fix: trigger condition cache expressions correctly

[chon219]

Fixes #3356

Description

OnCondition.getExpression() was caches the root expression, but all of the children which override getExpression() were not. This means all child conditions which overrode getExpression() were calling Expression.parse() on EVERY call.

Specific Changes

• Changed getExpression() documentation to state that it must return CACHED expression
• Moved all of the creation logic to protected method createExpression(). This should be backward compatible with classes which do override this method but creates a pattern that causes correct behavior for all OnCondition classes written in the future.
• Changed all of our OnCondition classes from public getExpression() => protected createExpression()

Testing

[coveralls]

Pull Request Test Coverage Report for Build 620406469

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 201 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.2%) to 84.923%

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Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-dialogs-adaptive/src/selectors/trueSelector.ts	1	90.48%
libraries/botbuilder-dialogs-adaptive/src/conditions/onCondition.ts	7	87.5%
libraries/botbuilder-dialogs-adaptive/src/adaptiveDialog.ts	193	38.17%

Totals
Change from base Build 614831139:	0.2%
Covered Lines:	18636
Relevant Lines:	20913

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💛 - Coveralls

[joshgummersall]

All looks good to me. Was this an issue found during Composer testing?

[joshgummersall]

👍

[chon219]

All looks good to me. Was this an issue found during Composer testing?

No, I was porting #3320 and found that we have not ported the latest getExpression/createExpression changes from C#.