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08e0030032
The impl package currently supports wrapping legacy v1 enums and messages so that they implement the v2 reflective APIs. This functionality is necessary for v1 and v2 to interoperate. However, the existence of this functionality presents several problems: * A significant portion of the complexity in impl is for legacy wrapping. * This complexity is linked into a Go binary even if all the other messages in the binary natively support v2 reflection. * It presents a cyclic dependency when trying to generate descriptor proto. Suppose you are generating descriptor.proto. The generated code would want to depend on the impl package because impl is the runtime implementation for protobuf messages. However, impl currently depends depends on descriptor in order to wrap legacy enum and messages since it needs the ability to dynamically create new protobuf descriptor types. In the case of descriptor.proto, it would presumably be generated with native reflection support, so the legacy wrapping logic is unneccessary. To break the dependency of impl on descriptor, we move the legacy support logic to a different package and instead add hooks in impl so that legacy support could be dynamically registered at runtime. This is dependency injection. Change-Id: I01a582908ed5629993f6699e9bf2f4bee93857a4 Reviewed-on: https://go-review.googlesource.com/c/151877 Reviewed-by: Herbie Ong <herbie@google.com>
18 lines
622 B
Go
18 lines
622 B
Go
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package impl
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import pvalue "github.com/golang/protobuf/v2/internal/value"
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// TODO: Add a default LegacyWrapper that panics with a more helpful message?
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var legacyWrapper pvalue.LegacyWrapper
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// RegisterLegacyWrapper registers a set of constructor functions that are
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// called when a legacy enum or message is encountered that does not natively
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// support the protobuf reflection APIs.
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func RegisterLegacyWrapper(w pvalue.LegacyWrapper) {
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legacyWrapper = w
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}
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