Share the web workflow MDNS object with the user

[tannewt]

Fixes #7369

@anecdata Mind testing and reviewing?

[anecdata]

Adafruit CircuitPython 8.0.0-beta.6-36-gc93d6d5e6 on 2023-01-12; Adafruit QT Py ESP32S2 with ESP32S2

🟢 ESP32-S2 (QT Py) - Web Workflow ENABLED

Code from #7326 runs, and finds other CircuitPython mDNS devices

🔴 ESP32-S2 (QT Py) - Web Workflow NOT ENABLED

Code from #7326 starts to run, but board enters Safe Mode early, timing doesn't seem exactly consistent:

[tio 21:16:34] Connected
=========================
Starting mDNS server...
Connecting to wifi AP... IPv4=192.168.6.161
-------------------------
Finding mDNS hosts from 192.168.6.161...

[tio 21:16:52] Disconnected
[tio 21:16:54] Connected
Auto-reload is off.
Running in safe mode! Not running saved code.

You are in safe mode because:
CircuitPython core code crashed hard. Whoops!
Crash into the HardFault_Handler.
Please file an issue with the contents of your CIRCUITPY drive at 
https://github.com/adafruit/circuitpython/issues

Press any key to enter the REPL. Use CTRL-D to reload.

Adafruit CircuitPython 8.0.0-beta.6-36-gc93d6d5e6 on 2023-01-12; Adafruit QT Py ESP32S2 with ESP32S2

or

[tio 21:17:54] Connected
Auto-reload is off.
Running in safe mode! Not running saved code.

You are in safe mode because:
CircuitPython core code crashed hard. Whoops!
Crash into the HardFault_Handler.
Please file an issue with the contents of your CIRCUITPY drive at 
https://github.com/adafruit/circuitpython/issues

or

[tio 21:18:35] Connected
=========================
Starting mDNS server...
Connecting to wifi AP... IPv4=192.168.6.161
-------------------------
[tio 21:18:54] Disconnected

Adafruit CircuitPython 8.0.0-beta.6-36-gc93d6d5e6 on 2023-01-12; Raspberry Pi Pico W with rp2040

🟢 Pico W - Web Workflow ENABLED

Code from #7326 runs, and finds other CircuitPython mDNS devices

🔴 Pico W - Web Workflow NOT ENABLED

Code from #7326 starts to run, but board hangs early, no exception, no safe mode, and no control-C, but timing doesn't seem exactly consistent:

[tio 21:11:53] Connected
=========================
Starting mDNS server...
Connecting to wifi AP.... IPv4=192.168.6.201
-------------------------
Finding mDNS hosts from 192.168.6.201...
[tio 21:12:52] Disconnected

hang... power cycle...

[tio 21:13:00] Connected
=========================
Starting mDNS server...
Connecting to wifi AP.... IPv4=192.168.6.201
-------------------------
Finding mDNS hosts from 192.168.6.201...
[tio 21:23:47] Disconnected

hang... power cycle...

[tio 21:23:54] Connected
=========================
Starting mDNS server...
Connecting to wifi AP... IPv4=192.168.6.201
-------------------------

[anecdata]

Went back to a recent pre-PR version and re-verified that:
Adafruit CircuitPython 8.0.0-beta.6-25-gbb3a1c0a2 on 2023-01-04; Adafruit QT Py ESP32S2 with ESP32S2
will find mDNS devices whether Web Workflow is enabled or not.

Similarly:
Adafruit CircuitPython 8.0.0-beta.6-25-gbb3a1c0a2 on 2023-01-04; Raspberry Pi Pico W with rp2040
will find mDNS devices when Web Workflow is not enabled.

[tannewt]

Thank you so much for the testing! Sounds like I forgot to handle the case where web workflow is compiled in but not enabled.

[tannewt]

@anecdata Thanks for the thorough testing. I've fixed it and tested on ESP32-S3 so far. Will find my Pico W now and follow up once I test it.

[tannewt]

Doesn't look like its fully working on Pico W so don't bother reviewing yet. Thanks!

[tannewt]

Ok, should be good now. 🤞

[jepler]

There's one part of this that is confusing to me and may merit a comment if it's intended. No testing performed.

[anecdata]

Tested the artifacts. mdns.Server finds other CircuitPython mDNS devices on both espressif and raspberrypi, with and without web workflow enabled, after reset and after reload. ✓, ✓, ✓, and ✓... LGTM.

[dhalbert]

Thanks! Didn't test; grateful to @anecdata for testing.