Question

I just asked the support guys on GitHub why AspectJ (*.aj) files are not syntax-highlighted. The answer was that they are using Pygments, but are unaware of any existing lexer for AspectJ. I did a quick web search and did not find any either. Has anyone here written one or can point me to a link for an existing one?

Long ago I have written a lexer for Kconfig (Linux kernel configuration) files, but it was rather hard for me because I do not speak Python. So before I start torturing my brain again, I thought I should better ask first instead of possibly re-inventing the wheel.

Answer 1

After having created a “copy, paste & modify” solution of JavaLexer initially because I really do not speak Python, I managed to hack another quick’n’dirty solution which subclasses JavaLexer and delegates lexing to it for the most part. Exceptions are

• AspectJ-specific keywords,
• handling of inter-type declarations followed by colons without a space not as Java labels, but as AspectJ keywords plus “:” operator and
• handling of inter-type annotation declarations as AspectJ keywords and not as Java name decorators.

I am sure my little heuristic solution misses some details, but as Andrew Eisenberg said: an imperfect, but working solution is better than a non-existent perfect one:

class AspectJLexer(JavaLexer):
    """
    For `AspectJ <http://www.eclipse.org/aspectj/>`_ source code.
    """

    name = 'AspectJ'
    aliases = ['aspectj']
    filenames = ['*.aj']
    mimetypes = ['text/x-aspectj']

    aj_keywords = [
        'aspect', 'pointcut', 'privileged', 'call', 'execution',
        'initialization', 'preinitialization', 'handler', 'get', 'set',
        'staticinitialization', 'target', 'args', 'within', 'withincode',
        'cflow', 'cflowbelow', 'annotation', 'before', 'after', 'around',
        'proceed', 'throwing', 'returning', 'adviceexecution', 'declare',
        'parents', 'warning', 'error', 'soft', 'precedence', 'thisJoinPoint',
        'thisJoinPointStaticPart', 'thisEnclosingJoinPointStaticPart',
        'issingleton', 'perthis', 'pertarget', 'percflow', 'percflowbelow',
        'pertypewithin', 'lock', 'unlock', 'thisAspectInstance'
    ]
    aj_inter_type = ['parents:', 'warning:', 'error:', 'soft:', 'precedence:']
    aj_inter_type_annotation = ['@type', '@method', '@constructor', '@field']

    def get_tokens_unprocessed(self, text):
        for index, token, value in JavaLexer.get_tokens_unprocessed(self, text):
            if token is Name and value in self.aj_keywords:
                yield index, Keyword, value
            elif token is Name.Label and value in self.aj_inter_type:
                yield index, Keyword, value[:-1]
                yield index, Operator, value[-1]
            elif token is Name.Decorator and value in self.aj_inter_type_annotation:
                yield index, Keyword, value
            else:
                yield index, token, value