Fix Gen-Vx-Mask to handle named grids and grid specification strings for -type grid

[JohnHalleyGotway]

Describe the Enhancement

While developing commands to enhance the online tutorial for gen_vx_mask, we ran into two commands that we expected to work that do not. The usage statement indicates that calling gen_vx_mask in this way should work. This issue is to fix gen_vx_mask to handle the following:

• Run with "-type grid" where "mask_file" is set to a named grid.

gen_vx_mask G004 G130 named_grid_mask.nc -type grid
ERROR  : grd_file_type() -> file does not exist "G130"

• Run with "-type grid" where "mask_file" is set to a grid specification string.

gen_vx_mask G004 "latlon 200 100 -40 -50 0.5 0.5" grid_spec_mask.nc -type grid
ERROR  : grd_file_type() -> file does not exist "latlon 200 100 -40 -50 0.5 0.5"

Here's a selection from the gen_vx_mask usage statement:

"mask_file" defines the masking information (required).
...
For "grid" masking, specify a named grid, the path to a gridded data file, or an explicit grid specification.

So the two examples listed above should work! Once fixed, be sure to update unit_gen_vx_mask.xml to include these new variations.

Time Estimate

1 day.

Sub-Issues

Consider breaking the enhancement down into sub-issues.
None needed.

Relevant Deadlines

List relevant project deadlines here or state NONE.

Funding Source

Define the source of funding and account keys here or state NONE.

Define the Metadata

Assignee

• Select engineer(s) or no engineer required: @JohnHalleyGotway
• Select scientist(s) or no scientist required: no scientist needed

Labels

• Select component(s)
• Select priority
• Select requestor(s)

Projects and Milestone

• Select Repository and/or Organization level Project(s) or add alert: NEED PROJECT ASSIGNMENT label
• Select Milestone as the next official version or Future Versions

Define Related Issue(s)

Consider the impact to the other METplus components.

• METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy
  No impacts.

Enhancement Checklist

See the METplus Workflow for details.

• Complete the issue definition above, including the Time Estimate and Funding Source.
• Fork this repository or create a branch of develop.
  Branch name: feature_<Issue Number>_<Description>
• Complete the development and test your changes.
• Add/update log messages for easier debugging.
• Add/update unit tests.
• Add/update documentation.
• Push local changes to GitHub.
• Submit a pull request to merge into develop.
  Pull request: feature <Issue Number> <Description>
• Define the pull request metadata, as permissions allow.
  Select: Reviewer(s) and Linked issues
  Select: Repository level development cycle Project for the next official release
  Select: Milestone as the next official version
• Iterate until the reviewer(s) accept and merge your changes.
• Delete your fork or branch.
• Close this issue.

[JohnHalleyGotway]

I tweaked the logic in gen_vx_mask to support this. The 2 commands listed in the issue now run fine:

1. Using a named grid:

gen_vx_mask G004 G130 named_grid_mask.nc -type grid -v 3
DEBUG 1: Input Grid:		G004
DEBUG 1: Mask File:		G130
DEBUG 3: Use input grid named "G004".
DEBUG 2: Parsed Input Grid:	G004 (720 x 361)
DEBUG 3: Use mask grid named "G130".
DEBUG 2: Parsed Mask Grid:	G130 (451 x 337)
DEBUG 3: Grid Masking:		10716 of 259920 points inside
DEBUG 1: Output File:		named_grid_mask.nc

2. Using a grid spec string:

gen_vx_mask G004 "latlon 200 100 -40 -50 0.5 0.5" grid_spec_mask.nc -type grid -v 3
DEBUG 1: Input Grid:		G004
DEBUG 1: Mask File:		latlon 200 100 -40 -50 0.5 0.5
DEBUG 3: Use input grid named "G004".
DEBUG 2: Parsed Input Grid:	G004 (720 x 361)
DEBUG 3: Use mask grid defined by string "latlon 200 100 -40 -50 0.5 0.5".
DEBUG 2: Parsed Mask Grid:	To (latlon) (200 x 100)
DEBUG 3: Grid Masking:		20000 of 259920 points inside
DEBUG 1: Output File:		grid_spec_mask.nc