src/tools/proto_merger/proto_merger.cc - third_party/perfetto - Git at Google

 /*
  * Copyright (C) 2021 The Android Open Source Project
  *
  * 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.
  */

 #include "src/tools/proto_merger/proto_merger.h"

 #include <optional>

 #include "perfetto/base/logging.h"
 #include "perfetto/base/status.h"
 #include "perfetto/ext/base/string_utils.h"

 namespace perfetto {
 namespace proto_merger {
 namespace {

 template <typename Key, typename Value>
 std::optional<Value> FindInMap(const std::map<Key, Value>& map,
                                const Key& key) {
   auto it = map.find(key);
   return it == map.end() ? std::nullopt : std::make_optional(it->second);
 }

 // Finds the given 'name' in the vector by comparing against
 // the field named 'name' for each item in the vector.
 // T is ProtoFile::Enum, ProtoFile::Oneof or ProtoFile::Message.
 template <typename T>
 const T* FindByName(const std::vector<T>& items, const std::string& name) {
   for (const auto& item : items) {
     if (item.name == name)
       return &item;
   }
   return nullptr;
 }

 // Compute the items present in the |input| vector but deleted in
 // the |upstream| vector by looking at the field |name|.
 // T is ProtoFile::Enum, ProtoFile::Oneof or ProtoFile::Message.
 template <typename T>
 std::vector<T> ComputeDeletedByName(const std::vector<T>& input,
                                     const std::vector<T>& upstream) {
   std::vector<T> deleted;
   std::set<std::string> seen;
   for (const auto& upstream_item : upstream) {
     auto* input_item = FindByName(input, upstream_item.name);
     if (!input_item)
       continue;
     seen.insert(input_item->name);
   }

   for (const auto& input_item : input) {
     if (seen.count(input_item.name))
       continue;
     deleted.emplace_back(input_item);
   }
   return deleted;
 }

 // Finds the given 'number' in the vector by comparing against
 // the field named 'number for each item in the vector.
 // T is ProtoFile::EnumValue or ProtoFile::Field.
 template <typename T>
 const T* FindByNumber(const std::vector<T>& items, int number) {
   for (const auto& item : items) {
     if (item.number == number)
       return &item;
   }
   return nullptr;
 }

 // Compute the items present in the |input| vector but deleted in
 // the |upstream| vector by looking at the field |number|.
 // T is ProtoFile::EnumValue or ProtoFile::Field.
 template <typename T>
 std::vector<T> ComputeDeletedByNumber(const std::vector<T>& input,
                                       const std::vector<T>& upstream) {
   std::vector<T> deleted;
   std::set<int> seen;
   for (const auto& upstream_item : upstream) {
     auto* input_item = FindByNumber(input, upstream_item.number);
     if (!input_item)
       continue;
     seen.insert(input_item->number);
   }

   for (const auto& input_item : input) {
     if (seen.count(input_item.number))
       continue;
     deleted.emplace_back(input_item);
   }
   return deleted;
 }

 ProtoFile::Enum::Value MergeEnumValue(const ProtoFile::Enum::Value& input,
                                       const ProtoFile::Enum::Value& upstream) {
   PERFETTO_CHECK(input.number == upstream.number);

   ProtoFile::Enum::Value out;
   out.name = upstream.name;

   // Get the comments from the source of truth.
   out.leading_comments = upstream.leading_comments;
   out.trailing_comments = upstream.trailing_comments;

   // Get everything else from the input.
   out.number = input.number;
   out.options = input.options;
   return out;
 }

 ProtoFile::Enum MergeEnum(const ProtoFile::Enum& input,
                           const ProtoFile::Enum& upstream) {
   PERFETTO_CHECK(input.name == upstream.name);

   ProtoFile::Enum out;
   out.name = upstream.name;

   // Get the comments from the source of truth.
   out.leading_comments = upstream.leading_comments;
   out.trailing_comments = upstream.trailing_comments;

   for (const auto& upstream_value : upstream.values) {
     // If an enum is allowlisted, we implicitly assume that all its
     // values are also allowed. Therefore, if the value doesn't exist
     // in the input, just take it from the source of truth.
     auto* input_value = FindByNumber(input.values, upstream_value.number);
     auto out_value = input_value ? MergeEnumValue(*input_value, upstream_value)
                                  : upstream_value;
     out.values.emplace_back(std::move(out_value));
   }

