706 make undulator gap writeable i18

[stan-dot]

Fixes #706

needed for i18 #710 and DiamondLightSource/i18-bluesky#4

Instructions to reviewer on how to test:

1. run the undulator_dcm routine for lookup table update
2. Confirm nothing breaks happens

Checks for reviewer

• Would the PR title make sense to a scientist on a set of release notes
• If a new device has been added does it follow the standards
• If changing the API for a pre-existing device, ensure that any beamlines using this device have updated their Bluesky plans accordingly
• Have the connection tests for the relevant beamline(s) been run via dodal connect ${BEAMLINE}

[DiamondJoseph]

needs to be added to all of the undulator device instantiations

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.51%. Comparing base (c3ad7e4) to head (6a39c89).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #721      +/-   ##
==========================================
- Coverage   94.52%   94.51%   -0.01%     
==========================================
  Files         115      115              
  Lines        4621     4633      +12     
==========================================
+ Hits         4368     4379      +11     
- Misses        253      254       +1     

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[DominicOram]

The undulator is used in i04_1, i22 and p38 so we would need to add lookup paths there too.

The undulator was originally like this but @callumforrester changed it at #461 (comment) to "make the read-only case simpler". Do we still have a requirement for this to be read-only in some cases? Is this to do Adjust undulator gap to using current lookup table for initial Bragg angle in DiamondLightSource/i18-bluesky#12 (comment)? In which case you could leave it in the undulator_dcm and just set the undulator_dcm device to the current energy and it should correct the undulator with the correct gap?

[stan-dot]

         raise AccessError("Undulator gap access is disabled. Contact Control Room")

that is the not covered line. while I thought that this test tests/devices/unit_tests/test_undulator.py already covers it

@DominicOram perhaps you see something I don't about the behavior of the device here?

[DominicOram]

@DominicOram perhaps you see something I don't about the behavior of the device here?

Odd, I agree it looks like it's tested. I think it's fine to not worry about it. You're still at high coverage

[DominicOram]

Great, thanks. Minor points, mostly take them or leave them other than @DiamondJoseph's point that i22/p38 still need a lookup table

[DominicOram]

Sorry, meant request changes based on the i22 issue