pygments-lexer-babylon

A javascript lexer for Pygments that uses the babylon parser

WARNING!

Node.js must be installed to use this package. Set the environment variable PYGMENTS_NODE_COMMAND to the command you use to run Node. The default is nodejs. If the following command works, you are most probably OK:

nodejs -v

Why?

Pygments can not properly highlight new and shiny javascript (particulary jsx). Until all these features are implemented in Pygments, you can use this package as a fallback. Also, it is a good fun to experiment with various technologies 😉.

Install

Nothing too much here, apart from the Node.js dependency:

pip install pygments-lexer-babylon

This will install Pygments for you (>=2.1), so if something depends on an older version, virtualenv is recommended. (Or use docker...)

Usage

The importable name of the package: pygmentslexerbabylon. It provides two lexers: BabylonLexer and BabylonHtmlLexer. The latter is needed because the built in HtmlLexer hard codes the usage of JavascriptLexer between <script> tags.

If you have "manual" control over which lexer to use, do something like this:

from pygments import highlight
from pygments.formatters import HtmlFormatter
from pygmentslexerbabylon import BabylonLexer

lexer = BabylonLexer()  # You select it manually...
formatter = HtmlFormatter(linenos=True, cssclass="source")
code = '<ReactComponent/>'
result = highlight(code, lexer, formatter)

In some cases you do not have control over the selected lexer. Let's say, you use Markdown, which turns out to use code like this:

from pygments.lexers import get_lexer_by_name, guess_lexer

try:
    lexer = get_lexer_by_name(self.lang)
except ValueError:
    try:
        lexer = guess_lexer(self.src)
    except ValueError:
        lexer = get_lexer_by_name('text')

In this case use language name jsx for javascript files and htmlx for html files.

If you use the pygmentize all the above works:

$ pygmentize -l jsx myreact.js  # Note the extension is not jsx
$ pygmentize myreact.jsx
$ pygmentize -l htmlx htmlwithjsx.html
$ pygmentize htmlwithjsx.htmlx

Gotchas

• It is a bit slower than Pygments...
• May fail for really large files (0.5 MB worked for me though)
• Produces slightly different result than the original Pygments lexer