Fix add, introduce isEmpty (#42)

* Add isEmpty, fix add()

isEmpty

* New tests + organization

* Warnings

* precondition -> assert

* PR feedback

Author: ladd

Sources/NautilusTelemetry/Exporters/Exporter+Metrics.swift

@@ -59,7 +59,7 @@ extension Exporter {
 			let startTimeUnixNano = convertToOTLP(time: counter.startTime)
 
 			let doubleValue: Double? = asDouble(value)
-			var intValueString: String? = asIntString(value)
+			let intValueString: String? = asIntString(value)
 
 			let timeUnixNano = convertToOTLP(time: ContinuousClock.now)
 
@@ -107,7 +107,7 @@ extension Exporter {
 			let startTimeUnixNano = convertToOTLP(time: counter.startTime)
 
 			let doubleValue: Double? = asDouble(value)
-			var intValueString: String? = asIntString(value)
+			let intValueString: String? = asIntString(value)
 
 			let timeUnixNano = convertToOTLP(time: ContinuousClock.now)
 
@@ -155,7 +155,7 @@ extension Exporter {
 			let startTimeUnixNano = convertToOTLP(time: counter.startTime)
 
 			let doubleValue: Double? = asDouble(value)
-			var intValueString: String? = asIntString(value)
+			let intValueString: String? = asIntString(value)
 
 			let timeUnixNano = convertToOTLP(time: ContinuousClock.now)
 
@@ -203,7 +203,7 @@ extension Exporter {
 			let startTimeUnixNano = convertToOTLP(time: gauge.startTime)
 
 			let doubleValue: Double? = asDouble(value)
-			var intValueString: String? = asIntString(value)
+			let intValueString: String? = asIntString(value)
 
 			let timeUnixNano = convertToOTLP(time: ContinuousClock.now)
 

…utilusTelemetry/ResourceAttributes.swift …Instrumentation/ResourceAttributes.swiftSources/NautilusTelemetry/ResourceAttributes.swift renamed to Sources/NautilusTelemetry/Instrumentation/ResourceAttributes.swift Sources/NautilusTelemetry/ResourceAttributes.swift renamed to Sources/NautilusTelemetry/Instrumentation/ResourceAttributes.swift

@@ -29,8 +29,14 @@ public class Counter<T: MetricNumeric>: Instrument, ExportableInstrument {
 
 	public var isMonotonic: Bool { true }
 
+	public var isEmpty: Bool { lock.withLock { values.isEmpty } }
+
 	public func add(_ number: T, attributes: TelemetryAttributes = [:]) {
-		precondition(number >= 0, "counters can only be increased")
+		if isMonotonic, number < 0 {
+			// UpDownCounter is not monotonic
+			assert(false, "monotonic counters can only be increased")
+			return
+		}
 		lock.withLockUnchecked {
 			values.add(number, attributes: attributes)
 		}

Sources/NautilusTelemetry/Metrics/Counter.swift

@@ -34,8 +34,14 @@ public class Histogram<T: MetricNumeric>: Instrument, ExportableInstrument {
 	public private(set) var endTime: ContinuousClock.Instant? = nil
 	public var aggregationTemporality = AggregationTemporality.delta
 
+	public var isEmpty: Bool { lock.withLock { values.isEmpty } }
+
 	public func record(_ number: T, attributes: TelemetryAttributes = [:]) {
-		precondition(number >= 0, "counters can only be increased")
+		if number < 0 {
+			assert(false, "histograms can only be increased")
+			return
+		}
+
 		lock.withLockUnchecked {
 			values.record(number, attributes: attributes)
 		}

Sources/NautilusTelemetry/Metrics/Histogram.swift

@@ -26,6 +26,10 @@ struct HistogramBuckets<T: MetricNumeric> {
 	var data: [UInt64]
 	let explicitBounds: [T]
 
+	var isEmpty: Bool {
+		return data.isEmpty || data.allSatisfy { $0 == 0 }
+	}
+
 	mutating func record(_ number: T) {
 		sum += number
 		count += 1
@@ -42,6 +46,7 @@ struct HistogramBuckets<T: MetricNumeric> {
 		// In the range of (lastBound...infinity).
 		data[count] += 1
 	}
+
 }
 
 // MARK: - HistogramValues
@@ -64,6 +69,10 @@ struct HistogramValues<T: MetricNumeric> {
 
 	var values = [TelemetryAttributes: HistogramBuckets<T>]()
 
+	var isEmpty: Bool {
+		values.isEmpty || values.values.allSatisfy { $0.isEmpty }
+	}
+
 	mutating func record(_ number: T, attributes: TelemetryAttributes = [:]) {
 		var value = values[attributes] ?? HistogramBuckets<T>(explicitBounds: explicitBounds)
 		value.record(number)
@@ -81,4 +90,5 @@ struct HistogramValues<T: MetricNumeric> {
 
 		return copy
 	}
+
 }

Sources/NautilusTelemetry/Metrics/HistogramValues.swift

@@ -36,6 +36,8 @@ public protocol Instrument: AnyObject {
 	/// This model assumes delta mode metrics.
 	/// TBD: figure out aggregation model: https://opentelemetry.io/docs/specs/otel/metrics/data-model/#sums-delta-to-cumulative
 	func snapshotAndReset() -> Instrument
+
+	var isEmpty: Bool { get }
 }
 
 // MARK: - ExportableInstrument

Sources/NautilusTelemetry/Metrics/Instrument.swift

@@ -12,8 +12,12 @@ struct MetricValues<T: MetricNumeric> {
 
 	var values = [TelemetryAttributes: T]()
 
+	var isEmpty: Bool {
+		values.isEmpty || values.values.allSatisfy { $0 == 0 }
+	}
+
 	mutating func add(_ number: T, attributes: TelemetryAttributes = [:]) {
-		var metricValue = values[attributes] ?? number
+		var metricValue = values[attributes] ?? 0
 		metricValue += number
 		values[attributes] = metricValue
 	}

Sources/NautilusTelemetry/Metrics/MetricValues.swift

@@ -30,6 +30,8 @@ public class ObservableCounter<T: MetricNumeric>: Instrument, ExportableInstrume
 
 	public var isMonotonic: Bool { true }
 
+	public var isEmpty: Bool { lock.withLock { values.isEmpty } }
+
 	/// https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/api.md#asynchronous-counter-creation
 	public func observe(_ number: T, attributes: TelemetryAttributes = [:]) {
 		lock.withLockUnchecked {

Sources/NautilusTelemetry/Metrics/ObservableCounter.swift

@@ -28,6 +28,8 @@ public class ObservableGauge<T: MetricNumeric>: Instrument, ExportableInstrument
 	public private(set) var endTime: ContinuousClock.Instant? = nil
 	public let aggregationTemporality = AggregationTemporality.unspecified
 
+	public var isEmpty: Bool { false }
+
 	public func observe(_ number: T, attributes: TelemetryAttributes = [:]) {
 		lock.withLockUnchecked {
 			values.set(number, attributes: attributes)

Sources/NautilusTelemetry/Metrics/ObservableGauge.swift

@@ -30,6 +30,8 @@ public class ObservableUpDownCounter<T: MetricNumeric>: Instrument, ExportableIn
 
 	public var isMonotonic: Bool { false }
 
+	public var isEmpty: Bool { lock.withLock { values.isEmpty } }
+
 	public func observe(_ number: T, attributes: TelemetryAttributes = [:]) {
 		lock.withLockUnchecked {
 			values.set(number, attributes: attributes)