Summary:
## Motivation
The concept behind JSCallInvoker doesn't necessarily have to apply only to the JS thread. On Android, we need to re-use this abstraction to allow execution of async method calls on the NativeModules thread.
Reviewed By: PeteTheHeat
Differential Revision: D17377313
fbshipit-source-id: 3d9075cbfce0b908d800a366947cfd16a3013d1c
Summary: There is a race condition between tearing down the bridge vs CallbackWrapper invoking the wrapped jsi::Function. This means the wrapper can be stale and unsafe to access after the bridge dies. To avoid unsafe access, let's clean it up properly using weak ref.
Reviewed By: RSNara
Differential Revision: D17380360
fbshipit-source-id: f91ce75d945bf8ed0b141c593bcc674ff465aa8c
Summary:
## The Problem
1. `CatalystInstanceImpl` indirectly holds on to the `jsi::Runtime`. When you destroy `CatalystInstanceImpl`, you destroy the `jsi::Runtime`. As a part of reloading React Native, we destroy and re-create `CatalystInstanceImpl`, which destroys and re-creates the `jsi::Runtime`.
2. When JS passes in a callback to a TurboModule method, we take that callback (a `jsi::Function`) and wrap it in a Java `Callback` (implemented by `JCxxCallbackImpl`). This Java `Callback`, when executed, schedules the `jsi::Function` to be invoked on a Java thread at a later point in time. **Note:** The Java NativeModule can hold on to the Java `Callback` (and, by transitivity, the `jsi::Function`) for potentially forever.
3. It is a requirement of `jsi::Runtime` that all objects associated with the Runtime (ex: `jsi::Function`) must be destroyed before the Runtime itself is destroyed. See: https://fburl.com/m3mqk6wt
### jsi.h
```
/// .................................................... In addition, to
/// make shutdown safe, destruction of objects associated with the Runtime
/// must be destroyed before the Runtime is destroyed, or from the
/// destructor of a managed HostObject or HostFunction. Informally, this
/// means that the main source of unsafe behavior is to hold a jsi object
/// in a non-Runtime-managed object, and not clean it up before the Runtime
/// is shut down. If your lifecycle is such that avoiding this is hard,
/// you will probably need to do use your own locks.
class Runtime {
public:
virtual ~Runtime();
```
Therefore, when you delete `CatalystInstanceImpl`, you could end up with a situation where the `jsi::Runtime` is destroyed before all `jsi::Function`s are destroyed. In dev, this leads the program to crash when you reload the app after having used a TurboModule method that uses callbacks.
## The Solution
If the only reference to a `HostObject` or a `HostFunction` is in the JS Heap, then the `HostObject` and `HostFunction` destructors can destroy JSI objects. The TurboModule cache is the only thing, aside from the JS Heap, that holds a reference to all C++ TurboModules. But that cache (and the entire native side of `TurboModuleManager`) is destroyed when we call `mHybridData.resetNative()` in `TurboModuleManager.onCatalystInstanceDestroy()` in D16552730. (I verified this by commenting out `mHybridData.resetNative()` and placing a breakpoint in the destructor of `JavaTurboModule`). So, when we're cleaning up `TurboModuleManager`, the only reference to a Java TurboModule is the JS Heap. Therefore, it's safe and correct for us to destroy all `jsi::Function`s created by the Java TurboModule in `~JavaTurboModule`. So, in this diff, I keep a set of all `CallbackWrappers`, and explicitly call `destroy()` on them in the `JavaTurboModule` destructor. Note that since `~JavaTurboModule` accesses `callbackWrappers_`, it must be executed on the JS Thread, since `createJavaCallbackFromJSIFunction` also accesses `callbackWrappers_` on the JS Thread.
For additional safety, I also eagerly destroyed the `jsi::Function` after it's been invoked once. I'm not yet sure if we only want JS callbacks to only ever be invoked once. So, I've created a Task to document this work: T48128233.
Reviewed By: mdvacca
Differential Revision: D16623340
fbshipit-source-id: 3a4c3efc70b9b3c8d329f19fdf4b4423c489695b
Summary:
## The Problem
1. `CatalystInstanceImpl` indirectly holds on to the `jsi::Runtime`. When you destroy `CatalystInstanceImpl`, you destroy the `jsi::Runtime`. As a part of reloading React Native, we destroy and re-create `CatalystInstanceImpl`, which destroys and re-creates the `jsi::Runtime`.
2. When JS passes in a callback to a TurboModule method, we take that callback (a `jsi::Function`) and wrap it in a Java `Callback` (implemented by `JCxxCallbackImpl`). This Java `Callback`, when executed, schedules the `jsi::Function` to be invoked on a Java thread at a later point in time. **Note:** The Java NativeModule can hold on to the Java `Callback` (and, by transitivity, the `jsi::Function`) for potentially forever.
