jrnl/docs/plugins.md

Creating Importer and Exporter Plugins

You can extend jrnl with custom importer and exporter plugins. Importer plugins add new ways to import data into jrnl, while exporter plugins add new ways to change the output of jrnl, whether to make data available to other programs or just view entries differently in the console.

Both types of plugins use native namespace packages. Once they are installed, they should be available to jrnl when using the same Python interpreter that was used to install them.

!!! tip To confirm that a plugin is present, run jrnl --diagnostic

Getting Started

Before you start working on a plugin, it's good to have a basic understanding of Python packaging and namespace packages in particular.

You can find sample plugins in the /tests/external_plugins_src/ directory of the jrnl source.

Understanding the Entry Class

Importer and exporter plugins work on the Entry class, which is responsible for representing the data in a journal entry. Plugins will generally access the following properties and functions of this class:

• title (string): a single line that represents a entry's title.
• date (datetime.datetime): the date and time assigned to an entry.
• body (string): the main body of the entry. Can be any length. jrnl assumes no particular structure here.
• starred (boolean): true if an entry is "starred"
• tags (list of strings): the tags attached to an entry. Each tag includes the pre-facing "tag symbol" which defaults to @.
• __init__(journal, date=None, text="", starred=False): constructor for new entries
  • journal (jrnl.Journal.Journal): a link to an existing Journal class. Mainly used to access its configuration.
  • date (datetime.datetime): the date of the entry
  • text (string): includes the entry's title and its body if one is included. When the title, body, or tags of an entry are requested, this text will the parsed to determine the tree.
  • starred (boolean)

!!! warning The Entry class is likely to change in future versions of journal. In particular, there may be a unique identifier added to it. Also, when using the DayOne backend, entries have additional metadata, including a "uuid" unique identifier.

Creating an Importer Plugin

An importer takes source data, turns it into Entries and then appends those entries to a Journal.

Structure

• The importer class must be named Importer, and should sub-class jrnl.plugins.base.BaseImporter.
• The importer module must be within the jrnl.contrib.importer namespace.
• The importer must not have any __init__.py files in the base directories (but you can have one for your importer base directory if it is in a directory rather than a single file).
• The importer must expose at least the following the following members:
  • version (string): the version of the plugin. Displayed to help the user debug their installations.
  • names (list of strings): these are the "names" that can be passed to the CLI to involve your importer. If you specify one used by a built-in plugin, it will overwrite it (effectively making the built-in one unavailable).
  • import_(journal, input=None): the actual importer. Must append entries to the journal passed to it. It is recommended to accept either a filename or standard input as a source.

Importer Example

You can find a basic Importer plugin in the jrnl source at /tests/external_plugins_src/jrnl/contrib/importer/simple_json.py. The sample plugin assumes that it will be provided with a nicely formatted JSON file.

!!! warning This sample code is very minimal, doesn't do any error checking, and doesn't try to import all possible entry metadata.

Use Cases

Another potential use of a custom importer is to effectively create a scripted entry creator. For example, maybe each day you want to create a journal entry that contains the answers to specific questions; you could create a custom "importer" that would ask you the questions, and then create an entry containing the answers provided.

Creating an Exporter Plugin

An exporter takes either a whole journal or a specific entry and exports it.

Structure

• The exporter class must be named Exporter and should sub-class jrnl.plugins.base.BaseExporter.
• The exporter module must be within the jrnl.contrib.exporter namespace.
• The exporter must not have any __init__.py files in the base directories (but you can have one for your exporter base directory if it is in a directory rather than a single file).
• The exporter should expose at least the following the following members (there are a few more you will need to define if you don't subclass jrnl.plugins.base.BaseExporter):
  • version (string): the version of the plugin. Displayed to help the user debug their installations.
  • names (list of strings): these are the "names" that can be passed to the CLI to invole your exporter. If you specific one used by a built-in plugin, it will overwrite it (effectively making the built-in one unavailable).
  • extension (string): the file extention used on exported entries.
  • export_entry(entry): given an entry, returns a string of the formatted, exported entry.
  • export_journal(journal): (optional) given a journal, returns a string of the formatted, exported entries of the journal. If not implemented, jrnl will call export_entry() on each entry in turn and then concatenate the results together.

Exporter Example

You can find a basic Exporter plugin in the jrnl source at /tests/external_plugins_src/jrnl/contrib/exporter/custom_json.py.

Note that a more extensive JSON exporter is included in jrnl and so this (if installed) would override the built in exporter.

!!! warning The above is very minimal, doesn't do any error checking, and doesn't export all entry metadata.

Special Exporters

There are a few "special" exporters, in that they are called by jrnl in situations other than a traditional export. They are:

• short -- called by jrnl --short. Displays each entry on a single line. The default is to print the timestamp of the entry, followed by the title. The built-in (default) plugin is at jrnl.plugins.exporter.short.
• default -- called when a different format is not specified. The built-in (default) plugin is at jrnl.plugins.exporter.pretty.

Development Tips

• Editable installs (pip install -e ...) don't seem to play nice with the namespace layout. If your plugin isn't appearing, try a non-editable install of both jrnl and your plugin.
• If you run jrnl from the main project root directory (the one that contains jrnl's source code), namespace plugins won't be recognized. This is (I suspect) because the Python interpreter will find your jrnl source directory (which doesn't contain your namespace plugins) before it find your "site-packages" directory (i.e. installed packages, which will recognize namespace packages).
• Don't name your plugin file "testing.py" or it won't be installed (at least automatically) by pip.
• For examples, you can look to the jrnl's internal importers and exporters. As well, there are some basic external examples included in jrnl's git repo at tests/external_plugins_src (including the example code above).
• Custom importers and exporters can be given the same name as a built-in importer or exporter to override it.