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https://github.com/facebook/react-native.git
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Moti Zilberman
7886abd243
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/42397 Changelog: [Internal] Adds a stub `PageTarget` class to serve as the entry point to the modern CDP backend in React Native. The primary method exposed by `PageTarget` is `connect()` which is designed to fit directly as a connection callback passed to `InspectorPackagerConnection::addPage()`. This constructs a `PageTargetSession` containing a `PageAgent` where the actual CDP message handling/routing will occur. For now, `PageAgent` implements no CDP methods, and always responds with a "not implemented" error. Basic unit tests are included, though we might want to migrate to a more integration-style test suite (with fewer mocks and real bindings to RN) once we've implemented more of the protocol. ## What is a Page In Chrome's implementation of CDP, a Page represents a single browser tab. A Chrome DevTools session connects to one Page at a time (though it can potentially inspect multiple JavaScript contexts owned by that Page, such as those found in frames and workers). In our system, a Page will correspond 1:1 to React Native's concept of a *Host* (implemented as `RCTHost`, `RCTBridge`, `ReactHostImpl` or `ReactInstanceManager`, depending on the platform). In all cases, the Host is the object that has a stable identity across reloads, and manages the lifetime of an *Instance* where the JSVM and other application state lives. There can be multiple Hosts in a React Native process, though this is somewhat unusual; those would be treated as independent "tabs" from the perspective of the debugger. NOTE: The concepts of Target, Session and Agent are new (to this codebase) and are *broadly* inspired by the [corresponding Chromium / V8 concepts](https://chromium.googlesource.com/chromium/src/+/master/third_party/blink/public/devtools_protocol/#Agents_Targets-and-Sessions), though some details differ. ## Next steps Each core platform implementation in React Native (iOS Bridgeless, iOS Bridge, Android Bridgeless, Android Bridge), as well as out-of-tree platforms that want to support the new debugger, will need to create and register a `PageTarget` instance. We'll do this piecemeal in subsequent diffs. We'll also gradually add APIs and logic to `PageTarget` / `PageAgent` to allow us to implement some "interesting" CDP methods - some of them directly (e.g. handling reload commands) and others by dispatching to nested agents (e.g. a JS debugging agent powered by Hermes). Reviewed By: huntie Differential Revision: D50936932 fbshipit-source-id: ebe5856d7badb361d4971dd9aabeb9982f8aed1b
86 lines
2.6 KiB
C++
86 lines
2.6 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#include "PageTarget.h"
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#include "InspectorUtilities.h"
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#include "PageAgent.h"
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#include "Parsing.h"
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#include <folly/dynamic.h>
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#include <folly/json.h>
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#include <memory>
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namespace facebook::react::jsinspector_modern {
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namespace {
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/**
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* A Session connected to a PageTarget, passing CDP messages to and from a
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* PageAgent which it owns.
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*/
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class PageTargetSession {
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public:
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explicit PageTargetSession(std::unique_ptr<IRemoteConnection> remote)
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: remote_(std::make_shared<RAIIRemoteConnection>(std::move(remote))),
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frontendChannel_(
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[remoteWeak = std::weak_ptr(remote_)](std::string_view message) {
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if (auto remote = remoteWeak.lock()) {
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remote->onMessage(std::string(message));
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}
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}),
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pageAgent_(frontendChannel_) {}
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/**
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* Called by CallbackLocalConnection to send a message to this Session's
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* Agent.
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*/
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void operator()(std::string message) {
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cdp::PreparsedRequest request;
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// Messages may be invalid JSON, or have unexpected types.
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try {
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request = cdp::preparse(message);
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} catch (const cdp::ParseError& e) {
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frontendChannel_(folly::toJson(folly::dynamic::object("id", nullptr)(
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"error",
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folly::dynamic::object("code", -32700)("message", e.what()))));
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return;
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} catch (const cdp::TypeError& e) {
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frontendChannel_(folly::toJson(folly::dynamic::object("id", nullptr)(
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"error",
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folly::dynamic::object("code", -32600)("message", e.what()))));
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return;
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}
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// Catch exceptions that may arise from accessing dynamic params during
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// request handling.
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try {
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pageAgent_.handleRequest(request);
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} catch (const cdp::TypeError& e) {
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frontendChannel_(folly::toJson(folly::dynamic::object("id", request.id)(
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"error",
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folly::dynamic::object("code", -32600)("message", e.what()))));
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return;
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}
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}
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private:
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// Owned by this instance, but shared (weakly) with the frontend channel
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std::shared_ptr<RAIIRemoteConnection> remote_;
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FrontendChannel frontendChannel_;
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PageAgent pageAgent_;
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};
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} // namespace
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std::unique_ptr<ILocalConnection> PageTarget::connect(
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std::unique_ptr<IRemoteConnection> connectionToFrontend) {
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return std::make_unique<CallbackLocalConnection>(
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PageTargetSession(std::move(connectionToFrontend)));
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}
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} // namespace facebook::react::jsinspector_modern
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