support balance assertion tolerance

resolve #70

CHANGELOG.md

@@ -8,6 +8,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ## [Unreleased]
 
 
+### Added
+
+* `Balance::tolerance` field
+
+### Fixed
+
+* Accept tolerance syntax
+
+
 ## [2.0.4] - 2024-01-19
 
 ### Fixed

src/account.rs

@@ -147,6 +147,10 @@ pub struct Balance<D> {
     pub account: Account,
     /// Amount the amount should have on the date
     pub amount: Amount<D>,
+    /// Explicit precision tolerance
+    ///
+    /// See: <https://beancount.github.io/docs/precision_tolerances.html#explicit-tolerances-on-balance-assertions>
+    pub tolerance: Option<D>,
 }
 
 /// Pad directive
@@ -222,8 +226,25 @@ pub(super) fn close(input: Span<'_>) -> IResult<'_, Close> {
 pub(super) fn balance<D: Decimal>(input: Span<'_>) -> IResult<'_, Balance<D>> {
     let (input, account) = parse(input)?;
     let (input, _) = space1(input)?;
-    let (input, amount) = amount::parse(input)?;
-    Ok((input, Balance { account, amount }))
+    let (input, value) = amount::expression(input)?;
+    let (input, tolerance) = opt(preceded(space0, tolerance))(input)?;
+    let (input, _) = space1(input)?;
+    let (input, currency) = amount::currency(input)?;
+    Ok((
+        input,
+        Balance {
+            account,
+            amount: Amount { value, currency },
+            tolerance,
+        },
+    ))
+}
+
+fn tolerance<D: Decimal>(input: Span<'_>) -> IResult<'_, D> {
+    let (input, _) = char('~')(input)?;
+    let (input, _) = space0(input)?;
+    let (input, tolerance) = amount::expression(input)?;
+    Ok((input, tolerance))
 }
 
 pub(super) fn pad(input: Span<'_>) -> IResult<'_, Pad> {

src/amount.rs

@@ -104,7 +104,7 @@ pub(crate) fn parse<D: Decimal>(input: Span<'_>) -> IResult<'_, Amount<D>> {
     Ok((input, Amount { value, currency }))
 }
 
-pub(super) fn expression<D: Decimal>(input: Span<'_>) -> IResult<'_, D> {
+pub(crate) fn expression<D: Decimal>(input: Span<'_>) -> IResult<'_, D> {
     alt((negation, sum))(input)
 }
 

tests/parser_spec.rs

@@ -84,20 +84,35 @@ fn should_parse_pad_source_account(#[case] input: &str, #[case] expected: &str)
 
 #[rstest]
 #[case(
-    "2020-04-10 balance Assets:US:BofA:Checking        2473 USD",
-    2473,
-    "USD"
+    "2013-09-10 balance Assets:US:Vanguard  305.205 RGAGX",
+    305.205,
+    None,
+    "RGAGX"
+)]
+#[case(
+    "2013-09-10 balance Assets:US:Vanguard  305.205 ~ 0.002 RGAGX",
+    305.205,
+    Some(0.002),
+    "RGAGX"
+)]
+#[case(
+    "2013-09-10 balance Assets:US:Vanguard  305.205~0.002 RGAGX",
+    305.205,
+    Some(0.002),
+    "RGAGX"
 )]
 fn should_parse_balance_assertion_amount(
     #[case] input: &str,
-    #[case] expected_value: impl Into<f64>,
+    #[case] expected_value: f64,
+    #[case] expected_tolerance: Option<f64>,
     #[case] expected_currency: &str,
 ) {
     let DirectiveContent::Balance(assertion) = parse_single_directive(input).content else {
         panic!("was not an open directive");
     };
-    assert_eq!(assertion.amount.value, expected_value.into());
+    assert_eq!(assertion.amount.value, expected_value);
     assert_eq!(assertion.amount.currency.as_str(), expected_currency);
+    assert_eq!(assertion.tolerance, expected_tolerance);
 }
 
 #[rstest]