   // Compute all the values present in the input but deleted in the
   // source of truth.
   out.deleted_values = ComputeDeletedByNumber(input.values, upstream.values);
   return out;
 }

 std::vector<ProtoFile::Enum> MergeEnums(
     const std::vector<ProtoFile::Enum>& input,
     const std::vector<ProtoFile::Enum>& upstream,
     const std::set<std::string>& allowlist) {
   std::vector<ProtoFile::Enum> out;
   for (const auto& upstream_enum : upstream) {
     auto* input_enum = FindByName(input, upstream_enum.name);
     if (!input_enum) {
       // If the enum is missing from the input but is present
       // in the allowlist, take the whole enum from the
       // source of truth.
       if (allowlist.count(upstream_enum.name))
         out.emplace_back(upstream_enum);
       continue;
     }

     // Otherwise, merge the enums from the input and source of truth.
     out.emplace_back(MergeEnum(*input_enum, upstream_enum));
   }
   return out;
 }

 base::Status MergeField(const ProtoFile::Field& input,
                         const ProtoFile::Field& upstream,
                         ProtoFile::Field& out) {
   PERFETTO_CHECK(input.number == upstream.number);

   if (input.packageless_type != upstream.packageless_type) {
     return base::ErrStatus(
         "The type of field with id %d and name %s (source of truth name: %s) "
         "changed from %s to %s. Please resolve conflict manually before "
         "rerunning.",
         input.number, input.name.c_str(), upstream.name.c_str(),
         input.packageless_type.c_str(), upstream.packageless_type.c_str());
   }

   // If the packageless type name is the same but the type is different
   // mostly we should error however sometimes it is useful to allow downstream
   // to 'alias' an upstream type. For example 'Foo' to an existing internal
   // type in another package 'my.private.Foo'.
   if (input.type != upstream.type) {
     if (!base::EndsWith(upstream.type, "Atom")) {
       return base::ErrStatus(
           "Upstream field with id %d and name '%s' "
           "(source of truth name: '%s') uses the type '%s' but we have the "
           "existing downstream type '%s'. Resolve this manually either by "
           "allowing this explicitly in proto_merger or editing the proto.",
           input.number, input.name.c_str(), upstream.name.c_str(),
           upstream.type.c_str(), input.type.c_str());
     }
   }

   // Get the comments, label and the name from the source of truth.
   out.leading_comments = upstream.leading_comments;
   out.trailing_comments = upstream.trailing_comments;
   out.label = upstream.label;
   out.name = upstream.name;

   // Get everything else from the input.
   out.number = input.number;
   out.options = input.options;
   out.packageless_type = input.packageless_type;
   out.type = input.type;

   return base::OkStatus();
 }

 base::Status MergeFields(const std::vector<ProtoFile::Field>& input,
                          const std::vector<ProtoFile::Field>& upstream,
                          const std::set<int>& allowlist,
                          std::vector<ProtoFile::Field>& out) {
   for (const auto& upstream_field : upstream) {
     auto* input_field = FindByNumber(input, upstream_field.number);
     if (!input_field) {
       // If the field is missing from the input but is present
       // in the allowlist, take the whole field from the
       // source of truth.
       if (allowlist.count(upstream_field.number))
         out.emplace_back(upstream_field);
       continue;
     }

     // Otherwise, merge the fields from the input and source of truth.
     ProtoFile::Field out_field;
     base::Status status = MergeField(*input_field, upstream_field, out_field);
     if (!status.ok())
       return status;
     out.emplace_back(std::move(out_field));
   }
   return base::OkStatus();
 }

 // We call both of these just "Merge" so that |MergeRecursive| below can
 // reference them with the same name.
 base::Status Merge(const ProtoFile::Oneof& input,
                    const ProtoFile::Oneof& upstream,
                    const Allowlist::Oneof& allowlist,
                    ProtoFile::Oneof& out);

 base::Status Merge(const ProtoFile::Message& input,
                    const ProtoFile::Message& upstream,
                    const Allowlist::Message& allowlist,
                    ProtoFile::Message& out);

 template <typename T, typename AllowlistType>
 base::Status MergeRecursive(
     const std::vector<T>& input,
     const std::vector<T>& upstream,
     const std::map<std::string, AllowlistType>& allowlist_map,
     std::vector<T>& out) {
   for (const auto& upstream_item : upstream) {
     auto opt_allowlist = FindInMap(allowlist_map, upstream_item.name);
     auto* input_item = FindByName(input, upstream_item.name);

