Allow enabling direct debugging through the CLI.

[nasadigital]

Addresses #4316.
Adds a parameter --direct-debugging to the CLI which enables direct debugging by default.
When the parameter is parsed it supplies the property UseDirectDebugging=true to msbuild.
The property defines the USE_DIRECT_DEBUGGING macro for C++ or constant for C#.

Microsoft Reviewers: Open in CodeFlow

[acoates-ms]

The code that uses USE_DIRECT_DEBUGGING is app specific. While it is part of the current default template there is no guarantee that the apps code will include that code, or use it in the same way.

I worry that adding an option like this would be confusing as there are plenty of cases where it wouldn't work. I also worry some about what it does to build caching. How will we know we need to rebuild the binaries.

This isn't an option that is provided to the CLI for android or iOS either.

[asklar]

pls move into the instance settings instead if this is something that can be always enabled in debug builds

[nasadigital]

Thank you for your feedback @acoates-ms!

The code that uses USE_DIRECT_DEBUGGING is app specific. While it is part of the current default template there is no guarantee that the apps code will include that code, or use it in the same way.
I worry that adding an option like this would be confusing as there are plenty of cases where it wouldn't work.

That is correct. Is there a way to set InstanceSettings outside of the app?

I also worry some about what it does to build caching. How will we know we need to rebuild the binaries.

As you mention, my understanding is that you would need to rebuild if you want to toggle the defaults. I was think of maybe using environment variables to switch this without needing to rebuild. What do you think? Are there any more fitting approaches?

This isn't an option that is provided to the CLI for android or iOS either.

Thanks for clarifying. Are you familiar with how would one go about using direct debugging in android or iOS?

[acoates-ms]

The story for direct debugging in Android / iOS is still being worked out. (Its not easy right now).

But for now its similar to enabling various other dev features and involves a code change
https://github.com/react-native-community/rn-diff-purge/blob/b7d5b8decbe2dc4a5159c01b423e2cf0c9f922f9/RnDiffApp/android/app/src/main/java/com/rndiffapp/MainApplication.java#L19

[asklar]

  default: 'x86',

just realized that we don't mention ARM64 but I believe Jon added support for ARM64, consider adding that :)

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Refers to: vnext/local-cli/runWindows/runWindows.js:147 in f48cb5b. [](commit_id = f48cb5b, deletion_comment = False)

[ghost]

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