fix(littlefs): Use VFSImpl::exists() to avoid false error log

[BlueAndi]

Description of Change

Use exists() from VFSImpl base class and avoid using open() to check whether the file exists, because open() will log an error in case a file doesn't exists which is confusing, but might be relevant in case a developer uses open() directly and expects that the file is there.

Related links

Closes #7615

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👋 Hello BlueAndi, we appreciate your contribution to this project!

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Memory usage test (comparing PR against master branch)

The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.

Memory	FLASH [bytes]		FLASH [%]		RAM [bytes]		RAM [%]
Target	DEC	INC	DEC	INC	DEC	INC	DEC	INC
ESP32S3	:green_heart: -84	0	:green_heart: -0.02	0.00	0	0	0.00	0.00
ESP32S2	:green_heart: -76	0	:green_heart: -0.02	0.00	0	0	0.00	0.00
ESP32C3	:green_heart: -48	0	:green_heart: -0.01	0.00	0	0	0.00	0.00
ESP32C6	:green_heart: -48	0	:green_heart: -0.02	0.00	0	0	0.00	0.00
ESP32H2	:green_heart: -50	0	:green_heart: -0.02	0.00	0	0	0.00	0.00
ESP32	:green_heart: -84	0	:green_heart: -0.02	0.00	0	0	0.00	0.00

Click to expand the detailed deltas report [usage change in BYTES]

Target	ESP32S3		ESP32S2		ESP32C3		ESP32C6		ESP32H2		ESP32
Example	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM
FFat/examples/FFat_Test	:green_heart: -56	0	:green_heart: -56	0	0	0	0	0	0	0	:green_heart: -56	0
FFat/examples/FFat_time	:green_heart: -56	0	:green_heart: -56	0	0	0	0	0	-	-	:green_heart: -56	0
LittleFS/examples/LITTLEFS_test	:green_heart: -80	0	:green_heart: -72	0	:green_heart: -42	0	:green_heart: -42	0	:green_heart: -50	0	:green_heart: -80	0
LittleFS/examples/LITTLEFS_time	:green_heart: -84	0	:green_heart: -76	0	:green_heart: -48	0	:green_heart: -48	0	-	-	:green_heart: -84	0

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Test Results

 56 files   -  83   56 suites   - 83   4m 53s :stopwatch: - 1h 37m 52s  21 tests  -   9   21 :white_check_mark:  -   9  0 :zzz: ±0  0 :x: ±0  135 runs   - 168  135 :white_check_mark:  - 168  0 :zzz: ±0  0 :x: ±0 

Results for commit 22dfbfee. ± Comparison against base commit 396def3f.

This pull request removes 9 tests.

performance.coremark.test_coremark ‑ test_coremark
performance.fibonacci.test_fibonacci ‑ test_fibonacci
performance.psramspeed.test_psramspeed ‑ test_psramspeed
performance.ramspeed.test_ramspeed ‑ test_ramspeed
performance.superpi.test_superpi ‑ test_superpi
test_touch_errors
test_touch_interrtupt
test_touch_read
validation.periman.test_periman ‑ test_periman

:recycle: This comment has been updated with latest results.

[me-no-dev]

I think the proper action here would be to make the error a warning or even debug.

[BlueAndi]

I think the proper action here would be to make the error a warning or even debug.

This could be done additional. But I would not expext any log by using exists.

[me-no-dev]

If you remove the method, then exists will stop functioning correctly. The log is there to let you know that the file was not found and will not be created. If the log is the issue, then that is where it should be fixed.

[igrr]

If you remove the method, then exists will stop functioning correctly.

Do you recall what is the issue with ::exists in the base class, https://github.com/espressif/arduino-esp32/blob/0539ebf322cf9b0620d4a8c357ddc284edc87f64/libraries/FS/src/vfs_api.cpp#L104 for LittleFS?

[me-no-dev]

I do not recall, because LittleFS was not implemented by us, but I see it being implemented much the same for the other file systems. Issue here seems the same as https://github.com/espressif/arduino-esp32/issues/6749 though for FFat. @lbernstone do you recall why FFat needs to open the file to check if it exists? If the issue is the error log, I do agree that it's a bit to much to issue an error, where a warning or even debug will suffice for the cases where one will need to get more information.

[BlueAndi]

If you remove the method, then exists will stop functioning correctly.

Didn't realize this in my tests. Whats exactly is the problem by using base class exists method?

[me-no-dev]

@lucasssvaz can you please test this same solution with LittleFS, FFat and SPIFFS?

[ioviedodev]

I experiment the same issue in arduino esp32 version 3.0.4 as component idf with version 5.1.4

[aeljandro2]

Same here. Been struggling with the and then realized is just a log thing "Seems". Anyway I think supporting littleFS is kinda important.

[lucasssvaz]

@me-no-dev Tested for LittleFS, SPIFFS and FFat. This solution works for LittleFS and FFat. For SPIFFS this error does not appear and when trying this solution it causes exists() to always return true.

[GeorgeIoak]

I have a situation where I'm not able to update the library yet so I was trying to implement a code fix to directly use VFSImpl::exists() in place of fs->exists() which currently throws the error. I've made several attempt at implementing it but it's always returning false even if the file exists. This is what I had to do to get it to compile so I'm thinking I've botched this up and perhaps someone can help fix it who knows better.

bool IHPFirmware::doesFirmwareFileExist() {
    VFSImpl* vfsImpl = reinterpret_cast<VFSImpl*>(this->deps.fs);
    return vfsImpl->VFSImpl::exists(this->firmwarePath);
}

I confirmed that I'm passing the same path as I was using with fs->exists()

Sorry for asking here but I wasn't sure where else would be appropriate to ask