     // If the value is not present in the input and the allowlist doesn't
     // exist either, this field is not approved so should not be included
     // in the output.
     if (!input_item && !opt_allowlist)
       continue;

     // If the input value doesn't exist, create a fake "input" that we can pass
     // to the merge function. This basically has the effect that the upstream
     // item is taken but *not* recursively; i.e. any fields which are inside the
     // message/oneof are checked against the allowlist individually. If we just
     // took the whole upstream here, we could add fields which were not
     // allowlisted.
     T input_or_fake;
     if (input_item) {
       input_or_fake = *input_item;
     } else {
       input_or_fake.name = upstream_item.name;
     }

     auto allowlist = opt_allowlist.value_or(AllowlistType{});
     T out_item;
     auto status = Merge(input_or_fake, upstream_item, allowlist, out_item);
     if (!status.ok())
       return status;
     out.emplace_back(std::move(out_item));
   }
   return base::OkStatus();
 }

 base::Status Merge(const ProtoFile::Oneof& input,
                    const ProtoFile::Oneof& upstream,
                    const Allowlist::Oneof& allowlist,
                    ProtoFile::Oneof& out) {
   PERFETTO_CHECK(input.name == upstream.name);
   out.name = input.name;

   // Get the comments from the source of truth.
   out.leading_comments = upstream.leading_comments;
   out.trailing_comments = upstream.trailing_comments;

   // Compute all the fields present in the input but deleted in the
   // source of truth.
   out.deleted_fields = ComputeDeletedByNumber(input.fields, upstream.fields);

   // Finish by merging the list of fields.
   return MergeFields(input.fields, upstream.fields, allowlist, out.fields);
 }

 base::Status Merge(const ProtoFile::Message& input,
                    const ProtoFile::Message& upstream,
                    const Allowlist::Message& allowlist,
                    ProtoFile::Message& out) {
   PERFETTO_CHECK(input.name == upstream.name);
   out.name = input.name;

   // Get the comments from the source of truth.
   out.leading_comments = upstream.leading_comments;
   out.trailing_comments = upstream.trailing_comments;

   // Compute all the values present in the input but deleted in the
   // source of truth.
   out.deleted_enums = ComputeDeletedByName(input.enums, upstream.enums);
   out.deleted_nested_messages =
       ComputeDeletedByName(input.nested_messages, upstream.nested_messages);
   out.deleted_oneofs = ComputeDeletedByName(input.oneofs, upstream.oneofs);
   out.deleted_fields = ComputeDeletedByNumber(input.fields, upstream.fields);

   // Merge any nested enum types.
   out.enums = MergeEnums(input.enums, upstream.enums, allowlist.enums);

   // Merge any nested message types.
   auto status = MergeRecursive(input.nested_messages, upstream.nested_messages,
                                allowlist.nested_messages, out.nested_messages);
   if (!status.ok())
     return status;

   // Merge any oneofs.
   status = MergeRecursive(input.oneofs, upstream.oneofs, allowlist.oneofs,
                           out.oneofs);
   if (!status.ok())
     return status;

   // Finish by merging the list of fields.
   return MergeFields(input.fields, upstream.fields, allowlist.fields,
                      out.fields);
 }

 }  // namespace

 base::Status MergeProtoFiles(const ProtoFile& input,
                              const ProtoFile& upstream,
                              const Allowlist& allowlist,
                              ProtoFile& out) {
   // The preamble is taken directly from upstream. This allows private stuff
   // to be in the preamble without being present in upstream.
   out.preamble = input.preamble;

   // Compute all the enums and messages present in the input but deleted in the
   // source of truth.
   out.deleted_enums = ComputeDeletedByName(input.enums, upstream.enums);
   out.deleted_messages =
       ComputeDeletedByName(input.messages, upstream.messages);

   // Merge the top-level enums.
   out.enums = MergeEnums(input.enums, upstream.enums, allowlist.enums);

   // Finish by merging the top-level messages.
   return MergeRecursive(input.messages, upstream.messages, allowlist.messages,
                         out.messages);
 }

