Crate beancount_parser_lima

beancount-parser-lima

A zero-copy parser for Beancount in Rust.

It is intended to be a complete implementation of the Beancount file format, except for those parts which are deprecated and other features as documented here (in a list which may not be comprehensive).

Currently under active development. APIs are subject to change, but I hope not majorly.

The slightly strange name is because of a somewhat careless failure on my part to notice the existing beancount-parser when starting this project, for which apologies.

Features

• fast, thanks to Logos and Chumsky zero copy

• beautiful error messages, thanks to Ariadne

• interface for applications to also report beautiful errors in their original context, as in the example below

• focus on conceptual clarity of application domain objects mapped to Rust types

• Python bindings (work-in-progress)

Roadmap and Status

• create Python bindings, so that this could be a drop-in replacement for the existing Beancount parser (which is not to say it will necessarily become that!)

• improve API in the light of experience, i.e. when it gets some use 😅

• address mistakes, misunderstandings, and edge-cases in the initial implementation as they are discovered

beancount-parser-lima v0.2.1 is able to parse the example.beancount file from the official Beancount repo.

Examples

dump

This simply parses a Beancount file and outputs the results of parsing, using the Display implementations for the parser output types. The special filename STDIN causes it to read instead from standard input and parse the resulting inline string.

cargo run --example dump -- ./examples/data/full.beancount

check

This is an example of reporting errors against source locations by the application rather than the parser. This is important as semantic errors are not the business of the core parser to detect and report.

cargo run --example check -- ./examples/data/full.beancount

extract

This is more of a sanity check than anything else, that applications are able to extract parsed values without relying on the Display trait used by dump.

cargo run --example extract -- ./examples/data/full.beancount

Uncertainties / TODOs

Yeah, Beancount is complicated, and I may have made some mistakes here. Current list of uncertainties, which is certainly not comprehensive.

• metadata tags/links for a directive get folded in with those in the directive header line

Unsupported

This is an incomplete list of what is currently unsupported.

• custom directive

Unsupported Options

• allow_pipe_separator
• allow_deprecated_none_for_tags_and_links
• default_tolerance
• experiment_explicit_tolerances
• insert_pythonpath
• plugin
• tolerance
• use_legacy_fixed_tolerances

Also, unary options are not supported.

Alpha Status Dependencies

• Chumsky 1.0.0.alpha.* releases are required for zero-copy support

• smallvec 2.0.0-alpha.* releases are required for correct lifetime inference

Alternatives

beancount-parser is another parser for Beancount which predates this one, using nom instead of Chumsky.

License

Licensed under either of

• Apache License, Version 2.0 LICENSE-APACHE
• MIT license LICENSE-MIT

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Examples

This example generates the output as shown above. The supporting function parse is required in order to avoid lifetime problems.

use beancount_parser_lima::{
    BeancountParser, BeancountSources, DirectiveVariant, ParseError, ParseSuccess,
};

fn main() {
    let sources = BeancountSources::from(PathBuf::from("examples/data/error-post-balancing.beancount"));
    let parser = BeancountParser::new(&sources);

    parse(&sources, &parser, &io::stderr());
}

fn parse<W>(sources: &BeancountSources, parser: &BeancountParser, error_w: W)
where
    W: Write + Copy,
{
    match parser.parse() {
        Ok(ParseSuccess {
            directives,
            options: _,
            plugins: _,
            mut warnings,
        }) => {
            let mut errors = Vec::new();

            for directive in directives {
                if let DirectiveVariant::Transaction(transaction) = directive.variant() {
                    let mut postings = transaction.postings().collect::<Vec<_>>();
                    let n_postings = postings.len();
                    let n_amounts = itertools::partition(&mut postings, |p| p.amount().is_some());

                    if postings.is_empty() {
                        warnings.push(directive.warning("no postings"));
                    } else if n_amounts + 1 < n_postings {
                        errors.push(
                            directive
                                .error("multiple postings without amount specified")
                                .related_to_all(postings[n_amounts..].iter().copied()),
                        );
                    } else if n_amounts == n_postings {
                        let total: Decimal =
                            postings.iter().map(|p| p.amount().unwrap().value()).sum();

                        if total != Decimal::ZERO {
                            let last_amount = postings.pop().unwrap().amount().unwrap();
                            let other_amounts = postings.iter().map(|p| p.amount().unwrap());

                            errors.push(
                                last_amount
                                    .error(format!("sum is {}, expected zero", total))
                                    .related_to_all(other_amounts)
                                    .in_context(&directive),
                            )
                        }
                    }
                }
            }

            sources.write(error_w, errors).unwrap();
            sources.write(error_w, warnings).unwrap();
        }

        Err(ParseError { errors, warnings }) => {
            sources.write(error_w, errors).unwrap();
            sources.write(error_w, warnings).unwrap();
        }
    }
}

Re-exports

• pub use types::*;

Modules

• types

Structs

• BeancountParser
  The Beancount parser itself, which tokenizes and parses the source files contained in BeancountSources.
• BeancountSources
  Contains the content of the Beancount source file, and the content of the transitive closure of all the include’d source files.
• Options
  All options read in from option pragmas, excluding those for internal processing only.
• ParseError
  The value returned when parsing fails.
• ParseSuccess
  A successful parsing all the files, containing date-ordered Directives, Options, Plugins, and any Warnings.