[generator] enum map.csv can set @deprecated-since for enum values (#1070)

Context: dotnet/android#7670

While auditing the `Mono.Android.dll`, we've found that some constants
were added to the wrong enums.

Consider [`xamarin-android/src/Mono.Android/map.csv`][0],
lines 739-743:

	E,28,android/app/usage/UsageStatsManager.STANDBY_BUCKET_ACTIVE,10,Android.App.Usage.StandbyBucket,Active,remove,
	E,28,android/app/usage/UsageStatsManager.STANDBY_BUCKET_FREQUENT,30,Android.App.Usage.StandbyBucket,Frequent,remove,
	E,28,android/app/usage/UsageStatsManager.STANDBY_BUCKET_RARE,40,Android.App.Usage.StandbyBucket,Rare,remove,
	E,30,android/app/usage/UsageStatsManager.STANDBY_BUCKET_RESTRICTED,45,Android.App.Usage.UsageStatsInterval,Restricted,remove,
	E,28,android/app/usage/UsageStatsManager.STANDBY_BUCKET_WORKING_SET,20,Android.App.Usage.StandbyBucket,WorkingSet,remove,


`STANDBY_BUCKET_RESTRICTED` should have been added to `StandbyBucket`
instead of `UsageStatsInterval`.

To fix this in a backwards-compatible way, we can add it to both enums:

	E,30,android/app/usage/UsageStatsManager.STANDBY_BUCKET_RESTRICTED,45,Android.App.Usage.StandbyBucket,Restricted,remove,
	A,30,,45,Android.App.Usage.UsageStatsInterval,Restricted,remove,

However, we have no way to mark `UsageStatsInterval.Restricted` as
`[Obsolete]`, so people may still unintentionally use it.

Add a new field to our csv that allows us to set a constant's
`@deprecated-since` field, the `30` at the end:

	A,30,,45,Android.App.Usage.UsageStatsInterval,Restricted,remove,,30

This allows us to generate:

	[global::System.Runtime.Versioning.ObsoletedOSPlatform ("android30.0")]
	Restricted = 45

Additionally, when the cause is that we accidentally added an invalid
value to the enum, we should provide a better obsolete message, letting
the user know that the value will not function.  This is done by
setting `@deprecated-since` to `-1`:

	A,30,,45,Android.App.Usage.UsageStatsInterval,Restricted,remove,,-1

resulting in:

	[global::System.Obsolete (@"This value was incorrectly added to the enumeration and is not a valid value")]
	Restricted = 45

[0]: https://github.com/xamarin/xamarin-android/blob/cc70ce20aff6934532a8cb6a7bddbf3710fd7e1c/src/Mono.Android/map.csv

Author: jpobst

Documentation/EnumMappingFile.md

@@ -65,7 +65,7 @@ There is now a "v2" version of defining constants. This is a line-level change
 and you can mix "v1" and "v2" lines in the same file for backwards compatibility, 
 but for consistency it's probably better to stick to one style.
 
-A "v2" line contains up to 8 fields:
+A "v2" line contains up to 9 fields:
 
 * **Action** - The action to perform. This is what denotes a "v2" line, if the first
   character is not one of the following it will be treated as "v1".
@@ -89,10 +89,14 @@ A "v2" line contains up to 8 fields:
   * `keep` - Keeps the Java constant
 * **Flags** - If this field contains `flags` the enum will be created with the
   `[Flags]` attribute. (Any member will `flags` will make the whole enum `[Flags]`.)
-
+* **Deprecated Since** - This is generally only used by `Mono.Android.dll` to denote
+  the Android level the constant was deprecated in. Specifying "-1" will add an obsolete
+  message to the effect of: "This value was incorrectly added to the enumeration and is 
+  not a valid value". Leave blank if constant is not deprecated.
+  
 Full example:
 ```
-E,10,android/view/Window.PROGRESS_START,0,Android.Views.WindowProgress,Start,remove,flags
+E,10,android/view/Window.PROGRESS_START,0,Android.Views.WindowProgress,Start,remove,flags,30
 ```
 
 [0]: https://docs.microsoft.com/en-us/xamarin/android/platform/binding-java-library/customizing-bindings/java-bindings-metadata#enumfieldsxml-and-enummethodsxml

src/Java.Interop.Tools.Generator/Enumification/ConstantEntry.cs

@@ -16,6 +16,7 @@ public class ConstantEntry
 		public string? EnumMember { get; set; }
 		public FieldAction FieldAction { get; set; }
 		public bool IsFlags { get; set; }
+		public int? DeprecatedSince { get; set; }
 
