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Moti ZilbermanandFacebook GitHub Bot
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Summary: Changelog: [Internal] # This diff 1. Provides all Targets with an `executorFromThis()` method, which can be used from within a Target to access a *`this`-scoped main thread executor* = a `std::function` that will execute a callback asynchronously iff the current Target isn't destroyed first. 2. Refactors how (all) Target objects are constructed and retained, from a plain constructor to `static shared_ptr create()`. This is because `executorFromThis()` relies internally on `enable_shared_from_this` plus two-phase construction to populate the executor. 3. Creates utilities for deriving scoped executors from other executors and `shared_ptr`s. The concept is very much like `RuntimeExecutor` in reverse: the #1 use case is moving from the JS thread back to the main thread - where "main thread" is defined loosely as "anywhere it's legal to call methods on Target/Agent objects, access session state, etc". The actual dispatching mechanism is left up to the owner of each `PageTarget` object; for now we only have an iOS integration, where we use `RCTExecuteOnMainQueue`. Coupling the ownership/lifetime semantics with task scheduling is helpful, because it avoids the footgun of accidentally/nondeterministically moving `shared_ptr`s (and destructors!) to a different thread/queue . # This stack I'm refactoring the way the Runtime concept works in the modern CDP backend to bring it in line with the Page/Instance concepts. Overall, this will let us: * Integrate with engines that require us to instantiate a shared Target-like object (e.g. Hermes AsyncDebuggingAPI) in addition to an per-session Agent-like object. * Access JSI in a CDP context (both at target setup/teardown time and during a CDP session) to implement our own engine-agnostic functionality (`console` interception, `Runtime.addBinding`, etc). * Manage CDP execution contexts natively in RN, and (down the line) enable first-class debugging support for multiple Runtimes in an Instance. The core diffs in this stack: * ~~Introduce a `RuntimeTarget` class similar to `{Page,Instance}Target`. ~~ * ~~Make runtime registration explicit (`InstanceTarget::registerRuntime` similar to `PageTarget::registerInstance`). ~~ * ~~Rename the existing `RuntimeAgent` interface to `RuntimeAgentDelegate`.~~ * ~~Create a new concrete `RuntimeAgent` class similar to `{Page,Instance}Agent`.~~ * ~~Provide `RuntimeTarget` and `RuntimeAgent` with primitives for safe JSI access, namely a `RuntimeExecutor` for scheduling work on the JS thread.~~ * Provide RuntimeTarget with mechanism for scheduling work on the "main" thread from the JS thread, for when we need to do more than just send a CDP message (which we can already do with the thread-safe `FrontendChannel`) in response to a JS event. *← This diff* ## Architecture diagrams Before this stack: https://pxl.cl/4h7m0 After this stack: https://pxl.cl/4h7m7 Reviewed By: hoxyq Differential Revision: D53356953 fbshipit-source-id: 152c784eb64e9b217fc2966743b33f61bd8fd97e