restructure for linux file path testing

src/OpenTelemetry.ResourceDetectors.Host/HostDetector.cs

@@ -5,7 +5,6 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
-using System.Runtime.CompilerServices;
 using System.Text;
 using Microsoft.Win32;
 using OpenTelemetry.Resources;
@@ -17,7 +16,10 @@ namespace OpenTelemetry.ResourceDetectors.Host;
 /// </summary>
 public sealed class HostDetector : IResourceDetector
 {
+    private const string ETC_MACHINEID = "/etc/machine-id";
+    private const string ETC_VAR_DBUS_MACHINEID = "/var/lib/dbus/machine-id";
     private readonly PlatformID platformId;
+    private readonly Func<IEnumerable<string>> getFilePaths;
     private readonly Func<string> getMacOsMachineId;
     private readonly Func<string> getWindowsMachineId;
 
@@ -27,6 +29,7 @@ public sealed class HostDetector : IResourceDetector
     public HostDetector()
         : this(
         Environment.OSVersion.Platform,
+        GetFilePaths,
         GetMachineIdMacOs,
         GetMachineIdWindows)
     {
@@ -38,9 +41,10 @@ public HostDetector()
     /// <param name="platformId">Target platform ID.</param>
     /// <param name="getMacOsMachineId">Function to get MacOS machine ID.</param>
     /// <param name="getWindowsMachineId">Function to get Windows machine ID.</param>
-    internal HostDetector(PlatformID platformId, Func<string> getMacOsMachineId, Func<string> getWindowsMachineId)
+    internal HostDetector(PlatformID platformId, Func<IEnumerable<string>> getFilePaths, Func<string> getMacOsMachineId, Func<string> getWindowsMachineId)
     {
         this.platformId = platformId;
+        this.getFilePaths = getFilePaths ?? throw new ArgumentNullException(nameof(getFilePaths));
         this.getMacOsMachineId = getMacOsMachineId ?? throw new ArgumentNullException(nameof(getMacOsMachineId));
         this.getWindowsMachineId = getWindowsMachineId ?? throw new ArgumentNullException(nameof(getWindowsMachineId));
     }
@@ -68,6 +72,12 @@ public Resource Detect()
         return Resource.Empty;
     }
 
+    private static IEnumerable<string> GetFilePaths()
+    {
+        yield return ETC_MACHINEID;
+        yield return ETC_VAR_DBUS_MACHINEID;
+    }
+
     private static string GetMachineIdMacOs()
     {
         var startInfo = new ProcessStartInfo
@@ -108,7 +118,7 @@ private string GetMachineId()
 
     private string GetMachineIdLinux()
     {
-        var paths = new[] { "/etc/machine-id", "/var/lib/dbus/machine-id" };
+        var paths = this.getFilePaths();
 
         foreach (var path in paths)
         {

test/OpenTelemetry.ResourceDetectors.Host.Tests/HostDetectorTests.cs

@@ -2,7 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0
 
 using System;
-using System.IO;
+using System.Collections;
+using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using OpenTelemetry.Resources;
@@ -12,6 +13,9 @@ namespace OpenTelemetry.ResourceDetectors.Host.Tests;
 
 public class HostDetectorTests
 {
+    private static readonly IEnumerable<string> ETC_MACHINEID = new[] { "Samples/etc_machineid" };
+    private static readonly IEnumerable<string> ETC_VAR_DBUS_MACHINEID = new[] { "Samples/etc_var_dbus_machineid" };
+
     [Fact]
     public void TestHostAttributes()
     {
@@ -26,22 +30,43 @@ public void TestHostAttributes()
     }
 
     [Fact]
-    public void TestHostMachineId()
+    public void TestHostMachineIdLinux()
     {
-        var etcMachineIdStream = (string path) =>
+        var combos = new[]
         {
-            return path == "/etc/machine-id"
-                ? new MemoryStream(Encoding.UTF8.GetBytes("etc-machine-id"))
-                : null;
+            (Enumerable.Empty<string>(), string.Empty),
+            (ETC_MACHINEID, "etc_machineid"),
+            (ETC_VAR_DBUS_MACHINEID, "etc_var_dbus_machineid"),
+            (Enumerable.Concat(ETC_MACHINEID, ETC_VAR_DBUS_MACHINEID), "etc_machineid"),
         };
-        var varLibDbusMachineIdStream = new MemoryStream(Encoding.UTF8.GetBytes("var-lib-dbus-machine-id"));
+
+        foreach (var (path, expected) in combos)
+        {
+            var detector = new HostDetector(
+                PlatformID.Unix,
+                () => path,
+                () => throw new Exception("should not be called"),
+                () => throw new Exception("should not be called"));
+            var resource = ResourceBuilder.CreateEmpty().AddDetector(detector).Build();
+            var resourceAttributes = resource.Attributes.ToDictionary(x => x.Key, x => (string)x.Value);
+
+            if (string.IsNullOrEmpty(expected))
+            {
+                Assert.Empty(resourceAttributes[HostSemanticConventions.AttributeHostId]);
+            } else
+            {
+                Assert.NotEmpty(resourceAttributes[HostSemanticConventions.AttributeHostId]);
+                Assert.Equal(expected, resourceAttributes[HostSemanticConventions.AttributeHostId]);
+            }
+        }
     }
 
     [Fact]
     public void TestHostMachineIdMacOs()
     {
         var detector = new HostDetector(
             PlatformID.MacOSX,
+            () => Enumerable.Empty<string>(),
             () => "macos-machine-id",
             () => throw new Exception("should not be called"));
         var resource = ResourceBuilder.CreateEmpty().AddDetector(detector).Build();
@@ -55,6 +80,7 @@ public void TestHostMachineIdWindows()
     {
         var detector = new HostDetector(
             PlatformID.Win32NT,
+            () => Enumerable.Empty<string>(),
             () => throw new Exception("should not be called"),
             () => "windows-machine-id");
         var resource = ResourceBuilder.CreateEmpty().AddDetector(detector).Build();

test/OpenTelemetry.ResourceDetectors.Host.Tests/OpenTelemetry.ResourceDetectors.Host.Tests.csproj

@@ -11,4 +11,13 @@
     <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.ResourceDetectors.Host\OpenTelemetry.ResourceDetectors.Host.csproj" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Update="Samples\etc_machineid">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="Samples\etc_var_dbus_machineid">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
 </Project>

test/OpenTelemetry.ResourceDetectors.Host.Tests/Samples/etc_machineid

@@ -0,0 +1 @@
+etc_machineid

test/OpenTelemetry.ResourceDetectors.Host.Tests/Samples/etc_var_dbus_machineid

@@ -0,0 +1 @@
+etc_var_dbus_machineid