[generator] Fix bug 17232 - Invalid class name generated in the Libra…

…ries.g.cs file

https://bugzilla.xamarin.com/show_bug.cgi?id=17232

* Added support for specifying library path in FieldAttribute
* Fixed generator error when Namespaces contains dots `.`
* Added error BI1042 Missing '[Field (LibraryName=value)]' for {field_pi.Name} (e.g."__Internal")
  instead of generating invalid c# code when no LibraryName is provided
  in 3rd party bindings
* Kept support for just using the system library name in FieldAttribute
  (i.e. [Field ("UnboundFooSymbol", "UIKit")]

This does not change our current generated code at all:
https://gist.github.com/dalexsoto/338464a260bc6971e7b665ca9463e8b9

src/error.cs

@@ -56,6 +56,7 @@
 //		BI1039 The selector {0} on type {1} is found multiple times with different argument length {2} : {3}.
 //		BI1040 The selector {0} on type {1} is found multiple times with different argument out states on argument {2}.
 //		BI1041 The selector {0} on type {1} is found multiple times with different argument types on argument {2} - {3} : {4}.
+//		BI1042 Missing '[Field (LibraryName=value)]' for {field_pi.Name} (e.g."__Internal")
 //	BI11xx	warnings
 //		BI1101 Trying to use a string as a [Target]
 //		BI1102 Using the deprecated EventArgs for a delegate signature in {0}.{1}, please use DelegateName instead

src/generator-enums.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Reflection;
 using XamCore.Foundation;
 using XamCore.ObjCRuntime;
@@ -96,8 +97,8 @@ void GenerateEnum (Type type)
 				library_name = library_name.Substring (ns.Prefix.Length + 1);
 
 			// there might not be any other fields in the framework
-			if (!libraries.Contains (library_name))
-				libraries.Add (library_name);
+			if (!libraries.Any (l => l.Item1 == library_name))
+				libraries.Add (new Tuple <string, string> (library_name, null));
 		}
 
 		if (error != null) {

src/generator.cs

@@ -1485,7 +1485,7 @@ public partial class Generator : IMemberGatherer {
 	Dictionary<Type,TrampolineInfo> trampolines = new Dictionary<Type,TrampolineInfo> ();
 	Dictionary<Type,int> trampolines_generic_versions = new Dictionary<Type,int> ();
 	Dictionary<Type,Type> notification_event_arg_types = new Dictionary<Type,Type> ();
-	List <string> libraries = new List <string> ();
+	List<Tuple<string, string>> libraries = new List<Tuple<string, string>> (); // <LibraryName, libraryPath>
 
 	List<Tuple<string, ParameterInfo[]>> async_result_types = new List<Tuple <string, ParameterInfo[]>> ();
 	HashSet<string> async_result_types_emitted = new HashSet<string> ();
@@ -3004,7 +3004,33 @@ void GenerateTrampolinesForQueue (TrampolineInfo [] queue)
 			print ("}} /* class {0} */", ti.NativeInvokerName);
 		}
 	}
-
+
+	// We need to check against the user using just UIKit (and friends) in the FieldAttribute
+	// so we need to reflect the libraries contained in our Constants class and do the mapping
+	// we will return the system library path if found
+	bool IsNotSystemLibrary (string library_name)
+	{
+		string library_path = null;
+		return IsNotSystemLibrary (library_name, ref library_path);
+	}
+
+	bool IsNotSystemLibrary (string library_name, ref string library_path)
+	{
+		var libSuffixedName = $"{library_name}Library";
+		var constType = typeof (
+#if XAMCORE_2_0
+		XamCore.ObjCRuntime.Constants);
+#else
+		XamCore.Constants);
+#endif
+		var field = constType.GetFields (BindingFlags.Public | BindingFlags.Static).FirstOrDefault (f => f.Name == libSuffixedName);
+		if (field == null)
+			return true;
+
+		library_path = (string) field.GetValue (null);
+		return false;
+	}
+
 	void GenerateLibraryHandles ()
 	{
 		sw = GetOutputStream ("ObjCRuntime", "Libraries");
@@ -3013,10 +3039,14 @@ void GenerateLibraryHandles ()
 		print ("namespace {0} {{", ns.CoreObjCRuntime); indent++;
 		print ("[CompilerGenerated]");
 		print ("static partial class Libraries {"); indent++;
-		foreach (string library_name in libraries.OrderBy (v => v)) {
-			print ("static public class {0} {{", library_name); indent++;
+		foreach (var library_info in libraries.OrderBy (v => v.Item1)) {
+			var library_name = library_info.Item1; // Getting the info from the tuple for readability
+			var library_path = library_info.Item2; // Getting the info from the tuple for readability
+			print ("static public class {0} {{", library_name.Replace (".", string.Empty)); indent++;
 			if (BindThirdPartyLibrary && library_name == "__Internal") {
 				print ("static public readonly IntPtr Handle = Dlfcn.dlopen (null, 0);");
+			} else if (BindThirdPartyLibrary && library_path != null && IsNotSystemLibrary (library_name)) {
+				print ($"static public readonly IntPtr Handle = Dlfcn.dlopen (\"{library_path}\", 0);");
 			} else {
 				print ("static public readonly IntPtr Handle = Dlfcn.dlopen (Constants.{0}Library, 0);", library_name);
 			}
@@ -6228,6 +6258,7 @@ public void Generate (Type type)
 				foreach (var field_pi in field_exports.OrderBy (f => f.Name)) {
 					var fieldAttr = (FieldAttribute) field_pi.GetCustomAttributes (typeof (FieldAttribute), true) [0];
 					string library_name; 
+					string library_path = null;
 
