uro(myces)

uromyces is a toy Rust re-implementation of parts of Beancount's functionality.

How to use / run

You can use the provided Makefile to set up a virtualenv (at .venv) and install uromyces in it with make dev and then try out e.g. uro check -v $BEANCOUNT_FILE to run a bean-check like script that will do a full parse and print out any errors. There is also a uro compare command to print out differences between Beancount and uromyces.

For more elaborate playing around it's probably best to write a Python script that uses the uromyces.load_file function.

Components

Just like Beancount, this tries to go from an input file to an usable result of entries.

It does so in the following series of steps.

1. Parse single files with a tree-sitter grammar to obtain abstract syntax trees.
2. Convert the syntax tree to produce Rust data structures.
3. Combine the parsed results from multiple files and run initial validations.
4. Booking
5. Plugins
6. Validation

Performance

On my personal ledger, this is faster than Beancount as follows:

• parsing is about 2x faster
• booking is about 40x faster
• plugins for documents, implicit prices and validations each about 10x faster

Parsing

There's quite some room for improvement in the parser surely, it hasn't been the focus so far. Since the parser does more work per-file, parallelisation with rayon maybe could give nice speed-ups for users who have multiple includes. There's a couple other Rust parser implementations for Beancount already, maybe one of them could be adapted as well. With caching, the parsing performance should not be that relevant since we only need to reparse files that changed.

Imcremental computation

In the context of Fava, using salsa-rs ("A generic framework for on-demand, incrementalized computation.") seems like a good fit to speed up the incremental re-parses and more of a modified ledger.

Differences to Beancount (V3)

• Not a lot of attention has been placed on generating the same kinds of errors. So, e.g., for a transaction that does not balance, the error messages from Beancount might be quite different.
• The automatic filling of missing currencies is stricter (less powerful) than the one by Beancount and only takes the account balances into account to infer cost currencies. IMHO leaving out currencies should be discouraged and making this depend on the previous account balance seems error-prone.
• Likewise, the interpolation is less powerful. For example it won't be able to interpolate a missing total cost. Interpolating total cost seems to be rather an edge case anyway.
• The (deprecated) total cost syntax ({{}}) is not supported.
• Deprecated options are not supported.
• The options account_rounding, infer_tolerance_from_cost, and plugin_processing_mode are not supported.

Etymology

The name is derived from the genus of rust fungi that can befall bean plants.