Replace jeremeamia/superclosure with opis/closure

[phil-davis]

Description

jeremeamia/superclosure library is no longer maintained and is only officially tested up to PHP 7.2.
https://github.com/jeremeamia/super_closure/blob/master/README.md

Replace it with the recommended https://github.com/opis/closure library.

composer update
Loading composer repositories with package information
Updating dependencies (including require-dev)
Package operations: 1 install, 0 updates, 3 removals
  - Removing symfony/polyfill-util (v1.15.0)
  - Removing symfony/polyfill-php56 (v1.15.0)
  - Removing jeremeamia/superclosure (2.4.0)
  - Installing opis/closure (3.5.1): Loading from cache

This happens to also get rid of some symfony/polyfill dependencies.
And means we are using a dependency that is officially tested on PHP 7.3 and 7.4

How Has This Been Tested?

CI and local run of unit tests:

make test-php-unit TEST_PHP_SUITE=tests/lib/Command/AsyncBusTest.php

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE

[codecov]

Codecov Report

Merging #37238 into master will increase coverage by 0.00%.
The diff coverage is 87.50%.

@@            Coverage Diff            @@
##             master   #37238   +/-   ##
=========================================
  Coverage     64.92%   64.92%           
- Complexity    19148    19149    +1     
=========================================
  Files          1267     1267           
  Lines         74895    74896    +1     
  Branches       1331     1331           
=========================================
+ Hits          48626    48627    +1     
  Misses        25877    25877           
  Partials        392      392           

Flag	Coverage Δ	Complexity Δ
#javascript	54.14% <ø> (ø)	0.00 <ø> (ø)
#phpunit	66.12% <87.50%> (+<0.01%)	19149.00 <0.00> (+1.00)

Impacted Files	Coverage Δ	Complexity Δ
lib/private/Command/ClosureJob.php	87.50% <85.71%> (+4.16%)	3.00 <0.00> (+1.00)
lib/private/Command/AsyncBus.php	91.66% <100.00%> (-0.23%)	19.00 <0.00> (ø)

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[VicDeo]

compare result with false to avoid getClosure() on false below?

[phil-davis]

I used method_exists because it is also nice to know that the unserialized "thing" is an object that has the required method. I checked that if $serializedClosure is not even an object (e.g. is false or "abc" or...) then method_exists happily returns false.