warning and error codes

Author: jonathanpeppers

Documentation/guides/messages/xa4304.md

@@ -1,4 +1,4 @@
-# Compiler Error XA4304
+# Compiler Warning XA4304
 
 The `Proguard` MSBuild task encountered a proguard configuration file
 that was not found on disk. These files are generally declared in your

Documentation/guides/messages/xa4305.md

@@ -0,0 +1,21 @@
+# Compiler Error/Warning XA4305
+
+The `CreateMultiDexMainDexClassList`, `CompileToDalvik` or `R8`
+MSBuild task encountered a `multidex.keep` file that was not found on
+disk. You can customize `multidex` settings for your Xamarin.Android
+application by adding files with the `MultiDexMainDexList` build item,
+which are combined into a final `multidex.keep` file.
+
+To learn more about `multidex` and how it relates to Android
+development, see the [Android documentation][android].
+
+## Resolution
+
+Verify you are not declaring a `MultiDexMainDexList` build item that
+does not exist.
+
+Consider submitting a [bug][bug] if you are getting this error/warning
+under normal circumstances.
+
+[android]: https://developer.android.com/studio/build/multidex
+[bug]: https://github.com/xamarin/xamarin-android/wiki/Submitting-Bugs,-Feature-Requests,-and-Pull-Requests

src/Xamarin.Android.Build.Tasks/Tasks/CompileToDalvik.cs

@@ -116,8 +116,14 @@ protected override string GenerateCommandLineCommands ()
 			cmd.AppendSwitchIfNotNull ("--input-list=", inputListFile);
 
 			if (MultiDexEnabled) {
-				cmd.AppendSwitch ("--multi-dex");
-				cmd.AppendSwitchIfNotNull ("--main-dex-list=", MultiDexMainDexListFile);
+				if (string.IsNullOrEmpty (MultiDexMainDexListFile)) {
+					Log.LogCodedWarning ("XA4305", $"MultiDex is enabled, but '{nameof (MultiDexMainDexListFile)}' was not specified.");
+				} else if (!File.Exists (MultiDexMainDexListFile)) {
+					Log.LogCodedWarning ("XA4305", MultiDexMainDexListFile, 0, $"MultiDex is enabled, but main dex list file '{MultiDexMainDexListFile}' does not exist.");
+				} else {
+					cmd.AppendSwitch ("--multi-dex");
+					cmd.AppendSwitchIfNotNull ("--main-dex-list=", MultiDexMainDexListFile);
+				}
 			}
 			cmd.AppendSwitchIfNotNull ("--output ", Path.GetDirectoryName (ClassesOutputDirectory));
 

src/Xamarin.Android.Build.Tasks/Tasks/CreateMultiDexMainDexClassList.cs

@@ -47,9 +47,16 @@ public override bool Execute ()
 			Log.LogDebugMessage ("  ProguardJarPath: {0}", ProguardJarPath);
 			Log.LogDebugMessage ("  ProguardInputJarFilter: {0}", ProguardInputJarFilter);
 
-			if (CustomMainDexListFiles != null && CustomMainDexListFiles.Any ()) {
-				var content = string.Concat (CustomMainDexListFiles.Select (i => File.ReadAllText (i.ItemSpec)));
-				File.WriteAllText (MultiDexMainDexListFile, content);
+			if (CustomMainDexListFiles?.Length > 0) {
+				var content = new List<string> ();
+				foreach (var file in CustomMainDexListFiles) {
+					if (File.Exists (file.ItemSpec)) {
+						content.Add (File.ReadAllText (file.ItemSpec));
+					} else {
+						Log.LogCodedError ("XA4305", file.ItemSpec, 0, $"'MultiDexMainDexList' file '{file.ItemSpec}' does not exist.");
+					}
+				}
+				File.WriteAllText (MultiDexMainDexListFile, string.Concat (content));
 				return true;
 			}
 

src/Xamarin.Android.Build.Tasks/Tasks/R8.cs

@@ -95,16 +95,19 @@ protected override string GenerateCommandLineCommands ()
 					if (File.Exists (file))
 						cmd.AppendSwitchIfNotNull ("--pg-conf ", file);
 					else
-						Log.LogWarning ("Proguard configuration file '{0}' was not found.", file);
+						Log.LogCodedWarning ("XA4304", file, 0, "Proguard configuration file '{0}' was not found.", file);
 				}
 				cmd.AppendSwitchIfNotNull ("--pg-map-output ", ProguardMappingOutput);
+			}
 
-				// multidexing
-				if (EnableMultiDex) {
-					if (!string.IsNullOrWhiteSpace (MultiDexMainDexListFile) && File.Exists (MultiDexMainDexListFile))
-						cmd.AppendSwitchIfNotNull ("--main-dex-list ", MultiDexMainDexListFile);
-					else
-						Log.LogWarning ($"MultiDex is enabled, but main dex list file '{MultiDexMainDexListFile}' does not exist.");
+			// multidexing
+			if (EnableMultiDex) {
+				if (string.IsNullOrEmpty (MultiDexMainDexListFile)) {
+					Log.LogCodedWarning ("XA4305", $"MultiDex is enabled, but '{nameof (MultiDexMainDexListFile)}' was not specified.");
+				} else if (!File.Exists (MultiDexMainDexListFile)) {
+					Log.LogCodedWarning ("XA4305", MultiDexMainDexListFile, 0, $"MultiDex is enabled, but main dex list file '{MultiDexMainDexListFile}' does not exist.");
+				} else {
+					cmd.AppendSwitchIfNotNull ("--main-dex-list ", MultiDexMainDexListFile);
 				}
 			}