new: FQMetricDescriptor overload option

Adds a new way to create metrics using an FQMetricDescriptor, which makes it easier to build metric names programmatically. The changes are fully backward compatible.

Signed-off-by: Melissa Kilby <[email protected]>

Author: incertum

Sources/Prometheus/MetricDescriptor.swift

@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the SwiftPrometheus open source project
+//
+// Copyright (c) 2018-2025 SwiftPrometheus project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of SwiftPrometheus project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+/// Creates a new ``FQMetricDescriptor`` that defines the components of a fully qualified Prometheus metric name.
+///
+/// The final, underscore-separated metric name is generated by the ``name`` computed property. The ``helpText``
+/// is used to generate the corresponding `# HELP` line in the Prometheus exposition format.
+///
+/// - Warning: This initializer will trigger a `preconditionFailure` if ``metricName`` is an empty string.
+///
+/// - Parameter namespace: An optional top-level namespace for the metric.
+/// - Parameter subsystem: An optional subsystem to group related metrics within a namespace.
+/// - Parameter metricName: The required, descriptive base name of the metric.
+/// - Parameter unitName: An optional suffix describing the metric's unit (e.g., `_seconds`, `_total`).
+/// - Parameter helpText: Optional descriptive text for the metric.
+/// - Returns: A new ``FQMetricDescriptor`` instance with the specified components.
+public struct FQMetricDescriptor {
+    public let namespace: String?
+    public let subsystem: String?
+    public let metricName: String
+    public let unitName: String?
+    public let helpText: String?
+
+    public init(
+        namespace: String? = nil,
+        subsystem: String? = nil,
+        metricName: String,
+        unitName: String? = nil,
+        helpText: String? = nil
+    ) {
+        precondition(!metricName.isEmpty, "metricName must not be empty")
+        self.namespace = namespace
+        self.subsystem = subsystem
+        self.metricName = metricName
+        self.unitName = unitName
+        self.helpText = helpText
+    }
+
+    public var name: String {
+        [namespace, subsystem, metricName, unitName]
+            .compactMap { $0?.isEmpty == false ? $0 : nil }
+            .joined(separator: "_")
+    }
+}

Sources/Prometheus/PrometheusCollectorRegistry.swift

@@ -93,6 +93,18 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``Counter`` collector or returns the already existing one with the same name,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``Counter`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Returns: A ``Counter`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeCounter(descriptor: FQMetricDescriptor) -> Counter {
+        return self.makeCounter(name: descriptor.name)
+    }
+
     /// Creates a new ``Counter`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -150,6 +162,20 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``Counter`` collector or returns the already existing one with the same name,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``Counter`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Parameter labels: Labels are sets of key-value pairs that allow us to characterize and organize
+    ///                     what’s actually being measured in a Prometheus metric.
+    /// - Returns: A ``Counter`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeCounter(descriptor: FQMetricDescriptor, labels: [(String, String)]) -> Counter {
+        return self.makeCounter(name: descriptor.name, labels: labels)
+    }
+
     /// Creates a new ``Gauge`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -178,6 +204,18 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``Gauge`` collector or returns the already existing one with the same name,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``Gauge`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Returns: A ``Gauge`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeGauge(descriptor: FQMetricDescriptor) -> Gauge {
+        return self.makeGauge(name: descriptor.name)
+    }
+
     /// Creates a new ``Gauge`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -235,6 +273,20 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``Gauge`` collector or returns the already existing one with the same name and labels,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``Gauge`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Parameter labels: Labels are sets of key-value pairs that allow us to characterize and organize
+    ///                     what’s actually being measured in a Prometheus metric.
+    /// - Returns: A ``Gauge`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeGauge(descriptor: FQMetricDescriptor, labels: [(String, String)]) -> Gauge {
+        return self.makeGauge(name: descriptor.name, labels: labels)
+    }
+
     /// Creates a new ``DurationHistogram`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -264,6 +316,19 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``DurationHistogram`` collector or returns the already existing one with the same name,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``DurationHistogram`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Parameter buckets: Define the buckets that shall be used within the ``DurationHistogram``
+    /// - Returns: A ``DurationHistogram`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeDurationHistogram(descriptor: FQMetricDescriptor, buckets: [Duration]) -> DurationHistogram {
+        return self.makeDurationHistogram(name: descriptor.name, buckets: buckets)
+    }
+
     /// Creates a new ``DurationHistogram`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -338,6 +403,25 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``DurationHistogram`` collector or returns the already existing one with the same name and labels,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``DurationHistogram`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Parameter labels: Labels are sets of key-value pairs that allow us to characterize and organize
+    ///                     what’s actually being measured in a Prometheus metric.
+    /// - Parameter buckets: Define the buckets that shall be used within the ``DurationHistogram``
+    /// - Returns: A ``DurationHistogram`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeDurationHistogram(
+        descriptor: FQMetricDescriptor,
+        labels: [(String, String)],
+        buckets: [Duration]
+    ) -> DurationHistogram {
+        return self.makeDurationHistogram(name: descriptor.name, labels: labels, buckets: buckets)
+    }
+
     /// Creates a new ``ValueHistogram`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -362,6 +446,19 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``ValueHistogram`` collector or returns the already existing one with the same name,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``ValueHistogram`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Parameter buckets: Define the buckets that shall be used within the ``ValueHistogram``
+    /// - Returns: A ``ValueHistogram`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeValueHistogram(descriptor: FQMetricDescriptor, buckets: [Double]) -> ValueHistogram {
+        return self.makeValueHistogram(name: descriptor.name, buckets: buckets)
+    }
+
     /// Creates a new ``ValueHistogram`` collector or returns the already existing one with the same name.
     ///
     /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
@@ -408,6 +505,27 @@ public final class PrometheusCollectorRegistry: Sendable {
         }
     }
 
+    /// Creates a new ``ValueHistogram`` collector or returns the already existing one with the same name and labels,
+    /// based on the provided descriptor.
+    ///
+    /// When the ``PrometheusCollectorRegistry/emit(into:)`` is called, metrics from the
+    /// created ``ValueHistogram`` will be part of the export.
+    ///
+    /// - Parameter descriptor: An ``FQMetricDescriptor`` that provides the fully qualified name for the metric.
+    /// - Parameter labels: Labels are sets of key-value pairs that allow us to characterize and organize
+    ///                     what’s actually being measured in a Prometheus metric.
+    /// - Parameter buckets: Define the buckets that shall be used within the ``ValueHistogram``
+    /// - Returns: A ``ValueHistogram`` that is registered with this ``PrometheusCollectorRegistry``
+    public func makeValueHistogram(
+        descriptor: FQMetricDescriptor,
+        labels: [(String, String)],
+        buckets: [Double]
+    ) -> ValueHistogram {
+        return self.makeValueHistogram(name: descriptor.name, labels: labels, buckets: buckets)
+    }
+
+    // MARK: - Histogram
+
     // MARK: Destroying Metrics
 
     /// Unregisters a ``Counter`` from the ``PrometheusCollectorRegistry``. This means that the provided ``Counter``