Extending Paperless

Warning

This section is not updated to paperless-ng yet.

For the most part, Paperless is monolithic, so extending it is often best managed by way of modifying the code directly and issuing a pull request on GitHub. However, over time the project has been evolving to be a little more “pluggable” so that users can write their own stuff that talks to it.

Parsers

You can leverage Paperless’ consumption model to have it consume files other than ones handled by default like .pdf, .jpg, and .tiff. To do so, you simply follow Django’s convention of creating a new app, with a few key requirements.

parsers.py

In this file, you create a class that extends documents.parsers.DocumentParser and go about implementing the three required methods:

  • get_thumbnail(): Returns the path to a file we can use as a thumbnail for this document.

  • get_text(): Returns the text from the document and only the text.

  • get_date(): If possible, this returns the date of the document, otherwise it should return None.

signals.py

At consumption time, Paperless emits a document_consumer_declaration signal which your module has to react to in order to let the consumer know whether or not it’s capable of handling a particular file. Think of it like this:

  1. Consumer finds a file in the consumption directory.

  2. It asks all the available parsers: “Hey, can you handle this file?”

  3. Each parser responds with either None meaning they can’t handle the file, or a dictionary in the following format:

{
    "parser": <the class name>,
    "weight": <an integer>
}

The consumer compares the weight values from all respondents and uses the class with the highest value to consume the document. The default parser, RasterisedDocumentParser has a weight of 0.

apps.py

This is a standard Django file, but you’ll need to add some code to it to connect your parser to the document_consumer_declaration signal.

Finally

The last step is to update settings.py to include your new module. Eventually, this will be dynamic, but at the moment, you have to edit the INSTALLED_APPS section manually. Simply add the path to your AppConfig to the list like this:

INSTALLED_APPS = [
    ...
    "my_module.apps.MyModuleConfig",
    ...
]

Order doesn’t matter, but generally it’s a good idea to place your module lower in the list so that you don’t end up accidentally overriding project defaults somewhere.

An Example

The core Paperless functionality is based on this design, so if you want to see what a parser module should look like, have a look at parsers.py, signals.py, and apps.py in the paperless_tesseract module.