Hang when connecting to a RP2040 with filesystem mounted read-only

[ericzundel]

CircuitPython Version

CircuitPython 9.2.8
Raspberry Pi Pico

Workflow(s)

USB

Browser(s)

Google Chrome Version 138.0.7204.98 (Official Build) (64-bit)
Windows 11

Console Log

index.js:32 Uncaught (in promise) TypeError: Cannot read properties of null (reading 'readOnly')
    at Wu.open (index.js:32:93023)
    at RR.saveFileDialog (index.js:112:6199)
    at RR.saveFileAs (index.js:112:5645)
    at HTMLButtonElement.<anonymous> (index.js:118:11847)


When trying to recreate this, I got some different errors.  The connect attempt suceeded, but saving hung with these errors in the console:

index.js:118 write failed InvalidStateError: An operation that depends on state cached in an interface object was made but the state had changed since it was read from disk. undefined
sy	@	index.js:118
await in sy		
saveFile	@	index.js:112
jb	@	index.js:118
await in jb		
(anonymous)	@	index.js:118
index.js:118 write failed TypeError: Cannot read properties of undefined (reading 'split')
    at PR._splitPath (index.js:115:3146)
    at PR.writeFile (index.js:115:2960)
    at async cT.writeFile (index.js:93:8639)
    at async RR.showBusy (index.js:112:4411)
    at async RR.writeFile (index.js:112:6345)
    at async sy (index.js:118:16147) TypeError: Cannot read properties of undefined (reading 'split')
    at PR._splitPath (https://code.circuitpython.org/assets/js/index.js:115:3146)
    at PR.writeFile (https://code.circuitpython.org/assets/js/index.js:115:2960)
    at async cT.writeFile (https://code.circuitpython.org/assets/js/index.js:93:8639)
    at async RR.showBusy (https://code.circuitpython.org/assets/js/index.js:112:4411)
    at async RR.writeFile (https://code.circuitpython.org/assets/js/index.js:112:6345)
    at async sy (https://code.circuitpython.org/assets/js/index.js:118:16147)
sy	@	index.js:118
setTimeout		
sy	@	index.js:118
await in sy		
saveFile	@	index.js:112
jb	@	index.js:118
await in jb		
(anonymous)	@	index.js:118

Steps

1. Connect the RP2040 device to the computer with USB. I'm using a Raspberry Pi Pico 2.
2. Make sure it's mounted read only. This can happen intermittently if you unplug the pico without ejecting. You can force the drive to be readonly in windows with the diskpart utility:

DISKPART> list disk

  Disk ###  Status         Size     Free     Dyn  Gpt
  --------  -------------  -------  -------  ---  ---
  Disk 0    Online          953 GB      0 B        *
  Disk 1    Online         1024 KB      0 B

DISKPART> select disk 1

Disk 1 is now the selected disk.

DISKPART> attributes disk set readonly

3. Now use the 'Connect' button on the code.circuitpython.org IDE. Sometimes it will connect sucessfully, other times you'll just get part of the flow completed with the first exception:

4. If that succeeds, try editing code.py on the device and saving it. You will get the second set of exceptions as it tries to write the file.

NOTE: That readonly attribute will stick if you unmount and remount the drive. If you are trying to clear the readonly flag, use diskpart again.

DISKPART> select disk 1
DISKPART> attributes disk clear readonly

Description

Looks like the code just doesn't expect read-only filesystems in more than one place. An acceptable solution would to just handle this and pop up an alert. Better would be to give some advice as it can be a common problem when working with novice users. Using Mu, I've had this problem where students don't cleanly eject the Pico and it becomes read-only often. The solution is to remount and properly eject and sometimes run a filesystem check.

Additional information

I am willing to help work on the project if you are looking for contributors. Please hit me up on Discord and we can chat.

I started looking at the IDE and writing up what I'd like to see for use with our students.

[ericzundel]

I found another way to reproduce the same issue (you connect to a device, the green check shows up, but the window stays open and in disconnected state) This time I just tried to connect to a serial port that is some kind of placeholder device on WSL2. There is no indication anything went wrong in the UI or console, but in the stderr from chromium on Linux I see:

[211929:211929:0711/232927.754736:ERROR:components/device_event_log/device_event_log_impl.cc:198] [23:29:27.754] Serial: serial_io_handler.cc:147 Failed to open serial port: FILE_ERROR_ACCESS_DENIED

[ericzundel]

Problem seems to be happening here inside of usb.js: _switchToDevice():

await this._serialDevice.open({baudRate: 115200}); // TODO: Will fail if something else is already connected or it isn't found.

I can see how tricky this while looking at the exception handler in showConnect(). From reading the comments, it seems there are many reasons it could fail (one seems to be that Chrome blocks the port selection dialog if you are using the debugger) and maybe the user just needs to select again. Maybe I can surface this in a status window but keep the dialog running.

Something like this:

[ericzundel]

I proposed a PR to help provide user friendly error messages in #334 but it doesn't solve this problem as the dialog box is already popped down.

Possibly a better solution for problems after the workflow dialog is popped down is to put up a floating status window at the top or bottom of the UI.

[ericzundel]

There is a similar issue to the readonly filesystem issue if you remove the device from your computer without hitting 'Disconnect' first. You get an exception in the console when you try to disconnect and reconnect by pressing hte disconnect button. The Disconnect button doesn't switch modes back to the connect button.