OSDescription.Linux: return a user-friendly name based on /etc/os-release. (#83976)

* OSDescription.Linux: return a user-friendly name based on /etc/os-release.

* Use FileCleanupTestBase.

* Avoid some allocations by using Span.

* expectedName can be null.

* Apply suggestions from code review

Co-authored-by: Stephen Toub <[email protected]>

* Break when we encounter PRETTY_NAME.

---------

Co-authored-by: Stephen Toub <[email protected]>

Author: tmds

src/libraries/Common/src/Interop/Linux/os-release/Interop.OSReleaseFile.cs

@@ -0,0 +1,83 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.IO;
+
+internal static partial class Interop
+{
+    // Parse information from '/etc/os-release'.
+    internal static class OSReleaseFile
+    {
+        private const string EtcOsReleasePath = "/etc/os-release";
+
+        /// <summary>
+        /// Returns a user-friendly distribution name.
+        /// </summary>
+        internal static string? GetPrettyName(string filename = EtcOsReleasePath)
+        {
+            if (File.Exists(filename))
+            {
+                string[] lines;
+                try
+                {
+                    lines = File.ReadAllLines(filename);
+                }
+                catch
+                {
+                    return null;
+                }
+
+                // Parse the NAME, PRETTY_NAME, and VERSION fields.
+                // These fields are suitable for presentation to the user.
+                ReadOnlySpan<char> prettyName = default, name = default, version = default;
+                foreach (string line in lines)
+                {
+                    ReadOnlySpan<char> lineSpan = line.AsSpan();
+
+                    _ = TryGetFieldValue(lineSpan, "PRETTY_NAME=", ref prettyName) ||
+                        TryGetFieldValue(lineSpan, "NAME=", ref name) ||
+                        TryGetFieldValue(lineSpan, "VERSION=", ref version);
+
+                    // Prefer "PRETTY_NAME".
+                    if (!prettyName.IsEmpty)
+                    {
+                        return new string(prettyName);
+                    }
+                }
+
+                // Fall back to "NAME[ VERSION]".
+                if (!name.IsEmpty)
+                {
+                    if (!version.IsEmpty)
+                    {
+                        return string.Concat(name, " ", version);
+                    }
+                    return new string(name);
+                }
+
+                static bool TryGetFieldValue(ReadOnlySpan<char> line, ReadOnlySpan<char> prefix, ref ReadOnlySpan<char> value)
+                {
+                    if (!line.StartsWith(prefix))
+                    {
+                        return false;
+                    }
+                    ReadOnlySpan<char> fieldValue = line.Slice(prefix.Length);
+
+                    // Remove enclosing quotes.
+                    if (fieldValue.Length >= 2 &&
+                        fieldValue[0] is '"' or '\'' &&
+                        fieldValue[0] == fieldValue[^1])
+                    {
+                        fieldValue = fieldValue[1..^1];
+                    }
+
+                    value = fieldValue;
+                    return true;
+                }
+            }
+
+            return null;
+        }
+    }
+}

src/libraries/Common/tests/Common.Tests.csproj

@@ -16,6 +16,8 @@
              Link="Common\Interop\Linux\procfs\Interop.ProcFsStat.cs" />
     <Compile Include="$(CommonPath)Interop\Linux\procfs\Interop.ProcFsStat.TryReadStatusFile.cs"
              Link="Common\Interop\Linux\Interop.ProcFsStat.TryReadStatusFile.cs" />
+    <Compile Include="$(CommonPath)Interop\Linux\os-release\Interop.OSReleaseFile.cs"
+             Link="Common\Interop\Linux\os-release\Interop.OSReleaseFile.cs" />
     <Compile Include="$(CommonPath)System\CharArrayHelpers.cs"
              Link="Common\System\CharArrayHelpers.cs" />
     <Compile Include="$(CommonPath)System\StringExtensions.cs"
@@ -78,6 +80,7 @@
              Link="System\PasteArguments.cs" />
     <Compile Include="Tests\Interop\cgroupsTests.cs" />
     <Compile Include="Tests\Interop\procfsTests.cs" />
+    <Compile Include="Tests\Interop\OSReleaseTests.cs" />
     <Compile Include="Tests\System\IO\PathInternal.Tests.cs" />
     <Compile Include="Tests\System\IO\StringParserTests.cs" />
     <Compile Include="Tests\System\Net\HttpDateParserTests.cs" />

