[Linux] Properly detect Debian bookworm/sid (dotnet#6221)

The current Debian unstable distribution (codenamed "bookworm") no
longer contains any release version information in the `/etc/os-release`
file (the `VERSION` and `VERSION_ID` and `VERSION_CODENAME` fields were
removed) causing `xaprepare` to fail when running on this version of
Debian.

Fix the Debian/unstable version detection by looking for known release
codenames and faking the version number.

build-tools/xaprepare/xaprepare/ConfigAndData/Dependencies/Linux.Debian.cs

@@ -22,6 +22,11 @@ class LinuxDebian : LinuxDebianCommon
 			new DebianLinuxProgram ("zulu-8"),
 		};
 
+		static readonly Dictionary<string, string> DebianUnstableVersionMap = new Dictionary<string, string> (StringComparer.OrdinalIgnoreCase) {
+			{ "bookworm", "12" },
+			{ "bookworm/sid", "12" },
+		};
+
 		protected Version DebianRelease { get; private set; } = new Version (0, 0);
 		protected bool IsTesting { get; private set; }
 
@@ -42,24 +47,49 @@ protected override void InitializeDependencies ()
 				Dependencies.AddRange (packagesPre10);
 		}
 
-		static bool IsDebian10OrNewer (string[] lines)
+		static bool IsDebian10OrNewer (string? version)
 		{
-			if (lines == null || lines.Length < 1)
-				return false;
-
-			string version = lines[0].Trim ();
-			if (String.IsNullOrEmpty (version))
+			if (String.IsNullOrEmpty (version)) {
 				return false;
+			}
 
 			return
 				version.IndexOf ("bullseye", StringComparison.OrdinalIgnoreCase) >= 0 ||
+				version.IndexOf ("bookworm", StringComparison.OrdinalIgnoreCase) >= 0 ||
 				version.IndexOf ("sid", StringComparison.OrdinalIgnoreCase) >= 0;
 		}
 
-		protected override bool InitOS ()
+		static string? ReadDebianVersion ()
+		{
+			if (!File.Exists (DebianVersionPath)) {
+				return null;
+			}
+
+			string[] lines = File.ReadAllLines (DebianVersionPath);
+			return lines[0].Trim ();
+		}
+
+		static bool IsBookwormSidOrNewer (string? debian_version)
 		{
-			if (!base.InitOS ())
+			if (String.IsNullOrEmpty (debian_version)) {
 				return false;
+			}
+
+			return debian_version!.IndexOf ("bookworm", StringComparison.OrdinalIgnoreCase) >= 0;
+		}
+
+		protected override bool EnsureVersionInformation (Context context)
+		{
+			string? debian_version = null;
+			if (String.IsNullOrEmpty (Release)) {
+				// Debian/unstable "bookworm" (to become Debian 12 eventually) removed
+				// VERSION_ID and VERSION_CODENAME from /etc/os-release, so we need to
+				// fake it
+				debian_version = ReadDebianVersion ();
+				if (IsBookwormSidOrNewer (debian_version) && DebianUnstableVersionMap.TryGetValue (debian_version!, out string unstable_version)) {
+					Release = unstable_version;
+				};
+			}
 
 			Version debianRelease;
 			if (!Version.TryParse (Release, out debianRelease)) {
@@ -76,7 +106,11 @@ protected override bool InitOS ()
 			}
 
 			if (debianRelease.Major < 10 && DerivativeDistro && File.Exists (DebianVersionPath)) {
-				if (IsDebian10OrNewer (File.ReadAllLines (DebianVersionPath)))
+				if (String.IsNullOrEmpty (debian_version)) {
+					debian_version = ReadDebianVersion ();
+				}
+
+				if (IsDebian10OrNewer (debian_version))
 				    debianRelease = new Version (10, 0); // faking it, but it's ok
 			}
 

build-tools/xaprepare/xaprepare/ConfigAndData/Dependencies/Linux.Ubuntu.cs

@@ -38,7 +38,7 @@ protected override void InitializeDependencies ()
 			}
 		}
 
-		protected override bool InitOS ()
+		protected override bool EnsureVersionInformation (Context context)
 		{
 			Version ubuntuRelease;
 			if (!Version.TryParse (Release, out ubuntuRelease)) {
@@ -51,7 +51,7 @@ protected override bool InitOS ()
 			}
 			UbuntuRelease = ubuntuRelease;
 
-			return base.InitOS ();
+			return true;
 		}
 	};
 }

build-tools/xaprepare/xaprepare/OperatingSystems/Linux.cs

@@ -172,6 +172,11 @@ static bool MapDistro (string id, ref string distro)
 			return true;
 		}
 
+		protected virtual bool EnsureVersionInformation (Context context)
+		{
+			return true;
+		}
+
 		public static Linux DetectAndCreate (Context context)
 		{
 			string name = String.Empty;
@@ -234,6 +239,10 @@ public static Linux DetectAndCreate (Context context)
 			linux.codeName = codeName;
 			linux.derived = usingBaseDistro;
 
+			if (!linux.EnsureVersionInformation (context)) {
+				throw new InvalidOperationException ("Unable to detect version of your Linux distribution");
+			}
+
 			return linux;
 		}