Spellchecker

This extension provides a CodeMirror overlay mode to highlight incorrectly spelled words in Markdown and Raw cells:

It was inspired in part by NextStepWebs/codemirror-spell-checker at the suggestion of @JanSchulz.

Spellchecking

The actual spellchecking is performed by the Typo.js library, which is included as a dependency, with its own license. Typo.js allows the use of hunspell-style dictionaries in a javascript-based spellchecker.

Dictionaries

The dictionaries used by the extension are fetched according to the parameters. To keep this repository lightweight, no dictionaries are incuded, and by default the extension fetches an en_US dictionary from a cdn. However, you can also add your own dictionaries for other languages, or to remove dependency on the cdn. To use your own dictionary, you’ll need to alter the .aff and .dic urls in the extension config. The urls can be relative (for files on your jupyter server) or absolute (for files hosted elsewhere, e.g. on a cdn like the defaults).

This is probably easiest to understand with some explicit examples. Let’s say I want to install a de_DE dictionary. I can get the hunspell files from anywhere I like, but in this example I’m going to use ones listed in the chromium source distribution, which includes quite a lot of different languages. I place my dictionary .aff and .dic files inside the nbextension, such that the directory structure looks like the following:

spellchecker/
    README.md
    config.yaml
    main.css
    main.js
    screenshot.png
    typo/
        LICENSE.txt
        typo.js
        dictionaries/
            de_DE.aff
            de_DE.dic

Then, I need to set the urls in the config to give the location of the dictinaries relative to the spellchecker/main.js file and starting with ./. So, in this case, I would use ./typo/dictionaries/de_DE.aff and ./typo/dictionaries/de_DE.dic.

If you’ve installed the nbextension in the usual place (that is, the per-user jupyter_data_dir() as done by the repo installation script), you can use the following python snippet with the appropriate language code to fetch and save the appropriate files, and configure the extension to use the newly-installed language:

from __future__ import print_function
import os.path
import sys
import base64
from jupyter_core.paths import jupyter_data_dir
from notebook.services.config import ConfigManager

try:
    from urllib.request import urlopen # Py3
    from urllib.parse import urljoin
except ImportError:
    from urllib import urlopen # Py2
    from urlparse import urljoin

cm = ConfigManager()

remote_base_url = 'https://chromium.googlesource.com/chromium/deps/hunspell_dictionaries/+/master'
local_base_url = os.path.join(jupyter_data_dir(), 'nbextensions', 'spellchecker', 'typo', 'dictionaries')

lang_code = 'de_DE'

for ext in ('dic', 'aff'):
    dict_fname = lang_code + '.' + ext
    remote_path = remote_base_url + '/' + dict_fname + '?format=TEXT'
    local_path = os.path.join(local_base_url, dict_fname)

    print('saving {!r}\n    to {!r}'.format(remote_path, local_path))
    with open(local_path, 'wb') as loc_file:
        base64.decode(urlopen(remote_path), loc_file)
    rel_path = './typo/dictionaries/' + dict_fname
    cm.update('notebook', {'spellchecker': {ext + '_url': rel_path}})

cm.update('notebook', {'spellchecker': {'lang_code': lang_code}})

The above is also included as part of the nbextension, and should be available here.

Internals

Any mispelled word has the css class cm-spell-error applied to it, so you can customize their styling in cutom.css if you’d like.