notcoal - notmuch filters, not made from (char)coal

notcoal provides both a library as well as a standalone binary. The latter can be used as an "initial tagging" system, the former may be integrated into a bigger e-mail client making use of notmuch-rs.

What?

Takes regex rules from a JSON file and if any match, either adds new tags, removes tags or runs an arbitrary binaries for further processing. Rules support AND as well as OR operations.

Example

[{
    "name": "money",
    "desc": "Money stuff",
    "rules": [
        {"from": "@(real\\.bank|gig-economy\\.career)",
         "subject": ["report", "month" ]},
        {"from": "no-reply@trusted\\.bank",
         "subject": "statement"}
    ],
    "op": {
        "add": "€£$",
        "rm": ["inbox", "unread"],
        "run": ["any-binary-in-our-path-or-absolute-path", "--argument"]
    }
}]

Here the matching expands to:

( from: ("@real.bank" OR "@gig-economy.career") AND subject: ("report" AND "month") )
OR
( from: "no-reply@trusted.bank" AND subject: "statement" )

If if this filter is applied the operations will

• add the tag €£$
• remove the tags inbox and unread
• run the equivalent of /bin/sh -c 'any-binary-in-our-path-or-absolute-path --argument' with 3 additional environment variables:

NOTCOAL_FILTER_NAME=money
NOTCOAL_FILE_NAME=/path/to/maildir/new/filename
NOTCOAL_MSG_ID=e81cadebe7dab1cc6fac7e6a41@some-isp

Filters aren't only restricted to matching from and subject headers (all of which are treated case-insensitive) but may try to match arbitrary headers.

Additionally there are the special match fields:

• @path: matches on the full path of a message
• @tags: matches on tags already set by previous filters
• @thread-tags: matches on tags already present in the message's thread
• @attachment: matches on an attachment name
• @attachment-body: matches on every text/plain attachment's body
• @body: matches on the messages body

The default notcoal::filter function loops through messages and then tests/applies filters in the order they have been defined in. Hence, any tag one wants to match on has to have been set by a previous matching rule.

Standalone use for "initial tagging"

To install the standalone helper binary, the simplest way is:

cargo install --locked notcoal --features=standalone

notcoal will use the same default database as notmuch itself, and the default location for the rules file is in $notmuchdb/.notmuch/hooks/notcoal-rules.json. It also expects all newly added messages (that are to be filtered) to have the new tag. To make sure that's being set, edit your .notmuch-config to include:

[new]
tags=unread;inbox;new;

Additionally, notcoal will respect the config file's maildir synchronize setting.

See notcoal --help for supplying alternative values.

If you're fine with the defaults, you can symlink $notmuchdb/.notmuch/hooks/post-new to the notcoal binary.

Thanks

vhdirk for notmuch-rs, which made this crate possible in the first place, korrat for a patch for more sensible database discovery, antifuchs' gmail-britta for inspiring the name, and Recurse Center, for creating a supportive environment 💟