feat: fast-provider

[nicholasrice]

Description

This PR tracks the work to implement the new Provider system outlined in #3361.

This is a work in progress, so check back frequently to see progress, but please don't feel compelled to leave do a detailed review at this point.

Updates:

1. The Provider concept has been replaced with a general-purpose dependency injection system

Feature checklist

• Add FoundationElement
  • Method to resolve template for instance, resolving from self or provider
  • Method to resolve styles for instance, resolving from self or provider
  • Instance template and styles (provides opportunity to set styles and template for an element instance)
  • Mechanism to resolves nearest provider during connectedCallback()
• Add Provider
  • Tracks parent provider, if any, otherwise null.
  • Can resolve templates for an element instance
  • Can resolve styles for an element instance
  • Arbitrary custom elements can be Provider instance
  • Can register design tokens that reflect to CSS custom properties
  • Can register CSS custom property resolvers that write CSS custom properties that are a product of the provider instance
  • How can this all hook into a general purpose provider mechanism that can be extensible?
• Dependency-injection system
  • Resolution of DI containers through DOM hierarchy
  • Resolution of DI containers not through DOM hierarchy
• DesignTokenLibrary for managing design tokens
  • Subscription to property changes
  • Can create token library hierarchies
  • Can assign "derived" properties, where the property getter returns the product of an evaluate fn. Can establish design token dependencies for a derived property. If a derived property depends on itself (setting a bg color to a product of bg color + others) then the upstream property will always be used during evaluation
  • Read-only token library (w/ decorator to connect to nearest provider library)
• DesignTokenProvider
  • DI container to provide DesignTokenLibraries (read and read/write)
  • Writes design tokens set on instance to CSS Custom properties
  • Can hook up attributes and properties to Design Tokens, as configured by the Configuration This can be done per-provider pretty easily, and in ways that make sense for that provider. I'm not sure global configuration for this is necessary anymore
  • Provides mechanism to assign properties by component state.
• Add Configuration
  • Can construct with a prefix option to be the custom element name prefix
  • Can register a default template for an element name
  • Can register a default stylesheet for an element name
  • Can register a custom element. This would define the element customElements.define()
  • Can register design tokens
    • Map token to a content property
    • Map token to an IDL property
    • Map token to a CSS custom property
    • Associate default value for token
  • Can define a Provider with defineProvider()
  • Can reflect design token CSS custom properties to the body element (optionally, facilitates scenario where authors don't want to wrap UI with a provider element)(investigate impacts of this).
  • Can update a Design Token value to change the default.
• CSSCustomPropertyManager to manage creation of CSSStyleSheet instances for re-use across components.
  • Can get ElementStyles | HTMLStyleElement by custom property key / value
  • DI interface

Issue type checklist

• Chore: A change that does not impact distributed packages.
• Bug fix: A change that fixes an issue, link to the issue above.
• New feature: A change that adds functionality.

Is this a breaking change?

• This change causes current functionality to break.

Adding or modifying component(s) in @microsoft/fast-components checklist

• I have added a new component
• I have modified an existing component
• I have updated the definition file
• I have updated the configuration file

Process & policy checklist

• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

[nicholasrice]

Closing because this PR is no longer relevant. Some of this has been merged in a different form and the other work will be adapted or dropped as necessary.