3. It is a requirement of `jsi::Runtime` that all objects associated with the Runtime (ex: `jsi::Function`) must be destroyed before the Runtime itself is destroyed. See: https://fburl.com/m3mqk6wt
### jsi.h
```
/// .................................................... In addition, to
/// make shutdown safe, destruction of objects associated with the Runtime
/// must be destroyed before the Runtime is destroyed, or from the
/// destructor of a managed HostObject or HostFunction. Informally, this
/// means that the main source of unsafe behavior is to hold a jsi object
/// in a non-Runtime-managed object, and not clean it up before the Runtime
/// is shut down. If your lifecycle is such that avoiding this is hard,
/// you will probably need to do use your own locks.
class Runtime {
public:
virtual ~Runtime();
```
Therefore, when you delete `CatalystInstanceImpl`, you could end up with a situation where the `jsi::Runtime` is destroyed before all `jsi::Function`s are destroyed. In dev, this leads the program to crash when you reload the app after having used a TurboModule method that uses callbacks.
## The Solution
If the only reference to a `HostObject` or a `HostFunction` is in the JS Heap, then the `HostObject` and `HostFunction` destructors can destroy JSI objects. The TurboModule cache is the only thing, aside from the JS Heap, that holds a reference to all C++ TurboModules. But that cache (and the entire native side of `TurboModuleManager`) is destroyed when we call `mHybridData.resetNative()` in `TurboModuleManager.onCatalystInstanceDestroy()` in D16552730. (I verified this by commenting out `mHybridData.resetNative()` and placing a breakpoint in the destructor of `JavaTurboModule`). So, when we're cleaning up `TurboModuleManager`, the only reference to a Java TurboModule is the JS Heap. Therefore, it's safe and correct for us to destroy all `jsi::Function`s created by the Java TurboModule in `~JavaTurboModule`. So, in this diff, I keep a set of all `CallbackWrappers`, and explicitly call `destroy()` on them in the `JavaTurboModule` destructor. Note that since `~JavaTurboModule` accesses `callbackWrappers_`, it must be executed on the JS Thread, since `createJavaCallbackFromJSIFunction` also accesses `callbackWrappers_` on the JS Thread.
For additional safety, I also eagerly destroyed the `jsi::Function` after it's been invoked once. I'm not yet sure if we only want JS callbacks to only ever be invoked once. So, I've created a Task to document this work: T48128233.
Reviewed By: mhorowitz
Differential Revision: D16589168
fbshipit-source-id: a1c0786999c22bef55d416beb0fc40261447a807
Summary:
JSCallInvoker requires a `std::weak_ptr<Instance>` to create. In our C++, `CatalystInstance` is responsible for creating this `Instance` object. This `CatalystInstance` C++ initialization is separate from the `TurboModuleManager` C++ initialization. Therefore, in this diff, I made `CatalystInstance` responsible for creating the `JSCallInvoker`. It then exposes the `JSCallInvoker` using a hybrid class called `JSCallInvokerHolder`, which contains a `std::shared_ptr<JSCallInvoker>` member variable. Using `CatalystInstance.getJSCallInvokerHolder()` in TurboModuleManager.java, we get a handle to this hybrid container. Then, we pass it this hybrid object to `TurboModuleManager::initHybrid`, which retrieves the `std::shared_ptr<JSCallInvoker>` from the `JavaJSCallInvokerHandler`.
There were a few cyclic dependencies, so I had to break down the buck targets:
- `CatalystInstanceImpl.java` depends on `JSCallInvokerHolderImpl.java`, and `TurboModuleManager.java` depends on classes that are packaged with `CatalystInstanceImpl.java`. So, I had to put `JSCallInvokerHolderImpl.java` in its own buck target.
- `CatalystInstance.cpp` depends on `JavaJSCallInvokerHolder.cpp`, and `TurboModuleManager.cpp` depends on classes that are build with `CatalystInstance.cpp`. So, I had to put `JavaJSCallInvokerHolder.cpp` in its own buck target. To make things simpler, I also moved `JSCallInvoker.{cpp,h}` files into the same buck target as `JavaJSCallInvokerHolder.{cpp,h}`.
I think these steps should be enough to create the TurboModuleManager without needing a bridge:
1. Make `JSCallInvoker` an abstract base class.
2. On Android, create another derived class of `JSCallInvoker` that doesn't depend on Instance.
3. Create `JavaJSCallInvokerHolder` using an instance of this new class somewhere in C++.
4. Pass this instance of `JavaJSCallInvokerHolder` to Java and use it to create/instatiate `TurboModuleManager`.
Regarding steps 1 and 2, we can also make JSCallInvoker accept a lambda.
Reviewed By: mdvacca
Differential Revision: D15055511
fbshipit-source-id: 0ad72a86599819ec35d421dbee7e140959a26ab6
Summary:
This is only the core C++ part of TurboModule - moving to github to make integration with existing NativeModules system slightly easier. Other bindings for iOS/Android are not yet ready to move.
Notes:
* TurboModules is not ready to use at the moment.
* Build configuration is not yet provided (cocoapods/.xcodeproj/gradle), just like Fabric.
* No effort was done to make this lib C++17 strictly compliant yet (there will be in the future).
Reviewed By: RSNara
Differential Revision: D13551211
fbshipit-source-id: cd3b458e6746ee9218451962ca65b1ad641a32db
Ramanpreet Nara
Kevin Gozali
Eric Williamson