Messageformat editor

Enable linting

The syntax highlighter is able to handle plain strings,
escaped characters \{ \# \u1234,
wrongly escaped characters \u12z1 \u123 \ } and it recovers from errors.

It highlights multiple consecutive  space characters,
tabs	and trailing space

An interpolated {VAR} variable
A missing {} variable name
A trailing comma {VAR,} after the variable name
SelectFormat: {VAR, select,
  a {a}
  =0 {equal sign in keys is not allowed for selects}
  {missing key}
  x {and the syntax highlighter recovers}
}
PluralFormat: {NUM, plural,
  one {a}
  two {b}
  =10 {10}
  some {another string}
  other {x}
}
selectordinal {NUM, selectordinal,
  other {x}
  =10 {10}
}
user defined functions: {NOW, date} and {NOW, date, full}
The linter marks PluralFormats and SelectFormats without "other" key:
{VAR, select,
  male {He}
  female {She}
} and it marks duplicate keys.
nesting: {PERSON_CNT, select,
  unknown {an unknown number of persons}
  other {{PERSON_CNT, plural,
    =0 {no one}
    =0 {noone}
    =2 {two persons}
    one {one person}
    =2 {2 persons}
    other {# persons}
  }}
}