Rename assign_wcs "grism" frames to "dispersed"

[stscijgbot-jp]

Issue JP-4185 was created on JIRA by Ned Molter:

Now that MIRI is adding support for a WFSS mode, the names "grism_detector" and "grism_slit" for WFSS-related WCS frames are no longer good names.  MIRI does not have a grism.

This ticket suggests renaming those to "dispersed_detector" and "dispersed_slit".

These names are assigned in the assign_wcs step and the extract_2d step, and called downstream in at least wfss_contam.

For code maintenance reasons, we would like to avoid having multiple names for frames that fundamentally represent the same thing, so we'd like to change these for all modes: NIRISS, NIRCam, and MIRI.

This may have impacts on user or INS workflows if they are accessing transforms or frames of the WCS directly via e.g. wcs.get_transform("grism_detector", "detector")

[stscijgbot-jp]

Comment by Ned Molter on JIRA:

cc Melanie Clarke and Jane Morrison who requested this initially

[stscijgbot-jp]

Comment by David Law on JIRA:

Technically MIRI is a prism not a grism, but I'm not sure that nuance is worth changing the informative 'grism_detector' to 'dispersed_detector'?  Grism immediately tells us that we're working with the WFSS data while 'dispersed' does not.  Does it make more sense just to call both 'grism' even though we know that one is really a prism?

No strong feelings here, but not sure on balance which is least confusing in the long run.

[stscijirahub]

This issue is tracked on JIRA as JP-4185.

[stscijirahub]

Comment by Tyler Pauly on JIRA:

William Jamieson  Here is the proposition to rename frames - aliases could help here.

[stscijirahub]

Comment by William Jamieson on JIRA:

I can add a feature to GWCS which would allow one to specify additional "aliases" for the frame. For example in this case if you wanted to rename the a frame from "foo" to "bar" but preserve the ability to reference the frame using "foo", then one could rename the frame to "bar" and add the alias "foo" to the frame.

wcs.available_frames would only list the actual name of the frame, but in your code all of methods that would retrieve a frame would also honor the alias as well. Note that the wcs will need to enforce that the alias do not overlap with the names or aliases of other frames.

[stscijirahub]

Comment by Ned Molter on JIRA:

Thanks William Jamieson that sounds really useful.  Would it be straightforward to raise a DeprecationWarning when one of the names is used?  (Not saying we would necessarily do so in this case - that could still be discussed.)

[stscijirahub]

Comment by William Jamieson on JIRA:

Its possible, but it will add a fair amount of complexity since I don't think we want GWCS to raise a deprecation warning for an alias by default.

[stscijirahub]

Comment by William Jamieson on JIRA:

Ned Molter here is an implementation for aliasing the frames.

spacetelescope/gwcs#721

[stscijirahub]

Comment by David Law on JIRA:

Setting to On Hold for the time being as I think the confusion coming from renaming these steps, or having multiple names in use outweighs the benefit of the distinction between grism and prism