[dotnet-watch] Auto-restart project on runtime rude edit #51073
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@DustinCampbell ptal |
This was referenced Oct 1, 2025
DustinCampbell
approved these changes
Oct 3, 2025
tmat
changed the title
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Requires #51032 |
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Description
Implements support for auto-restart when runtime rude edit is encountered.
Fixes #48515
Background
Certain Hot Reload edits are applied speculatively - the compiler emits two code paths gated by a runtime check. If the expected code path is executed the edit works as the user intended (the executed code matches the source code) and the application continues executing flawlessly. The other code path throws
HotReloadExceptionwith message that explains why the edit failed.Examples of such edits include renaming a method, changing method signature, changing lambda signature, changing lambda closure, etc. In these cases a new method or lambda is emitted that matches the code, but the application may still hold onto a delegate to the previous version of the method. If such no longer valid delegate is invoked the
HotReloadExceptionis thrown.Change
In this change, the Hot Reload agent loaded into the application process hooks into the
HotReloadExceptionconstructor via a hook added by dotnet/roslyn#79790 when theHotReloadExceptionis emitted into the delta. The exception construction is intercepted, a notification is sent to the host (dotnet-watch/VS/VS Code) and the current thread is suspended (to avoid throwing the exception). When the host receives the notification it triggers auto-restarts of the process.The change refactors the pipe communication to allow for sending the rude edit notification at arbitrary time. Previously the pipe expected serialized sequence of request - response messages. Instead, we now asynchronously read incoming messages in a loop and trigger the corresponding action based on the response type received.
Before
After
Customer Impact
Impacts Hot Reload scenarios for all types of projects but especially Aspire and web app scenarios.
Regression?
Risk
Justification: The impact is limited to dotnet-watch.
Verification
Packaging changes reviewed?