114 lines
3.7 KiB
Markdown
114 lines
3.7 KiB
Markdown
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hermes-inspector provides a bridge between the low-level debugging API exposed
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by Hermes and higher-level debugging protocols such as the Chrome DevTools
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protocol.
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# Targets
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- chrome: classes that implement the Chrome DevTools Protocol adapter. Sits on
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top of classes provided by the inspector target.
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- detail: utility classes and functions
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- inspector: protocol-independent classes that sit on top of the low-level
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Hermes debugging API.
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# Testing
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Tests are implemented using gtest. Debug logging is enabled for tests, and you
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can get debug logs to show even when tests are passing by running the test
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executable directly:
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```
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$ buck build //xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector:chrome-tests
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$ buck-out/gen/xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector/chrome-tests
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[...]
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```
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You can use standard gtest filters to only execute a particular set of tests:
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```
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$ buck-out/gen/xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector/chrome-tests \
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--gtest_filter='ConnectionTests.testSetBreakpoint'
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```
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You can debug the tests using lldb or gdb:
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```
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$ lldb buck-out/gen/xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector/chrome-tests
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$ gdb buck-out/gen/xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector/chrome-tests
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```
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# Formatting
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Make sure the code is formatted using the hermes clang-format rules before
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committing:
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```
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$ xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector/tools/format
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```
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We follow the clang format rules used by the rest of the Hermes project.
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# Adding Support For New Message Types
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To add support for a new Chrome DevTools protocol message, add the message you
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want to add to tools/message_types.txt, and re-run the message types generator:
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```
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$ xplat/js/react-native-github/packages/react-native/ReactCommon/hermes/inspector/tools/run_msggen
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```
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This will generate C++ structs for the new message type in
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`chrome/MessageTypes.{h,cpp}`.
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You'll then need to:
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1. Implement a message handler for the new message type in `chrome::Connection`.
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2. Implement a public API for the new message type in `Inspector`. This will
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most likely return a `folly::Future` that the message handler in (1) can use
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for chaining.
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3. Implement a private API for the new message type in `Inspector` that performs
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the logic in Inspector's executor. (Inspector.cpp contains a comment
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explaining why the executor is necessary.)
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4. Optionally, implement a method for the new message type in `InspectorState`.
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In most cases this is probably not necessary--one of the existing methods in
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`InspectorState` will work.
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For a diff that illustrates these steps, take a look at D6601459.
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# Testing Integration With Nuclide and Apps
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For now, the quickest way to use hermes-inspector in an app is with Eats. First,
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make sure the packager is running:
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```
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$ js1 run
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```
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Then, on Android, build the fbeats target:
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```
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$ buck install --run fbeats
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```
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On iOS, build the `//Apps/Internal/Eats:Eats` target:
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```
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$ buck install --run //Apps/Internal/Eats:Eats
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```
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You can also build `Eats` in Xcode using `arc focus` if you prefer an
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IDE:
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```
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$ arc focus --force-build \
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-b //Apps/Internal/Eats:Eats \
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cxxreact //xplat/hermes/API:HermesAPI //xplat/hermes/lib/VM:VM jsi \
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jsinspector hermes-inspector FBReactKit FBReactModule FBCatalystWrapper \
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//xplat/js:React //xplat/js/react-native-github:ReactInternal
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```
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For all the above commands, if you want to build the inspector `-O0` for better
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debug info, add the argument `--config hermes.build_mode=dbg`.
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You should then be able to launch the app and see it listed in the list of
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Mobile JS contexts in the Nuclide debugger.
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