Rule Enhancement Proposal: autofix for prefer-template

prefer-template is warning concatenations of between strings and expressions. If the rule supports autofix, it’s very helpful to us since we need many steps to fix the code.

1. If there is or${` in the string, escapes it:
   • → \
   • ${ → \${
2. Replaces the concatenation by a template curly:
   • " + expression + " → ${expression}
   • " + expression → ${expression}"
   • expression + " → "${expression}
   • If there are line terminators around the +s, should keep those to inside of template curlies.
   • If the expression is enclosed parentheses, should remove the parentheses.
     • " + (a + 1) + " → ${a + 1}
3. Replaces the enclosing "/' by `.

Examples:

"hello, " + name + "."
// ↓
`hello, ${name}.`

"hello, " + name
// ↓
`hello, ${name}`

"favorites: " + favorites.map(f => {
    return f.name
}) + ";"
// ↓
`favorites: ${favorites.map(f => {
    return f.name
})};`

"favorites: " + 
    favorites.map(f => {
        return f.name
    }) + 
    ";"
// ↓
`favorites: ${
    favorites.map(f => {
        return f.name
    })
};`

[not-an-aardvark]

Looking at the examples, it seems inconsistent to do this:

"hello, " + name + "."
// ↓
`hello, ${name}.` // the whitespace before and after the + sign is removed

"hello, " +
  name + "."
// ↓
`hello, ${
  name}.` // the newline after the + sign is not removed

Instead, maybe it would be better to keep all the whitespace around the plus sign:

"hello, " + name + "."
// ↓
`hello, ${  name  }.`

Then template-curly-spacing can fix the whitespace if necessary.

(Admittedly, most people will probably want their code to look more like hello, ${name} than hello, ${ name }, but in my opinion keeping the whitespace seems like the more consistent thing to do. Alternatively, I guess we could make an exception for spaces surrounding plus signs since they’re a fairly common case.)

[mysticatea]

Yes.