feat: botbuilder stdlib

[joshgummersall]

This PR introduces a new package, botbuilder-stdlib, that exports some helpful shared utilities. The type assertion code will provide a robust way to construct type assertions that perform runtime type validation and compile-time type hinting. The result will be more type-safe code and a developer experience that better leverages IntelliSense.

A note for code reviewers: the botframework-schema diff is quite large due to prettier code formatting changes. I performed the code formatting step as a separate commit before adding the new type assertions. Hopefully, that makes this a bit easier to review.

I'm open to feedback on the developer ergonomics for asserting types. Unfortunately, the compiler requires that type assertions functions do not reference type parameters without an explicit type declaration (i.e. assert.arrayOf(assert.string) is not possible without const arrayOfStrings: Assertion<Array<string>> = assert.arrayOf(assert.string)). This means that chaining and other helper functions are basically impossible to write. If you notice some verbose type declarations, that's why.

[stevengum]

Looks good! Two small things in the package.json for botbuilder-stdlib.

[coveralls]

Pull Request Test Coverage Report for Build 401371168

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 153 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.3%) to 84.393%

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Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-core/src/storage.ts	1	90.0%
libraries/botbuilder-azure-blobs/src/blobsStorage.ts	16	28.57%
libraries/botbuilder-azure-blobs/src/blobsTranscriptStore.ts	37	9.95%
libraries/botframework-schema/src/index.ts	99	64.89%

Totals
Change from base Build 401242264:	-0.3%
Covered Lines:	17556
Relevant Lines:	19877

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💛 - Coveralls

[stevengum]

Temporarily blocking PR while we get other feedback

[stevengum]

At the moment I think the doc strings need to be updated with xrefs otherwise the expectation is that the developer is already familiar with the contents of botbuilder-stdlib. I worry a little that a dev might wander in here, use the provided functions and introduce a bug due to expectations on either Node or TypeScript behavior that aren't the exact same as in this library.

This isn't a requirement for this PR as this package is essentially internal, but something to be considered for the future.

What do you think?

[joshgummersall]

That's totally fair - my plan is twofold. First, carefully review the use of the type assertions/tests (especially unsafe). Second, improve the dev experience based on feedback from the team. I'm going to rewrite the assertions to have better JSDoc comments, for now, I think that will provide a good starting place.

[stevengum]

One small suggestion. but otherwise LGTM