src/libraries/Common/tests/Tests/Interop/OSReleaseTests.cs

@@ -0,0 +1,61 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.IO;
+using System.Text;
+using Xunit;
+
+namespace Common.Tests
+{
+    public class OSReleaseTests : FileCleanupTestBase
+    {
+        [Theory]
+        // Double quotes:
+        [InlineData("NAME=\"Fedora\"\nVERSION=\"37\"\nPRETTY_NAME=\"Fedora Linux 37\"", "Fedora Linux 37")]
+        [InlineData("NAME=\"Fedora\"\nVERSION=\"37\"", "Fedora 37")]
+        [InlineData("NAME=\"Fedora\"", "Fedora")]
+        // Single quotes:
+        [InlineData("NAME='Ubuntu'\nVERSION='22.04'\nPRETTY_NAME='Ubuntu Linux 22.04'", "Ubuntu Linux 22.04")]
+        [InlineData("NAME='Ubuntu'\nVERSION='22.04'", "Ubuntu 22.04")]
+        [InlineData("NAME='Ubuntu'", "Ubuntu")]
+        // No quotes:
+        [InlineData("NAME=Alpine\nVERSION=3.14\nPRETTY_NAME=Alpine_Linux_3.14", "Alpine_Linux_3.14")]
+        [InlineData("NAME=Alpine\nVERSION=3.14", "Alpine 3.14")]
+        [InlineData("NAME=Alpine", "Alpine")]
+        // No pretty name fields:
+        [InlineData("ID=fedora\nVERSION_ID=37", null)]
+        [InlineData("", null)]
+        public void GetPrettyName_Success(
+            string content,
+            string? expectedName)
+        {
+            string path = GetTestFilePath();
+            File.WriteAllText(path, content);
+
+            string? name = Interop.OSReleaseFile.GetPrettyName(path);
+            Assert.Equal(expectedName, name);
+        }
+
+        [Fact]
+        public void GetPrettyName_NoFile_ReturnsNull()
+        {
+            string path = Path.GetRandomFileName();
+            Assert.False(File.Exists(path));
+
+            string? name = Interop.OSReleaseFile.GetPrettyName(path);
+            Assert.Null(name);
+        }
+
+        [Fact, PlatformSpecific(TestPlatforms.Linux)]
+        public void GetPrettyName_CannotRead_ReturnsNull()
+        {
+            string path = CreateTestFile();
+            File.SetUnixFileMode(path, UnixFileMode.None);
+            Assert.ThrowsAny<Exception>(() => File.ReadAllText(path));
+
+            string? name = Interop.OSReleaseFile.GetPrettyName(path);
+            Assert.Null(name);
+        }
+    }
+}

