature.ContainingMessage() != extDesc.Message() { | ||
| return protoreflect.Value{}, fmt.Errorf("feature %s has a different message descriptor from the given extension type for %s", | ||
| feature.Name(), extDesc.Message().FullName()) | ||
| } | ||
| return editions.GetFeatureDefault(edition, extension.Zero().Message().Type(), feature) | ||
| } | ||
|
|
||
| // ResolveFeature resolves a feature for the given descriptor. | ||
| // | ||
| // If the given element is in a proto2 or proto3 syntax file, this skips | ||
| // resolution and just returns the relevant default (since such files are not | ||
| // allowed to override features). If neither the given element nor any of its | ||
| // ancestors override the given feature, the relevant default is returned. | ||
| // | ||
| // This has the same caveat as GetFeatureDefault if the given feature is from a | ||
| // dynamically built descriptor. | ||
| func ResolveFeature(element protoreflect.Descriptor, feature protoreflect.FieldDescriptor) (protoreflect.Value, error) { | ||
| edition := editions.GetEdition(element) | ||
| defaultVal, err := GetFeatureDefault(edition, feature) | ||
| if err != nil { | ||
| return protoreflect.Value{}, err | ||
| } | ||
| return resolveFeature(edition, defaultVal, element, feature) | ||
| } | ||
|
|
||
| // ResolveCustomFeature resolves a custom feature for the given extension and | ||
| // field descriptor. | ||
| // | ||
| // The given extension must be an extension of google.protobuf.FeatureSet that | ||
| // represents a non-repeated message value. The given feature is a field in | ||
| // that extension's message type. | ||
| // | ||
| // If the given element is in a proto2 or proto3 syntax file, this skips | ||
| // resolution and just returns the relevant default (since such files are not | ||
| // allowed to override features). If neither the given element nor any of its | ||
| // ancestors override the given feature, the relevant default is returned. | ||
| func ResolveCustomFeature(element protoreflect.Descriptor, extension protoreflect.ExtensionType, feature protoreflect.FieldDescriptor) (protoreflect.Value, error) { | ||
| edition := editions.GetEdition(element) | ||
| defaultVal, err := GetCustomFeatureDefault(edition, extension, feature) | ||
| if err != nil { | ||
| return protoreflect.Value{}, err | ||
| } | ||
| return resolveFeature(edition, defaultVal, element, extension.TypeDescriptor(), feature) | ||
| } | ||
|
|
||
| func resolveFeature( | ||
| edition descriptorpb.Edition, | ||
| defaultVal protoreflect.Value, | ||
| element protoreflect.Descriptor, | ||
| fields ...protoreflect.FieldDescriptor, | ||
| ) (protoreflect.Value, error) { | ||
| if edition == descriptorpb.Edition_EDITION_PROTO2 || edition == descriptorpb.Edition_EDITION_PROTO3 { | ||
| // these syntax levels can't specify features, so we can short-circuit the search | ||
| // through the descriptor hierarchy for feature overrides | ||
| return defaultVal, nil | ||
| } | ||
| val, err := editions.ResolveFeature(element, fields...) | ||
| if err != nil { | ||
| return protoreflect.Value{}, err | ||
| } | ||
| if val.IsValid() { | ||
| return val, nil | ||
| } | ||
| return defaultVal, nil | ||
| } |
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