MemorySink

`MemorySink`

Canonical source: protos/lib/logging/MemorySink.protos at locked revision e99b712ecf658a527b1fe82c8beba2c1286d8dc9.

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//! In-memory sinks that retain emitted events, mainly for tests and for
//! programs that inspect their own log output. A memory sink keeps the exact
//! emitted events: it neither copies nor formats them, and it has no capacity
//! limit, eviction, or clearing operation.

/// Answers a fresh frozen sink with no retained events.
///
/// The sink answers:
///
/// - `emit(event)`: retains `event`, which must be recognized by
///   `std:logging/LogEvent`, after every event retained before it, and answers
///   `null`. Any other argument signals an Error and retains nothing.
/// - `events()`: a fresh frozen Array of the retained events in emission order.
///   Each call answers a new Array; later emissions do not change an Array
///   already answered.
call: () => {
    LogEvent: import("std:logging/LogEvent")

    retained: []

    sink: {
        emit: (event) => {
            LogEvent.recognizes(event).ifFalse(() => {
                Error().signal()
            })
            retained = Array(...retained, event)
            null
        }

        events: () => {
            snapshot: Array(...retained)
            snapshot.freeze()
        }
    }
    sink.freeze()
}

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