Fix bug preventing raw scans without optional elements from being written

[willsanddrew]

As per the standards for e57 files, several child elements (listed below) are optional, but write_scan_raw fails if they aren't present in the data. The calls to getattr aren't returning the default values but instead are throwing exceptions. To fix this I've refactored these elements to be written out only if they're present in the source data, using the "if [] in data" that other optional elements use.

temperature
relativeHumidity
atmosphericPressure
acquisitionStart_dateTimeValue
acquisitionStart_isAtomicClockReferenced
acquisitionEnd_dateTimeValue
acquisitionEnd_isAtomicClockReferenced

Here's a code snippet that demonstrates the issue, using pump.e57 from the libe57 website:

import pye57

e57 = pye57.E57("pump.e57")
data = e57.read_scan_raw(0)
e57_write = pye57.E57("pump_out.e57", mode="w")
e57_write.write_scan_raw(data, scan_header=e57.get_header(0))

[swell-d]

👍

[gredin]

@davidcaron Is there anything preventing you from merging this pull request? And if so, can I help?

[dancergraham]

Hello this looks pretty easy to do - I should be able to merge it! Do you have a reference to those being optional fields? Adding a test using a very small e57 test file (e.g. heavily subsampled / cut down using cloud compare ?) would be awesome too if possible.

[dancergraham]

ahh the tests fail - can you have a look at why @gredin ?

[dancergraham]

ahh got it - it looks like the required and optional fields are given in table 13 of this document https://cdn.standards.iteh.ai/samples/102656/ef2c1f2f33344506946c5ad65aad924f/ASTM-E2807-11-2019-.pdf

[willsanddrew]

I haven't had time to fully dig into the issue yet, but at a quick glance if looks like the test test_copy_file should be updated to pass if any of those seven optional attributes aren't present. I think putting those checks for optional attributes in a try/except block looking for this exception:pye57.libe57.E57Exception: E57 element path well formed but not defined (ErrorPathUndefined) should catch the error.

Additionally, the asset statements for temperature relativeHumidity and atmosphericPressure on that test aren't currently doing anything, as they're comparing header_written to header_written when the rest of the assert statements are comparing header_written to header.

[dancergraham]

Hah yes good spot with the header written tests!
Yes updating the test to ensure it raises an appropriate exception for data we know to be missing from the test file sounds perfect.