Modifies OtlpMetricExporter initializer to inject envVarHeaders; improves testability.

Author: BennettSmith

Sources/Exporters/OpenTelemetryProtocol/metric/OtlpMetricExporter.swift

@@ -17,14 +17,15 @@ public class OtlpMetricExporter: MetricExporter {
     let config : OtlpConfiguration
     var callOptions : CallOptions? = nil
 
+    
 
-
-    public init(channel: GRPCChannel, config: OtlpConfiguration = OtlpConfiguration(), logger: Logger = Logger(label: "io.grpc", factory: { _ in SwiftLogNoOpLogHandler() })) {
+    public init(channel: GRPCChannel, config: OtlpConfiguration = OtlpConfiguration(), logger: Logger = Logger(label: "io.grpc", factory: { _ in SwiftLogNoOpLogHandler() }), envVarHeaders: [(String,String)]? = EnvVarHeaders.attributes
+    ) {
         self.channel = channel
         self.config = config
         self.metricClient = Opentelemetry_Proto_Collector_Metrics_V1_MetricsServiceClient(channel: self.channel)
 
-        if let headers = EnvVarHeaders.attributes {
+        if let headers = envVarHeaders {
             callOptions = CallOptions(customMetadata: HPACKHeaders(headers), logger: logger)
         } else if let headers = config.headers {
             callOptions = CallOptions(customMetadata: HPACKHeaders(headers), logger: logger)

Tests/ExportersTests/OpenTelemetryProtocol/OtlpMetricExporterTests.swift

@@ -1,3 +1,7 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
 
 import Foundation
 import Logging
@@ -54,6 +58,24 @@ class OtlpMetricExproterTests: XCTestCase {
         XCTAssertEqual(logger.label, "my.grpc.logger")
     }
 
+    func testConfigHeadersIsNil_whenDefaultInitCalled() throws {
+        let exporter = OtlpMetricExporter(channel: channel)
+        XCTAssertNil(exporter.config.headers)
+    }
+
+    func testConfigHeadersAreSet_whenInitCalledWithCustomConfig() throws {
+        let config: OtlpConfiguration = OtlpConfiguration(timeout: TimeInterval(10), headers: [("FOO", "BAR")])
+        let exporter = OtlpMetricExporter(channel: channel, config: config)
+        XCTAssertNotNil(exporter.config.headers)
+        XCTAssertEqual(exporter.config.headers?[0].0, "FOO")
+        XCTAssertEqual(exporter.config.headers?[0].1, "BAR")
+    }
+
+    func testConfigHeadersAreSet_whenInitCalledWithExplicitHeaders() throws {
+        let exporter = OtlpMetricExporter(channel: channel, envVarHeaders: [("FOO", "BAR")])
+        XCTAssertNil(exporter.config.headers)
+        XCTAssertEqual("BAR", exporter.callOptions?.customMetadata.first(name: "FOO"))
+    }
 
     func testGaugeExport() {
         let metric = generateGaugeMetric()