 		public string EnumNamespace {
 			get {
@@ -133,7 +134,8 @@ static ConstantEntry FromVersion2String (CsvParser parser)
 				EnumFullType = parser.GetField (4),
 				EnumMember = parser.GetField (5),
 				FieldAction = FromFieldActionString (parser.GetField (6)),
-				IsFlags = parser.GetField (7).ToLowerInvariant () == "flags"
+				IsFlags = parser.GetField (7).ToLowerInvariant () == "flags",
+				DeprecatedSince = parser.GetFieldAsNullableInt32 (8)
 			};
 
 			entry.NormalizeJavaSignature ();
@@ -175,7 +177,8 @@ public string ToVersion2String ()
 				EnumFullType,
 				EnumMember,
 				ToConstantFieldActionString (FieldAction),
-				IsFlags ? "flags" : string.Empty
+				IsFlags ? "flags" : string.Empty,
+				DeprecatedSince.HasValue ? DeprecatedSince.Value.ToString () : string.Empty,
 			};
 
 			return string.Join (",", fields);

src/Java.Interop.Tools.Generator/Enumification/ConstantsParser.cs

@@ -48,6 +48,20 @@ public static void SaveEnumMapCsv (List<ConstantEntry> constants, string filenam
 
 		public static void SaveEnumMapCsv (List<ConstantEntry> constants, TextWriter writer)
 		{
+			var column_names = new [] {
+				"Action",
+				"API Level",
+				"JNI Signature",
+				"Enum Value",
+				"C# Enum Type",
+				"C# Member Name",
+				"Field Action",
+				"Is Flags",
+				"Deprecated Since",
+			};
+
+			writer.WriteLine ("// " + string.Join (",", column_names));
+
 			foreach (var c in Sort (constants))
 				writer.WriteLine (c.ToVersion2String ());
 		}

src/Java.Interop.Tools.Generator/Utilities/CsvParser.cs

@@ -23,5 +23,15 @@ public int GetFieldAsInt (int index)
 		{
 			return int.Parse (GetField (index));
 		}
+
+		public int? GetFieldAsNullableInt32 (int index)
+		{
+			var value = GetField (index);
+
+			if (int.TryParse (value, out var val))
+				return val;
+
+			return default;
+		}
 	}
 }

tests/Java.Interop.Tools.Generator-Tests/Enumification/ConstantEntryTests.cs

@@ -84,6 +84,7 @@ public void ParseEnumMapV2 ()
 			Assert.AreEqual ("Cdsect", entry.EnumMember);
 			Assert.AreEqual (FieldAction.Keep, entry.FieldAction);
 			Assert.False (entry.IsFlags);
+			Assert.IsNull (entry.DeprecatedSince);
 		}
 
 		[Test]
@@ -99,13 +100,14 @@ public void ParseAddEnumMapV2 ()
 			Assert.AreEqual ("Org.XmlPull.V1.XmlPullParserNode", entry.EnumFullType);
 			Assert.AreEqual ("Cdsect", entry.EnumMember);
 			Assert.AreEqual (FieldAction.None, entry.FieldAction);
+			Assert.IsNull (entry.DeprecatedSince);
 			Assert.False (entry.IsFlags);
 		}
 
 		[Test]
 		public void ParseRemoveEnumMapV2 ()
 		{
-			var csv = "R,10,I:org/xmlpull/v1/XmlPullParser.CDSECT,5,,,remove";
+			var csv = "R,10,I:org/xmlpull/v1/XmlPullParser.CDSECT,5,,,remove,,33";
 			var entry = ConstantEntry.FromString (csv);
 
 			Assert.AreEqual (ConstantAction.Remove, entry.Action);
@@ -116,6 +118,7 @@ public void ParseRemoveEnumMapV2 ()
 			Assert.AreEqual (string.Empty, entry.EnumMember);
 			Assert.AreEqual (FieldAction.Remove, entry.FieldAction);
 			Assert.False (entry.IsFlags);
+			Assert.AreEqual (33, entry.DeprecatedSince.Value);
 		}
 	}
 }

tests/generator-Tests/Unit-Tests/EnumGeneratorTests.cs

@@ -133,6 +133,60 @@ public void ObsoleteFieldButNotEnumAttributeSupport ()
 			Assert.False (writer.ToString ().NormalizeLineEndings ().Contains ("[global::System.Obsolete(@\"deprecated\")]WithExcluded=1"), writer.ToString ());
 		}
 