 }  // namespace proto_merger
 }  // namespace perfetto
	/*
	* Copyright (C) 2021 The Android Open Source Project
	*
	* 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.
	*/

	#include "src/tools/proto_merger/proto_merger.h"

	#include <optional>

	#include "perfetto/base/logging.h"
	#include "perfetto/base/status.h"
	#include "perfetto/ext/base/string_utils.h"

	namespace perfetto {
	namespace proto_merger {
	namespace {

	template <typename Key, typename Value>
	std::optional<Value> FindInMap(const std::map<Key, Value>& map,
	const Key& key) {
	auto it = map.find(key);
	return it == map.end() ? std::nullopt : std::make_optional(it->second);
	}

	// Finds the given 'name' in the vector by comparing against
	// the field named 'name' for each item in the vector.
	// T is ProtoFile::Enum, ProtoFile::Oneof or ProtoFile::Message.
	template <typename T>
	const T* FindByName(const std::vector<T>& items, const std::string& name) {
	for (const auto& item : items) {
	if (item.name == name)
	return &item;
	}
	return nullptr;
	}

	// Compute the items present in the \|input\| vector but deleted in
	// the \|upstream\| vector by looking at the field \|name\|.
	// T is ProtoFile::Enum, ProtoFile::Oneof or ProtoFile::Message.
	template <typename T>
	std::vector<T> ComputeDeletedByName(const std::vector<T>& input,
	const std::vector<T>& upstream) {
	std::vector<T> deleted;
	std::set<std::string> seen;
	for (const auto& upstream_item : upstream) {
	auto* input_item = FindByName(input, upstream_item.name);
	if (!input_item)
	continue;
	seen.insert(input_item->name);
	}

	for (const auto& input_item : input) {
	if (seen.count(input_item.name))
	continue;
	deleted.emplace_back(input_item);
	}
	return deleted;
	}

	// Finds the given 'number' in the vector by comparing against
	// the field named 'number for each item in the vector.
	// T is ProtoFile::EnumValue or ProtoFile::Field.
	template <typename T>
	const T* FindByNumber(const std::vector<T>& items, int number) {
	for (const auto& item : items) {
	if (item.number == number)
	return &item;
	}
	return nullptr;
	}

	// Compute the items present in the \|input\| vector but deleted in
	// the \|upstream\| vector by looking at the field \|number\|.
	// T is ProtoFile::EnumValue or ProtoFile::Field.
	template <typename T>
	std::vector<T> ComputeDeletedByNumber(const std::vector<T>& input,
	const std::vector<T>& upstream) {
	std::vector<T> deleted;
	std::set<int> seen;
	for (const auto& upstream_item : upstream) {
	auto* input_item = FindByNumber(input, upstream_item.number);
	if (!input_item)
	continue;
	seen.insert(input_item->number);
	}

	for (const auto& input_item : input) {
	if (seen.count(input_item.number))
	continue;
	deleted.emplace_back(input_item);
	}
	return deleted;
	}

	ProtoFile::Enum::Value MergeEnumValue(const ProtoFile::Enum::Value& input,
	const ProtoFile::Enum::Value& upstream) {
	PERFETTO_CHECK(input.number == upstream.number);

	ProtoFile::Enum::Value out;
	out.name = upstream.name;

	// Get the comments from the source of truth.
	out.leading_comments = upstream.leading_comments;
	out.trailing_comments = upstream.trailing_comments;

	// Get everything else from the input.
	out.number = input.number;
	out.options = input.options;
	return out;
	}

	ProtoFile::Enum MergeEnum(const ProtoFile::Enum& input,
	const ProtoFile::Enum& upstream) {
	PERFETTO_CHECK(input.name == upstream.name);

	ProtoFile::Enum out;
	out.name = upstream.name;

	// Get the comments from the source of truth.
	out.leading_comments = upstream.leading_comments;
	out.trailing_comments = upstream.trailing_comments;

	for (const auto& upstream_value : upstream.values) {
	// If an enum is allowlisted, we implicitly assume that all its
	// values are also allowed. Therefore, if the value doesn't exist
	// in the input, just take it from the source of truth.
	auto* input_value = FindByNumber(input.values, upstream_value.number);
	auto out_value = input_value ? MergeEnumValue(*input_value, upstream_value)
	: upstream_value;
	out.values.emplace_back(std::move(out_value));
	}

