metrics should include their labels when printed to ease debugging (#82)

motivation: ease debugging

changes: confirm metrics types to CustomStringConvertible

Sources/CoreMetrics/Metrics.swift

@@ -84,6 +84,12 @@ public class Counter {
     }
 }
 
+extension Counter: CustomStringConvertible {
+    public var description: String {
+        return "Counter(\(self.label), dimensions: \(self.dimensions))"
+    }
+}
+
 public extension Recorder {
     /// Create a new `Recorder`.
     ///
@@ -158,6 +164,12 @@ public class Recorder {
     }
 }
 
+extension Recorder: CustomStringConvertible {
+    public var description: String {
+        return "\(type(of: self))(\(self.label), dimensions: \(self.dimensions), aggregate: \(self.aggregate))"
+    }
+}
+
 /// A gauge is a metric that represents a single numerical value that can arbitrarily go up and down.
 /// Gauges are typically used for measured values like temperatures or current memory usage, but also "counts" that can go up and down, like the number of active threads.
 /// Gauges are modeled as `Recorder` with a sample size of 1 and that does not perform any aggregation.
@@ -356,6 +368,12 @@ public class Timer {
     }
 }
 
+extension Timer: CustomStringConvertible {
+    public var description: String {
+        return "Timer(\(self.label), dimensions: \(self.dimensions))"
+    }
+}
+
 /// The `MetricsSystem` is a global facility where the default metrics backend implementation (`MetricsFactory`) can be
 /// configured. `MetricsSystem` is set up just once in a given program to set up the desired metrics backend
 /// implementation.

Tests/MetricsTests/CoreMetricsTests+XCTest.swift

@@ -43,6 +43,7 @@ extension MetricsTests {
             ("testDestroyingGauge", testDestroyingGauge),
             ("testDestroyingCounter", testDestroyingCounter),
             ("testDestroyingTimer", testDestroyingTimer),
+            ("testDescriptions", testDescriptions),
         ]
     }
 }

Tests/MetricsTests/CoreMetricsTests.swift

@@ -391,4 +391,21 @@ class MetricsTests: XCTestCase {
         let identityAgain = ObjectIdentifier(timerAgain)
         XCTAssertNotEqual(identity, identityAgain, "since the cached metric was released, the created a new should have a different identity")
     }
+
+    func testDescriptions() throws {
+        let metrics = TestMetrics()
+        MetricsSystem.bootstrapInternal(metrics)
+
+        let timer = Timer(label: "hello.timer")
+        XCTAssertEqual("\(timer)", "Timer(hello.timer, dimensions: [])")
+
+        let counter = Counter(label: "hello.counter")
+        XCTAssertEqual("\(counter)", "Counter(hello.counter, dimensions: [])")
+
+        let gauge = Gauge(label: "hello.gauge")
+        XCTAssertEqual("\(gauge)", "Gauge(hello.gauge, dimensions: [], aggregate: false)")
+
+        let recorder = Recorder(label: "hello.recorder")
+        XCTAssertEqual("\(recorder)", "Recorder(hello.recorder, dimensions: [], aggregate: true)")
+    }
 }