 					if (fieldAttr.LibraryName != null){
 						// Remapped
@@ -6241,19 +6272,35 @@ public void Generate (Type type)
 								library_name = CoreServicesMap;
 								break;
 							}
-						} 
+						} else {
+							// we get something in LibraryName from FieldAttribute so we asume
+							// it is a path to a library, so we save the path and change library name
+							// to a valid identifier if needed
+							library_path = library_name;
+							if (library_name.Contains ("/")) {
+								var lastSlashIdx = library_name.LastIndexOf ("/");
+								library_name = library_name.Substring (lastSlashIdx + 1);
+							}
+							if (library_name.Contains ("."))
+								library_name = library_name.Replace (".", string.Empty);
+						}
+					} else if (BindThirdPartyLibrary) {
+						// User should provide a LibraryName
+						throw new BindingException (1042, true, $"Missing '[Field (LibraryName=value)]' for {field_pi.Name} (e.g.\"__Internal\")");
 					} else {
 						library_name = type.Namespace;
 						// note: not every binding namespace will start with ns.Prefix (e.g. MonoTouch.)
-						if (!String.IsNullOrEmpty (ns.Prefix) && library_name.StartsWith (ns.Prefix))
+						if (!String.IsNullOrEmpty (ns.Prefix) && library_name.StartsWith (ns.Prefix)) {
 							library_name = library_name.Substring (ns.Prefix.Length + 1);
+							library_name = library_name.Replace (".", string.Empty); // Remove dots from namespaces
+						}
 					}
 
-					if (!libraries.Contains (library_name)) {
-						libraries.Add (library_name);
+					if (!libraries.Any (l => l.Item1 == library_name)) {
+						libraries.Add (new Tuple<string, string> (library_name, library_path));
 					}
 					bool is_unified_internal = field_pi.IsUnifiedInternal ();
-					
+
 					string fieldTypeName = FormatType (field_pi.DeclaringType, field_pi.PropertyType);
 					// Value types we dont cache for now, to avoid Nullable<T>
 					if (!field_pi.PropertyType.IsValueType) {
@@ -6263,7 +6310,7 @@ public void Generate (Type type)
 					}
 
 					PrintPreserveAttribute (field_pi);
-					print ("[Field (\"{0}\",  \"{1}\")]", fieldAttr.SymbolName, library_name);
+					print ("[Field (\"{0}\",  \"{1}\")]", fieldAttr.SymbolName, library_path ?? library_name);
 					PrintPlatformAttributes (field_pi);
 					if (Generator.HasAttribute (field_pi, typeof (AdvancedAttribute))){
 						print ("[EditorBrowsable (EditorBrowsableState.Advanced)]");