	// Compute all the values present in the input but deleted in the
	// source of truth.
	out.deleted_values = ComputeDeletedByNumber(input.values, upstream.values);
	return out;
	}

	std::vector<ProtoFile::Enum> MergeEnums(
	const std::vector<ProtoFile::Enum>& input,
	const std::vector<ProtoFile::Enum>& upstream,
	const std::set<std::string>& allowlist) {
	std::vector<ProtoFile::Enum> out;
	for (const auto& upstream_enum : upstream) {
	auto* input_enum = FindByName(input, upstream_enum.name);
	if (!input_enum) {
	// If the enum is missing from the input but is present
	// in the allowlist, take the whole enum from the
	// source of truth.
	if (allowlist.count(upstream_enum.name))
	out.emplace_back(upstream_enum);
	continue;
	}

	// Otherwise, merge the enums from the input and source of truth.
	out.emplace_back(MergeEnum(*input_enum, upstream_enum));
	}
	return out;
	}

	base::Status MergeField(const ProtoFile::Field& input,
	const ProtoFile::Field& upstream,
	ProtoFile::Field& out) {
	PERFETTO_CHECK(input.number == upstream.number);

	if (input.packageless_type != upstream.packageless_type) {
	return base::ErrStatus(
	"The type of field with id %d and name %s (source of truth name: %s) "
	"changed from %s to %s. Please resolve conflict manually before "
	"rerunning.",
	input.number, input.name.c_str(), upstream.name.c_str(),
	input.packageless_type.c_str(), upstream.packageless_type.c_str());
	}

	// If the packageless type name is the same but the type is different
	// mostly we should error however sometimes it is useful to allow downstream
	// to 'alias' an upstream type. For example 'Foo' to an existing internal
	// type in another package 'my.private.Foo'.
	if (input.type != upstream.type) {
	if (!base::EndsWith(upstream.type, "Atom")) {
	return base::ErrStatus(
	"Upstream field with id %d and name '%s' "
	"(source of truth name: '%s') uses the type '%s' but we have the "
	"existing downstream type '%s'. Resolve this manually either by "
	"allowing this explicitly in proto_merger or editing the proto.",
	input.number, input.name.c_str(), upstream.name.c_str(),
	upstream.type.c_str(), input.type.c_str());
	}
	}

	// Get the comments, label and the name from the source of truth.
	out.leading_comments = upstream.leading_comments;
	out.trailing_comments = upstream.trailing_comments;
	out.label = upstream.label;
	out.name = upstream.name;

	// Get everything else from the input.
	out.number = input.number;
	out.options = input.options;
	out.packageless_type = input.packageless_type;
	out.type = input.type;

	return base::OkStatus();
	}

	base::Status MergeFields(const std::vector<ProtoFile::Field>& input,
	const std::vector<ProtoFile::Field>& upstream,
	const std::set<int>& allowlist,
	std::vector<ProtoFile::Field>& out) {
	for (const auto& upstream_field : upstream) {
	auto* input_field = FindByNumber(input, upstream_field.number);
	if (!input_field) {
	// If the field is missing from the input but is present
	// in the allowlist, take the whole field from the
	// source of truth.
	if (allowlist.count(upstream_field.number))
	out.emplace_back(upstream_field);
	continue;
	}

	// Otherwise, merge the fields from the input and source of truth.
	ProtoFile::Field out_field;
	base::Status status = MergeField(*input_field, upstream_field, out_field);
	if (!status.ok())
	return status;
	out.emplace_back(std::move(out_field));
	}
	return base::OkStatus();
	}

	// We call both of these just "Merge" so that \|MergeRecursive\| below can
	// reference them with the same name.
	base::Status Merge(const ProtoFile::Oneof& input,
	const ProtoFile::Oneof& upstream,
	const Allowlist::Oneof& allowlist,
	ProtoFile::Oneof& out);

	base::Status Merge(const ProtoFile::Message& input,
	const ProtoFile::Message& upstream,
	const Allowlist::Message& allowlist,
	ProtoFile::Message& out);

	template <typename T, typename AllowlistType>
	base::Status MergeRecursive(
	const std::vector<T>& input,
	const std::vector<T>& upstream,
	const std::map<std::string, AllowlistType>& allowlist_map,
	std::vector<T>& out) {
	for (const auto& upstream_item : upstream) {
	auto opt_allowlist = FindInMap(allowlist_map, upstream_item.name);
	auto* input_item = FindByName(input, upstream_item.name);

