Support optional input

[pingsutw]

Signed-off-by: Kevin Su [email protected]

TL;DR

flyteorg/flyte#2426

Type

• Bug Fix
• Feature
• Plugin

Are all requirements met?

• Code completed
• Smoke tested
• Unit tests added
• Code documentation added
• Any pending items have an associated Issue

Complete description

Set default input value (None) for optional type in typed_interface

Tracking Issue

https://github.com/flyteorg/flyte/issues/

Follow-up issue

NA
OR
https://github.com/flyteorg/flyte/issues/

[codecov]

Codecov Report

Merging #989 (6740aff) into master (53d31c2) will increase coverage by 0.04%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##           master     #989      +/-   ##
==========================================
+ Coverage   86.50%   86.55%   +0.04%     
==========================================
  Files         267      268       +1     
  Lines       24795    24960     +165     
  Branches     2787     2812      +25     
==========================================
+ Hits        21450    21604     +154     
- Misses       2868     2877       +9     
- Partials      477      479       +2     

Impacted Files	Coverage Δ
tests/flytekit/unit/core/test_interface.py	85.71% <90.90%> (+0.30%)	⬆️
tests/flytekit/unit/core/test_composition.py	98.62% <96.00%> (-0.58%)	⬇️
flytekit/core/interface.py	83.77% <100.00%> (+0.43%)	⬆️
flytekit/core/promise.py	76.75% <100.00%> (+0.51%)	⬆️
flytekit/core/type_engine.py	85.17% <100.00%> (+0.20%)	⬆️
flytekit/clients/friendly.py	55.39% <0.00%> (-1.75%)	⬇️
flytekit/types/structured/structured_dataset.py	92.89% <0.00%> (-1.40%)	⬇️
flytekit/models/node_execution.py	76.64% <0.00%> (-0.81%)	⬇️
flytekit/clients/raw.py	64.46% <0.00%> (-0.28%)	⬇️
flytekit/configuration/__init__.py	94.96% <0.00%> (-0.04%)	⬇️
... and 11 more

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[eapolinario]

Can you add a few more tests to cover the explicit use of Union and also the collection literal types (i.e. maps and lists)?