hclwrite: Formatter to put spaces before colons

The symmetrical spaces around colons in conditionals are important for
familiarity with C-like languages, so we'll instead accept spaces around
colons in our HCL2-unique "for expression" construct.

hclwrite/format.go

@@ -316,10 +316,6 @@ func spaceAfterToken(subject, before, after *Token) bool {
  }
  return true
 
- case after.Type == hclsyntax.TokenColon:
- // Never spaces before colons
- return false
-
  // In the unlikely event that an interpolation expression is just
  // a single object constructor, we'll put a space between the ${ and
  // the following { to make this more obvious, and then the same

hclwrite/format_test.go

@@ -107,17 +107,21 @@ foo(
 )
 `,
  },
+ {
+ `a?b:c`,
+ `a ? b : c`,
+ },
  {
  `[ [ ] ]`,
  `[[]]`,
  },
  {
- `[for x in y: x]`,
- `[for x in y: x]`,
+ `[for x in y : x]`,
+ `[for x in y : x]`,
  },
  {
- `[for x in [y]: x]`,
- `[for x in [y]: x]`,
+ `[for x in [y] : x]`,
+ `[for x in [y] : x]`,
  },
  {
  `