Remove usage of Arduino constant emptyString and use our own instead

[mathieucarbou]

This PR is a cleanup in order to use our own empty string constant instead of Arduino one.

This will also help support HOST as done in PR #416

[mathieucarbou]

@MitchBradley FYI

[Copilot]

Pull request overview

This PR replaces uses of the Arduino emptyString constant with a project-owned asyncsrv::empty constant.

Changes:

• Updated default arguments across response/request APIs to use asyncsrv::empty.
• Replaced emptyString assignments/returns throughout request parsing and authentication helpers.
• Updated examples to return/assign asyncsrv::empty instead of emptyString.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
src/WebResponseImpl.h	Switches AsyncBasicResponse String overload default arg to asyncsrv::empty.
src/WebRequest.cpp	Replaces emptyString in parsing/temp fields and several const String& return paths.
src/WebHandlers.cpp	Updates AsyncFileResponse content-type default argument usage.
src/WebAuthentication.cpp	Uses asyncsrv::empty for early-return empty String values on errors.
src/ESPAsyncWebServer.h	Updates multiple overload defaults and const String& accessors to use asyncsrv::empty.
src/AsyncEventSource.cpp	Returns asyncsrv::empty on allocation failure.
examples/Templates/Templates.ino	Updates template processor “no value” return to asyncsrv::empty.
examples/RequestContinuation/RequestContinuation.ino	Clears message using asyncsrv::empty.
examples/ChunkRetryResponse/ChunkRetryResponse.ino	Clears trigger string using asyncsrv::empty.

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[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 5 comments.

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[MitchBradley]

@mathieucarbou Thanks for addressing this. After it is merged, should I close #416 and submit a revised version, after addressing copilot's concerns?

[mathieucarbou-ibm]

@mathieucarbou Thanks for addressing this. After it is merged, should I close #416 and submit a revised version, after addressing copilot's concerns?

You just need to rebase your HOST PR on top of branch emptyString instead of main.

Also please do not forget to open a separate PR for the state machine refactoring. This one is more requires more review and testing.

Thank you very much for these !

[MitchBradley]

One thing that occurred to me is that instead of #if defined(ESP32) || defined(HOST}, it might be better to create a new macro with a name like MULTICORE, so one could write #ifdef MULTICORE and put the "ESP32 || HOST" logic in one place.

[MitchBradley]

Or perhaps a conditionally compiled LOCK macro so one could write

LOCK(_client_queue_lock)

[mathieucarbou]

One thing that occurred to me is that instead of #if defined(ESP32) || defined(HOST}, it might be better to create a new macro with a name like MULTICORE, so one could write #ifdef MULTICORE and put the "ESP32 || HOST" logic in one place.

I am not sure that the content of the conditions only apply to multicore.
They apply to ESP32 and libretiny at the moment because both are really close, compared to 8266 and RPI.

Right now I would leave as it is with the 3 conditions... They are at the moment more linked to the common things provided by these platforms than being multicore or not I think.

[mathieucarbou]

Or perhaps a conditionally compiled LOCK macro so one could write

LOCK(_client_queue_lock)

That's the equivalent of what @willmmiles put in place in AsyncTCP.
But please don't fire in every direction right now.

I would just focus at the Linux/Mac support with HOST macro, then you can open a new PR with the state machine.

And if you are willing to improve how the locking is down using macros, please open another PR.

As long as you keep the work in single isolated unit of work commits and PRs.

Thanks 👍