	// If the value is not present in the input and the allowlist doesn't
	// exist either, this field is not approved so should not be included
	// in the output.
	if (!input_item && !opt_allowlist)
	continue;

	// If the input value doesn't exist, create a fake "input" that we can pass
	// to the merge function. This basically has the effect that the upstream
	// item is taken but not recursively; i.e. any fields which are inside the
	// message/oneof are checked against the allowlist individually. If we just
	// took the whole upstream here, we could add fields which were not
	// allowlisted.
	T input_or_fake;
	if (input_item) {
	input_or_fake = *input_item;
	} else {
	input_or_fake.name = upstream_item.name;
	}

	auto allowlist = opt_allowlist.value_or(AllowlistType{});
	T out_item;
	auto status = Merge(input_or_fake, upstream_item, allowlist, out_item);
	if (!status.ok())
	return status;
	out.emplace_back(std::move(out_item));
	}
	return base::OkStatus();
	}

	base::Status Merge(const ProtoFile::Oneof& input,
	const ProtoFile::Oneof& upstream,
	const Allowlist::Oneof& allowlist,
	ProtoFile::Oneof& out) {
	PERFETTO_CHECK(input.name == upstream.name);
	out.name = input.name;

	// Get the comments from the source of truth.
	out.leading_comments = upstream.leading_comments;
	out.trailing_comments = upstream.trailing_comments;

	// Compute all the fields present in the input but deleted in the
	// source of truth.
	out.deleted_fields = ComputeDeletedByNumber(input.fields, upstream.fields);

	// Finish by merging the list of fields.
	return MergeFields(input.fields, upstream.fields, allowlist, out.fields);
	}

	base::Status Merge(const ProtoFile::Message& input,
	const ProtoFile::Message& upstream,
	const Allowlist::Message& allowlist,
	ProtoFile::Message& out) {
	PERFETTO_CHECK(input.name == upstream.name);
	out.name = input.name;

	// Get the comments from the source of truth.
	out.leading_comments = upstream.leading_comments;
	out.trailing_comments = upstream.trailing_comments;

	// Compute all the values present in the input but deleted in the
	// source of truth.
	out.deleted_enums = ComputeDeletedByName(input.enums, upstream.enums);
	out.deleted_nested_messages =
	ComputeDeletedByName(input.nested_messages, upstream.nested_messages);
	out.deleted_oneofs = ComputeDeletedByName(input.oneofs, upstream.oneofs);
	out.deleted_fields = ComputeDeletedByNumber(input.fields, upstream.fields);

	// Merge any nested enum types.
	out.enums = MergeEnums(input.enums, upstream.enums, allowlist.enums);

	// Merge any nested message types.
	auto status = MergeRecursive(input.nested_messages, upstream.nested_messages,
	allowlist.nested_messages, out.nested_messages);
	if (!status.ok())
	return status;

	// Merge any oneofs.
	status = MergeRecursive(input.oneofs, upstream.oneofs, allowlist.oneofs,
	out.oneofs);
	if (!status.ok())
	return status;

	// Finish by merging the list of fields.
	return MergeFields(input.fields, upstream.fields, allowlist.fields,
	out.fields);
	}

	} // namespace

	base::Status MergeProtoFiles(const ProtoFile& input,
	const ProtoFile& upstream,
	const Allowlist& allowlist,
	ProtoFile& out) {
	// The preamble is taken directly from upstream. This allows private stuff
	// to be in the preamble without being present in upstream.
	out.preamble = input.preamble;

	// Compute all the enums and messages present in the input but deleted in the
	// source of truth.
	out.deleted_enums = ComputeDeletedByName(input.enums, upstream.enums);
	out.deleted_messages =
	ComputeDeletedByName(input.messages, upstream.messages);

	// Merge the top-level enums.
	out.enums = MergeEnums(input.enums, upstream.enums, allowlist.enums);

	// Finish by merging the top-level messages.
	return MergeRecursive(input.messages, upstream.messages, allowlist.messages,
	out.messages);
	}

	} // namespace proto_merger
	} // namespace perfetto