Support `swiftformat:(disable|enable):<scope> (all|<rule>…)` comments

[rgoldberg]

Please Support swiftformat:(disable|enable):<scope> (all|<rule>…) comments, which would disable/enable rules from the appropriate scope.

This will avoid needing to disable then enable (or vice verse).

Potential scopes:

• declaration
• signature
• parameters
• parameter
• statement
• expression

statement

Taking statement as an example:

If the comment is within the middle of (not before or after) a current statement, then statement applies the given disable/enable to everything within the current statement from the comment's line to the end of the current statement.

If the comment is before or after (not within the middle of) a statement:

• if the comment is on the same line as the previous statement, then statement applies the given disable/enable to everything within the previous statement on the comment's line.
• if the comment that the line is on does not contain any of the previous statement, then statement applies the given disable/enable to everything within the next statement within the same block. If there is no next statement within the block, it applies to nothing, and should be flagged with a warning or error.

e.g. (note that the code listed as having rule disabled also include the appropriate whitespace):

// `rule` is disabled only for `let x = [`, `c(),` & `d(),` & the closing `]`
a(); b(); let x = [ // swiftformat:disable:statement rule
  c(),
  d(),
]; e()

// `rule` is disabled only for `c(),`, `d(),` & the closing `]`
a(); let x = [
  b(),
  c(), // swiftformat:disable:statement rule
  d(),
]; e()

// `rule` is disabled only for the closing `]`
a(); let x = [
  b(),
  c(),
  d(),
] // swiftformat:disable:statement rule
e()

// warning/error
{
  a()
 // swiftformat:disable:statement rule
}

// `rule` is disabled only for `b()`
{
  a()
 // swiftformat:disable:statement rule
  b()
}

// `rule` is disabled only for `b()`
{
  a()
  b() // swiftformat:disable:statement rule
  c()
}

// `rule` is disabled only for `b()`
{
  a(); b() // swiftformat:disable:statement rule
  c()
}

// `rule` is disabled only for `b()`
{
  a() +
  b() // swiftformat:disable:statement rule
  c()
}

// `rule` is disabled only for `a() + b()`
{
  a() + // swiftformat:disable:statement rule
  b()
  c()
}

// `rule` is disabled only for `a() + b()`
{
  // swiftformat:disable:statement rule
  a() +
  b()
  c()
}

other scopes

Either each scope could have its own keyword, or maybe scopes where context would provide disambiguation could share keywords (e.g., statement & expression can't be disambiguated by context, and parameters & parameter also can't be disambiguated by context).

We could refine behavior for each scope once we have an exhaustive list of supported scopes, keywords, etc.