Struct ImplicitPricesPlugin 

pub struct ImplicitPricesPlugin;

Plugin that generates price entries from transaction postings.

For each posting with a @/@@ price annotation or a {...} cost spec, generates a corresponding Price directive. Mirrors Python beancount’s beancount.plugins.implicit_prices.

Per-posting price math is delegated to rustledger_core::extract_per_unit_price — the same helper used by the BQL query path. Pre-fix (issue #992) this plugin had its own implementation that emitted @@ total amounts as per-unit prices (off by a factor of units) AND emitted both an annotation-derived AND a cost-derived price for postings that had both. Both bugs disappear once the helper is the single source of truth.

Augment-vs-reduce gating: Python’s plugin uses Inventory.add_position and skips emitting the cost-derived price when the posting matched as MatchResult.REDUCED (a sell against an existing lot). Without that check, sells written as -N CCY {} — which booking later resolves to a specific lot’s cost — produce a phantom price entry per match. We mirror that here by tracking per-account positions keyed on (account, units.currency, cost-fingerprint) and treating a posting as REDUCED when the running quantity for its key has the opposite sign. Price annotations (@/@@) still emit unconditionally even on reducing postings — Python’s from_price branch fires before the REDUCED check too. Without this gate rledger over-emitted ~4 prices per reducing-sell-with-{} posting on fixtures like fava-portfolio- returns (closes the residual ~5 over-emit cases left behind by #1048).

Pipeline assumption: this plugin operates on post-booking directives. Postings that would cross zero (e.g. a -150 sell against a +100 lot) have already been split by the booker into two postings — one fully-reducing leg against the existing lot and one augmenting/creating leg for the residual. Our inline inventory update sees them sequentially and correctly classifies the residual leg as not-REDUCED. If the plugin is ever moved earlier in the pipeline, the gate would over-suppress on pre-split crossing postings.

Lots with a cost spec that carries neither number_per nor number_total (e.g. bare {2024-01-01}) aren’t tracked in the inventory — cost_fingerprint returns None and the posting passes through the cost-emit branch directly. Python’s Inventory.add_amount would still track these, but since the cost-derived emit path also requires a number, the tracker participation doesn’t change emit decisions.

Trait Implementations

impl NativePlugin for ImplicitPricesPlugin

fn name(&self) -> &'static str

Plugin name.

fn description(&self) -> &'static str

Plugin description.

fn process(&self, input: PluginInput) -> PluginOutput

Process directives and return modified directives + errors.

fn is_synth(&self) -> bool

Whether this plugin synthesizes directives the loader’s Phase::Early validation depends on (e.g. injecting Open directives so account-presence checks see them).