+		[Test]
+		public void ObsoletedOSPlatformAttributeOverrideSupport ()
+		{
+			var xml = @"<api>
+			  <package name='java.lang' jni-name='java/lang'>
+			    <class abstract='false' deprecated='not deprecated' final='false' name='Object' static='false' visibility='public' jni-signature='Ljava/lang/Object;' />
+			  </package>
+			  <package name='android.app' jni-name='android/app'>
+			    <class abstract='false' deprecated='not deprecated' extends='java.lang.Object' extends-generic-aware='java.lang.Object' jni-extends='Ljava/lang/Object;' final='false' name='ActivityManager' static='false' visibility='public' jni-signature='Landroid/app/ActivityManager;'>
+			      <field deprecated='not deprecated' final='true' name='RECENT_IGNORE_UNAVAILABLE' jni-signature='Ljava/lang/String;' static='true' transient='false' type='java.lang.String' type-generic-aware='java.lang.String' value='&quot;android.permission.BIND_CHOOSER_TARGET_SERVICE&quot;' visibility='public' volatile='false' api-since='30' />
+			    </class>
+			  </package>
+			</api>";
+
+			options.UseObsoletedOSPlatformAttributes = true;
+
+			var enu = CreateEnum ();
+			enu.Value.Members.Single (m => m.EnumMember == "WithExcluded").DeprecatedSince = 33;
+
+			var gens = ParseApiDefinition (xml);
+
+			generator.WriteEnumeration (options, enu, gens.ToArray ());
+
+			// The field itself is not deprecated, but [ObsoletedOSPlatform] should be written because we set `DeprecatedSince` on the enum map
+			Assert.True (writer.ToString ().NormalizeLineEndings ().Contains ("[global::System.Runtime.Versioning.ObsoletedOSPlatform(\"android33.0\")]WithExcluded=1"), writer.ToString ());
+		}
+
+		[Test]
+		public void ObsoleteAccidentalAddition ()
+		{
+			var xml = @"<api>
+			  <package name='java.lang' jni-name='java/lang'>
+			    <class abstract='false' deprecated='not deprecated' final='false' name='Object' static='false' visibility='public' jni-signature='Ljava/lang/Object;' />
+			  </package>
+			  <package name='android.app' jni-name='android/app'>
+			    <class abstract='false' deprecated='not deprecated' extends='java.lang.Object' extends-generic-aware='java.lang.Object' jni-extends='Ljava/lang/Object;' final='false' name='ActivityManager' static='false' visibility='public' jni-signature='Landroid/app/ActivityManager;'>
+			      <field deprecated='not deprecated' final='true' name='RECENT_IGNORE_UNAVAILABLE' jni-signature='Ljava/lang/String;' static='true' transient='false' type='java.lang.String' type-generic-aware='java.lang.String' value='&quot;android.permission.BIND_CHOOSER_TARGET_SERVICE&quot;' visibility='public' volatile='false' api-since='30' />
+			    </class>
+			  </package>
+			</api>";
+
+			options.UseObsoletedOSPlatformAttributes = true;
+
+			var enu = CreateEnum ();
+			enu.Value.Members.Single (m => m.EnumMember == "WithExcluded").DeprecatedSince = -1;
+
+			var gens = ParseApiDefinition (xml);
+
+			generator.WriteEnumeration (options, enu, gens.ToArray ());
+
+			// "-1" is a "magic" API level which adds a message indicating the enum value shouldn't even exist
+			Assert.True (writer.ToString ().NormalizeLineEndings ().Contains ("[global::System.Obsolete(@\"Thisvaluewasincorrectlyaddedtotheenumerationandisnotavalidvalue\")]WithExcluded=1"), writer.ToString ());
+		}
+
 		protected new string GetExpected (string testName)
 		{
 			var root = Path.GetDirectoryName (Assembly.GetExecutingAssembly ().Location);

tools/generator/Java.Interop.Tools.Generator.CodeGeneration/EnumGenerator.cs

@@ -59,11 +59,16 @@ EnumWriter CreateWriter (CodeGenerationOptions opt, KeyValuePair<string, EnumDes
 
 				SourceWriterExtensions.AddSupportedOSPlatform (m.Attributes, member.ApiLevel, opt);
 
-				// Some of our source fields may have been marked with:
-				// "This constant will be removed in the future version. Use XXX enum directly instead of this field."
-				// We don't want this message to propogate to the enum.
-				if (managedMember != null && managedMember.Value.Field?.DeprecatedComment?.Contains ("enum directly instead of this field") == false)
+				if (member.DeprecatedSince.HasValue) {
+					// If we've manually marked it as obsolete in map.csv, that takes precedence
+					var msg = member.DeprecatedSince.Value == -1 ? "This value was incorrectly added to the enumeration and is not a valid value" : "deprecated";
+					SourceWriterExtensions.AddObsolete (m.Attributes, msg, opt, deprecatedSince: member.DeprecatedSince);
+				} else if (managedMember != null && managedMember.Value.Field?.DeprecatedComment?.Contains ("enum directly instead of this field") == false) {
+					// Some of our source fields may have been marked with:
+					// "This constant will be removed in the future version. Use XXX enum directly instead of this field."
+					// We don't want this message to propogate to the enum.
 					SourceWriterExtensions.AddObsolete (m.Attributes, managedMember.Value.Field.DeprecatedComment, opt, deprecatedSince: managedMember.Value.Field.DeprecatedSince);
+				}
 
 				enoom.Members.Add (m);
 			}