xScheduledTask - Fix deletion of scheduled task with unknown or empty task trigger

[matt6697]

Pull Request (PR) description
Fixes deletion of scheduled task with unknown or empty task trigger. Get-TargetResource now returns an empty ScheduleType string if the task trigger is empty or unknown instead of throwing an error.

Tasks like Microsoft\Windows\Application Experience\ProgramDataUpdater don't have a valid ScheduleType for the xScheduledTask DSC resource.

Throwing an error in the Get function is not needed in this case as results of the Get function will be compared with desired state values in the Test function. The empty ScheduledType string will be compared to one the [ValidateSet('Once', 'Daily', 'Weekly', 'AtStartup', 'AtLogOn')] mandatory values of the ScheduledType parameter. The result of the Test function will then be $false and the Set function called to either correct the missing/bad ScheduledType if $ensure='present' or to delete the scheduled task if $ensure='absent'

This Pull Request (PR) fixes the following issues:
Fixes issue #137

Task list:

• Change details added to Unreleased section of CHANGELOG.md?
• Added/updated documentation, comment-based help and descriptions in .schema.mof files where appropriate?
• Examples appropriately updated?
• New/changed code adheres to Style Guidelines?
• Unit and (optional) Integration tests created/updated where possible?

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This change is 

[msftclas]

All CLA requirements met.

[codecov-io]

Codecov Report

Merging #142 into dev will increase coverage by <1%.
The diff coverage is 100%.

@@         Coverage Diff         @@
##           dev   #142    +/-   ##
===================================
+ Coverage   89%    89%   +<1%     
===================================
  Files        5      5            
  Lines      638    638            
===================================
+ Hits       568    570     +2     
+ Misses      70     68     -2

[PlagueHO]

Great job @matt6697- thank you for submitting this. Just a minor suggestion to help with issue diagnosis in future.

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Reviewed 1 of 2 files at r1, 1 of 1 files at r2.
Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks failed.

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Modules/xComputerManagement/DSCResources/MSFT_xScheduledTask/MSFT_xScheduledTask.psm1, line 441 at r2 (raw file):

            default
            {
                $returnScheduleType = ''

Could you also add a verbose log entry to this to state that the trigger type was not specifically handled? I think this info might be useful in diagnosing issues.

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Comments from Reviewable

[matt6697]

Just added the verbose log entry as well as the unit test to avoid regression on this feature.

[matt6697]

Modules/xComputerManagement/DSCResources/MSFT_xScheduledTask/MSFT_xScheduledTask.psm1, line 441 at r2 (raw file):

Previously, PlagueHO (Daniel Scott-Raynsford) wrote…

Could you also add a verbose log entry to this to state that the trigger type was not specifically handled? I think this info might be useful in diagnosing issues.

Done.

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Comments from Reviewable

[PlagueHO]

Awesome stuff @matt6697!

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Reviewed 3 of 3 files at r3.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable