Monaco language definition for apex. Still needs inline SOQL.

apex.js

// Language definition for Apex
return {
  // Set defaultToken to invalid to see what you do not tokenize yet
  // defaultToken: 'invalid',
  keywords: [
    'abstract', 'continue', 'for', 'new', 'switch', 'assert', 'default',
    'goto', 'package', 'synchronized', 'boolean', 'do', 'if', 'private',
    'this', 'break', 'double', 'implements', 'protected', 'throw', 'byte',
    'else', 'import', 'public', 'throws', 'case', 'enum', 'instanceof', 'return',
    'transient', 'catch', 'extends', 'int', 'short', 'try', 'char', 'final',
    'interface', 'static', 'void', 'class', 'finally', 'long', 'strictfp',
    'volatile', 'const', 'float', 'native', 'super', 'while', 'true', 'false',
    'with', 'sharing', 'without', 'global', 'virtual', 'override',
    'update', 'insert', 'delete', 'upsert', 'undelete'
  ],

  typeKeywords: [
    'boolean', 'double', 'byte', 'int', 'short', 'char', 'void', 'long', 'float'
  ],

  operators: [
    '=', '>', '<', '!', '~', '?', ':',
    '==', '<=', '>=', '!=', '&&', '||', '++', '--',
    '+', '-', '*', '/', '&', '|', '^', '%', '<<',
    '>>', '>>>', '+=', '-=', '*=', '/=', '&=', '|=',
    '^=', '%=', '<<=', '>>=', '>>>='
  ],

  // we include these common regular expressions
  symbols:  /[=><!~?:&|+\-*\/\^%]+/,
  escapes:  /\\(?:[abfnrtv\\"']|x[0-9A-Fa-f]{1,4}|u[0-9A-Fa-f]{4}|U[0-9A-Fa-f]{8})/,

  // The main tokenizer for our languages
  tokenizer: {
    root: [
      // identifiers and keywords
      [/[a-z_$][\w$]*/, { cases: { '@typeKeywords': 'keyword',
                                   '@keywords': 'keyword',
                                   '@default': 'identifier' } }],
      [/[A-Z][\w\$]*/, 'type.identifier' ],  // to show class names nicely

      // whitespace
      { include: '@whitespace' },

      // delimiters and operators
      [/[{}()\[\]]/, '@brackets'],
      [/[<>](?!@symbols)/, '@brackets'],
      [/@symbols/, { cases: { '@operators': 'operator',
                              '@default'  : '' } } ],

      // @ annotations.
      // As an example, we emit a debugging log message on these tokens.
      // Note: message are supressed during the first load -- change some lines to see them.
      [/@\s*[a-zA-Z_\$][\w\$]*/, { token: 'annotation', log: 'annotation token: $0' }],

      // numbers
      [/\d*\.\d+([eE][\-+]?\d+)?[fFdD]?/, 'number.float'],
      [/0[xX][0-9a-fA-F_]*[0-9a-fA-F][Ll]?/, 'number.hex'],
      [/0[0-7_]*[0-7][Ll]?/, 'number.octal'],
      [/0[bB][0-1_]*[0-1][Ll]?/, 'number.binary'],
      [/\d+[lL]?/, 'number'],

      // delimiter: after number because of .\d floats
      [/[;,.]/, 'delimiter'],

      // strings
      [/"([^"\\]|\\.)*$/, 'string.invalid' ],  // non-teminated string
      [/'([^'\\]|\\.)*$/, 'string.invalid' ],  // non-teminated string
      [/"/,  'string', '@string."' ],
      [/'/,  'string', '@string.\'' ],
    ],

    whitespace: [
      [/[ \t\r\n]+/, 'white'],
      [/\/\*/,       'comment', '@comment' ],
      [/\/\/.*$/,    'comment'],
    ],

    comment: [
      [/[^\/*]+/, 'comment' ],
      // [/\/\*/, 'comment', '@push' ],    // nested comment not allowed :-(
      [/\/\*/,    'comment.invalid' ],
      ["\\*/",    'comment', '@pop'  ],
      [/[\/*]/,   'comment' ]
    ],

    string: [
      [/[^\\"']+/, 'string'],
      [/@escapes/, 'string.escape'],
      [/\\./,      'string.escape.invalid'],
      [/["']/,     { cases: { '$#==$S2' : { token: 'string', next: '@pop' },
                              '@default': 'string' }} ]
    ],
  },
};

Cursory observations:

1. How are we dealing with the case-insensitive nature of Apex (if we are dealing with this at all)
2. I think right now you are supporting double quotes as string, which is not part of Apex
3. You are missing some types like Decimal.