Include Symbol in ContentValue

[gilest]

Interested to hear thoughts about this.

const example = Symbol('example');

<template>
  {{example}}
</template>

Will render

Symbol(example)

[dfreeman]

You can also write this:

const example = ['hello', 'world'];

<template>
  {{example}}
</template>

And render this:

hello,world

The reason we prohibit both of those cases isn't that you'll get a runtime exception when trying to render the value, it's that values of those types don't typically represent user-consumable information. 9 times out of 10 if we encounter a symbol or object being used directly as template content, it represents a typo or refactoring mistake like accidentally referencing source data instead of the human-formatted version.

TS's types for native language features are full of similar cases to this—the Symbol constructor is a great example. I can write Symbol(['hello', 'world']) and that will coerce the array to a string at runtime without complaint, but TS still flags it as a type error because it represents a probable mistake.

For cases where you do want to coerce an arbitrary value to a string no matter what it is, you can either coerce it in TS and reference the result in the template, or use the concat helper to implicitly perform the coercion for you.

import { concat } from '@ember/helper';

const example = Symbol('example');
const exampleString = example.toString();

// Both of these will render `Symbol(example)` with no type error:
<template>
  {{exampleString}}
  {{concat example}}
</template>

[gilest]

Thanks @dfreeman. Adding Glint types is quite a good shakedown of a public API in this case