Missing template features and syntaxes

[NullVoxPopuli]

tl;dr: this is a checklist / meta-issue

This is kind of a meta issue tracking everything the community (and myself) wants to add to templates, and without these features, it feels like once you get to a big enough project, you feel pretty limited / have tied hands, if that makes sense. We can expand on the need, use cases, ergonomics, etc in separate issues.

In no particular order,

Features

• Primitives
  • Template string interpolation #623
  • RFRFC remove hash from the Ember lexicon #473
  • array literals (arrays without array helper)
  • object / hash literals (objects without hash helper)
• Built-in helpers
  • Logical helpers renaming #714
  • Adding Logical Operators to Templates #562
  • Adding Numeric Comparison Operators to Templates #561
  • Adding Equality Operators to Templates #560
  • Router Helpers #391
• Destructuring
  • Pre RFC / Feature Request: (De)structuring #553
  • Sugar for multi-assignment with let block helper #602
• Currying Components
  • attributes - Pass attributes to glimmer components when using (component) helper #497
  • modifiers
  • blocks
• User-land template-escape into JS #805
• Spreadable Arguments #593
  • Spread Operator In Templates #184
• Named blocks as arguments
  • Syntax/Feature Need: Passable Blocks (as args / other?) #791
  • Conditional blocks #735
  • Yieldable named blocks #460 (comment)
• Context / component-tree scoped-services
  • Add context-like solution to avoid props drilling #775
  • Error Boundaries
    • "Error boundaries" in Glimmer #513
    • componentDidCatch - preventing the app from breaking when a rendering problem occurs #518
• Pre-RFC: Splat Areas #517
• Argument Default Primitives #695

Consistency

• Loosen restrictions around component argument names #803
• [BUGFIX beta] bind all methods on the router service for use with fn … ember.js#20017
  • Needs generic solution so that we follow JS semantics
• {{else}} should render a value rather than be a control-flow keyword. #917

[machty]

Thank you for compiling and maintaining this <3