Add mutating merge method to SpanAttributes (#17)

* Add mutating merge method to SpanAttributes

* Update SpanAttributes.merge documentation 📖

Co-authored-by: Konrad `ktoso` Malawski <[email protected]>

Co-authored-by: Konrad `ktoso` Malawski <[email protected]>

Author: slashmo

Sources/Tracing/Span.swift

@@ -529,6 +529,14 @@ extension SpanAttributes {
         }
     }
 
+    /// Merges the given `SpanAttributes` into these `SpanAttributes` by overwriting values of duplicate keys with those of the
+    /// `other` attributes.
+    ///
+    /// - Parameter other: `SpanAttributes` to merge.
+    public mutating func merge(_ other: SpanAttributes) {
+        self._attributes.merge(other._attributes, uniquingKeysWith: { _, rhs in rhs })
+    }
+
     /// - Returns: Number of attributes stored.
     public var count: Int {
         return self._attributes.count

Tests/TracingTests/SpanTests+XCTest.swift

@@ -35,6 +35,7 @@ extension SpanTests {
                 ("testSpanAttributesUX", testSpanAttributesUX),
                 ("testSpanAttributesCustomValue", testSpanAttributesCustomValue),
                 ("testSpanAttributesAreIterable", testSpanAttributesAreIterable),
+                ("testSpanAttributesMerge", testSpanAttributesMerge),
                 ("testSpanParentConvenience", testSpanParentConvenience),
            ]
    }

Tests/TracingTests/SpanTests.swift

@@ -137,6 +137,26 @@ final class SpanTests: XCTestCase {
         }
     }
 
+    func testSpanAttributesMerge() {
+        var attributes: SpanAttributes = [
+            "0": 0,
+            "1": true,
+            "2": "test",
+        ]
+        let other: SpanAttributes = [
+            "0": 1,
+            "1": false,
+            "3": "new",
+        ]
+
+        attributes.merge(other)
+
+        XCTAssertEqual(attributes["0"]?.toSpanAttribute(), 1)
+        XCTAssertEqual(attributes["1"]?.toSpanAttribute(), false)
+        XCTAssertEqual(attributes["2"]?.toSpanAttribute(), "test")
+        XCTAssertEqual(attributes["3"]?.toSpanAttribute(), "new")
+    }
+
     func testSpanParentConvenience() {
         var parentBaggage = Baggage.topLevel
         parentBaggage[TestBaggageContextKey.self] = "test"