Please consider changing behavior of `byBooleanAttrVal`

[charlessuh]

Description

The behavior of the current byBooleanAttrVal returns true or false based on the existence of an attribute. This change renames that behavior to byExistAttrVal.

The new byBooleanAttrVal will return true or false based on the literal string value (e.g. "true" or "false") and will return undefined for other cases, including lack of existence of the attribute.

Related Issue

https://github.com/adobe/react-webcomponent/issues/13

Motivation and Context

If you create a React component with an optional boolean prop that defaults to true, the current behavior of byBooleanAttrVal looks at an attribute being missing and passes an explicit false to the React component, short-circuiting the default handling logic.

It would be desirable in this case to pass undefined to the React component, so the default handling logic works.

How Has This Been Tested?

npm run test

Screenshots (if appropriate):

n/a

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] I have signed the Adobe Open Source CLA.
• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[alexmirea]

Hi Charles!

Thanks for the PR. The byBooleanAttrVal works according to the spec https://html.spec.whatwg.org/multipage/common-microsyntaxes.html#boolean-attributes I don't want to break the API, so what we can do is add a parameter to the byBooleanAttrVal to send undefined when not present, and to document this.