src/libraries/Common/tests/Tests/Interop/procfsTests.cs

@@ -7,7 +7,7 @@
 
 namespace Common.Tests
 {
-    public class procfsTests
+    public class procfsTests : FileCleanupTestBase
     {
         [Theory]
         [InlineData("1 (systemd) S 0 1 1 0 -1 4194560 11536 2160404 55 593 70 169 4213 1622 20 0 1 0 4 189767680 1491 18446744073709551615 1 1 0 0 0 0 671173123 4096 1260 0 0 0 17 4 0 0 25 0 0 0 0 0 0 0 0 0 0", 1, "systemd", 'S', 1, 70, 169, 0, 4, 189767680, 1491, 18446744073709551615)]
@@ -33,33 +33,29 @@ public class procfsTests
         [InlineData("5955 (a(((b) S 1806 5955 5955 34823 5955 4194304 1426 5872 0 3 16 3 16 4 20 0 1 0 674762 32677888 1447 18446744073709551615 4194304 5192652 140725672538992 140725672534152 140236068968880 0 0 3670020 1266777851 1 0 0 17 4 0 0 0 0 0 7290352 7326856 21204992 140725672540419 140725672540424 140725672540424 140725672542190 0", 5955, "a(((b", 'S', 5955, 16, 3, 0, 674762, 32677888, 1447, 18446744073709551615)]
         [InlineData("5955 (a)( ) b (() () S 1806 5955 5955 34823 5955 4194304 1426 5872 0 3 16 3 16 4 20 0 1 0 674762 32677888 1447 18446744073709551615 4194304 5192652 140725672538992 140725672534152 140236068968880 0 0 3670020 1266777851 1 0 0 17 4 0 0 0 0 0 7290352 7326856 21204992 140725672540419 140725672540424 140725672540424 140725672542190 0", 5955, "a)( ) b (() (", 'S', 5955, 16, 3, 0, 674762, 32677888, 1447, 18446744073709551615)]
         [InlineData("5955 (has\\backslash) S 1806 5955 5955 34823 5955 4194304 1426 5872 0 3 16 3 16 4 20 0 1 0 674762 32677888 1447 18446744073709551615 4194304 5192652 140725672538992 140725672534152 140236068968880 0 0 3670020 1266777851 1 0 0 17 4 0 0 0 0 0 7290352 7326856 21204992 140725672540419 140725672540424 140725672540424 140725672542190 0", 5955, "has\\backslash", 'S', 5955, 16, 3, 0, 674762, 32677888, 1447, 18446744073709551615)]
-        public static void ParseValidStatFiles_Success(
+        public void ParseValidStatFiles_Success(
             string statFileText,
             int expectedPid, string expectedComm, char expectedState, int expectedSession,
             ulong expectedUtime, ulong expectedStime, long expectedNice, ulong expectedStarttime,
             ulong expectedVsize, long expectedRss, ulong expectedRsslim)
         {
-            string path = Path.GetTempFileName();
-            try
-            {
-                File.WriteAllText(path, statFileText);
+            string path = GetTestFilePath();
+            File.WriteAllText(path, statFileText);
 
-                Interop.procfs.ParsedStat result;
-                Assert.True(Interop.procfs.TryParseStatFile(path, out result));
+            Interop.procfs.ParsedStat result;
+            Assert.True(Interop.procfs.TryParseStatFile(path, out result));
 
-                Assert.Equal(expectedPid, result.pid);
-                Assert.Equal(expectedComm, result.comm);
-                Assert.Equal(expectedState, result.state);
-                Assert.Equal(expectedSession, result.session);
-                Assert.Equal(expectedUtime, result.utime);
-                Assert.Equal(expectedStime, result.stime);
-                Assert.Equal(expectedNice, result.nice);
-                Assert.Equal(expectedStarttime, result.starttime);
-                Assert.Equal(expectedVsize, result.vsize);
-                Assert.Equal(expectedRss, result.rss);
-                Assert.Equal(expectedRsslim, result.rsslim);
-            }
-            finally { File.Delete(path); }
+            Assert.Equal(expectedPid, result.pid);
+            Assert.Equal(expectedComm, result.comm);
+            Assert.Equal(expectedState, result.state);
+            Assert.Equal(expectedSession, result.session);
+            Assert.Equal(expectedUtime, result.utime);
+            Assert.Equal(expectedStime, result.stime);
+            Assert.Equal(expectedNice, result.nice);
+            Assert.Equal(expectedStarttime, result.starttime);
+            Assert.Equal(expectedVsize, result.vsize);
+            Assert.Equal(expectedRss, result.rss);
+            Assert.Equal(expectedRsslim, result.rsslim);
         }
     }
 }

src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems

@@ -2386,6 +2386,7 @@
     <Compile Include="$(CommonPath)System\IO\StringParser.cs" Condition="'$(TargetsLinux)' == 'true'" Link="Common\System\IO\StringParser.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\Interop.libproc.GetProcessInfoById.cs" Condition="'$(TargetsOSX)' == 'true' or '$(TargetsMacCatalyst)' == 'true'" Link="Common\Interop\OSX\Interop.libproc.GetProcessInfoById.cs" />
     <Compile Include="$(CommonPath)Interop\SunOS\procfs\Interop.ProcFsStat.TryReadProcessStatusInfo.cs" Condition="'$(Targetsillumos)' == 'true' or '$(TargetsSolaris)' == 'true'" Link="Common\Interop\SunOS\Interop.ProcFsStat.TryReadProcessStatusInfo.cs" />
+    <Compile Include="$(CommonPath)Interop\Linux\os-release\Interop.OSReleaseFile.cs" Condition="'$(TargetsBrowser)' != 'true' and '$(TargetsWasi)' != 'true'" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Environment.Unix.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Environment.FreeBSD.cs" Condition="'$(TargetsFreeBSD)' == 'true'" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Environment.Linux.cs" Condition="'$(TargetsLinux)' == 'true'" />

src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeInformation.Unix.cs

@@ -10,7 +10,7 @@ public static partial class RuntimeInformation
         private static string? s_osDescription;
         private static volatile int s_osArchPlusOne;
 
-        public static string OSDescription => s_osDescription ??= Interop.Sys.GetUnixVersion();
+        public static string OSDescription => s_osDescription ??= (GetPrettyOSDescription() ?? Interop.Sys.GetUnixVersion());
 
         public static Architecture OSArchitecture
         {
@@ -30,5 +30,15 @@ public static Architecture OSArchitecture
                 return (Architecture)osArch;
             }
         }
+
+        private static string? GetPrettyOSDescription()
+        {
+            if (OperatingSystem.IsLinux())
+            {
+                return Interop.OSReleaseFile.GetPrettyName();
+            }
+
+            return null;
+        }
     }
 }

src/libraries/System.Runtime.InteropServices.RuntimeInformation/tests/DescriptionNameTests.cs

@@ -201,7 +201,14 @@ public void VerifyWindowsName()
         [Fact, PlatformSpecific(TestPlatforms.Linux)]  // Checks Linux name in RuntimeInformation
         public void VerifyLinuxName()
         {
-            Assert.Contains("linux", RuntimeInformation.OSDescription, StringComparison.OrdinalIgnoreCase);
+            if (File.Exists("/etc/os-release"))
+            {
+                Assert.Equal(Interop.OSReleaseFile.GetPrettyName("/etc/os-release"), RuntimeInformation.OSDescription);
+            }
+            else
+            {
+                Assert.Contains("linux", RuntimeInformation.OSDescription, StringComparison.OrdinalIgnoreCase);
+            }
         }
 
         [Fact, PlatformSpecific(TestPlatforms.NetBSD)]  // Checks NetBSD name in RuntimeInformation

src/libraries/System.Runtime.InteropServices.RuntimeInformation/tests/System.Runtime.InteropServices.RuntimeInformation.Tests.csproj

@@ -10,5 +10,7 @@
     <Compile Include="DescriptionNameTests.cs" />
     <Compile Include="$(CommonPath)Interop\Linux\cgroups\Interop.cgroups.cs"
              Link="Common\Interop\Linux\Interop.cgroups.cs" />
+    <Compile Include="$(CommonPath)Interop\Linux\os-release\Interop.OSReleaseFile.cs"
+             Link="Interop\Linux\os-release\Interop.OSReleaseFile.cs" />
   </ItemGroup>
 </Project>