Support feature settings on descriptor files

docs/error-codes.md

@@ -7,11 +7,11 @@ error and warning codes.
 
 ## Error Codes
 
-#### `IL1001`: Failed to process XML substitution: 'XML document location'. Feature 'feature' does not specify a "featurevalue" attribute
+#### `IL1001`: Failed to process 'XML document location'. Feature 'feature' does not specify a "featurevalue" attribute
 
 - The substitution in 'XML document location' with feature value 'feature' does not use the `featurevalue` attribute. These attributes have to be used together.
 
-#### `IL1002`: Failed to process XML substitution: 'XML document location'. Unsupported non-boolean feature definition 'feature'
+#### `IL1002`: Failed to process 'XML document location'. Unsupported non-boolean feature definition 'feature'
 
 - The substitution in 'XML document location' with feature value 'feature' sets the attribute `featurevalue` to a non-boolean value. Only boolean values are supported for this attribute.
 

src/linker/Linker.Steps/BodySubstituterStep.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using System.Linq;
 using System.Globalization;
 using System.Xml.XPath;
@@ -41,28 +42,7 @@ protected override void Process ()
 			ReadSubstitutions (_document);
 		}
 
-		bool ShouldProcessSubstitutions (XPathNavigator nav)
-		{
-			var feature = GetAttribute (nav, "feature");
-			if (string.IsNullOrEmpty (feature))
-				return true;
-
-			var value = GetAttribute (nav, "featurevalue");
-			if (string.IsNullOrEmpty (value)) {
-				Context.LogError ($"Failed to process XML substitution: '{_xmlDocumentLocation}'. Feature {feature} does not specify a 'featurevalue' attribute", 1001);
-				return false;
-			}
-
-			if (!bool.TryParse (value, out bool bValue)) {
-				Context.LogError ($"Failed to process XML substitution: '{_xmlDocumentLocation}'. Unsupported non-boolean feature definition {feature}", 1002);
-				return false;
-			}
-
-			if (Context.FeatureSettings == null || !Context.FeatureSettings.TryGetValue (feature, out bool featureSetting))
-				return false;
-
-			return bValue == featureSetting;
-		}
+		bool ShouldProcessSubstitutions (XPathNavigator nav) => ResolveFromXmlStep.ShouldProcessElement (nav, Context, _xmlDocumentLocation);
 
 		void ReadSubstitutions (XPathDocument document)
 		{
@@ -126,10 +106,9 @@ void ProcessTypes (AssemblyDefinition assembly, XPathNodeIterator iterator)
 
 		void ProcessType (TypeDefinition type, XPathNavigator nav)
 		{
-			if (!nav.HasChildren)
-				return;
+			Debug.Assert (ShouldProcessSubstitutions (nav));
 
-			if (!ShouldProcessSubstitutions (nav))
+			if (!nav.HasChildren)
 				return;
 
 			XPathNodeIterator methods = nav.SelectChildren ("method", "");

src/linker/Linker.Steps/LinkAttributesStep.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -154,7 +155,7 @@ void ProcessAssemblies (LinkContext context, XPathNodeIterator iterator)
 		{
 			while (iterator.MoveNext ()) {
 				if (!ShouldProcessElement (iterator.Current))
-					return;
+					continue;
 
 				if (GetFullName (iterator.Current) == "*") {
 					foreach (AssemblyDefinition assemblyIterator in context.GetAssemblies ()) {
@@ -249,6 +250,8 @@ void ProcessTypePattern (string fullname, AssemblyDefinition assembly, XPathNavi
 
 		void ProcessType (TypeDefinition type, XPathNavigator nav)
 		{
+			Debug.Assert (ShouldProcessElement (nav));
+
 			IEnumerable<CustomAttribute> attributes = ProcessAttributes (nav);
 			if (attributes.Count () > 0)
 				Context.CustomAttributes.AddCustomAttributes (type, attributes);
@@ -283,9 +286,9 @@ void ProcessSelectedFields (XPathNavigator nav, TypeDefinition type)
 				return;
 
 			while (fields.MoveNext ()) {
-				if (!ShouldProcessElement (fields.Current)) {
-					return;
-				}
+				if (!ShouldProcessElement (fields.Current))
+					continue;
+
 				string value = GetSignature (fields.Current);
 				if (!String.IsNullOrEmpty (value))
 					ProcessFieldSignature (type, value, fields);
@@ -303,9 +306,8 @@ void ProcessSelectedMethods (XPathNavigator nav, TypeDefinition type)
 				return;
 
 			while (methods.MoveNext ()) {
-				if (!ShouldProcessElement (methods.Current)) {
-					return;
-				}
+				if (!ShouldProcessElement (methods.Current))
+					continue;
 
 				string value = GetSignature (methods.Current);
 				if (!String.IsNullOrEmpty (value))
@@ -323,9 +325,8 @@ void ProcessSelectedProperties (XPathNavigator nav, TypeDefinition type)
 			if (properties.Count == 0)
 				return;
 			while (properties.MoveNext ()) {
-				if (!ShouldProcessElement (properties.Current)) {
-					return;
-				}
+				if (!ShouldProcessElement (properties.Current))
+					continue;
 
 				string value = GetSignature (properties.Current);
 				if (!String.IsNullOrEmpty (value))
@@ -343,9 +344,8 @@ void ProcessSelectedEvents (XPathNavigator nav, TypeDefinition type)
 			if (events.Count == 0)
 				return;
 			while (events.MoveNext ()) {
-				if (!ShouldProcessElement (events.Current)) {
-					return;
-				}
+				if (!ShouldProcessElement (events.Current))
+					continue;
 
 				string value = GetSignature (events.Current);
 				if (!String.IsNullOrEmpty (value))
@@ -600,27 +600,6 @@ static PropertyDefinition GetProperty (TypeDefinition type, string signature)
 			return null;
 		}
 
-		bool ShouldProcessElement (XPathNavigator nav)
-		{
-			var feature = GetAttribute (nav, "feature");
-			if (string.IsNullOrEmpty (feature))
-				return true;
-
-			var value = GetAttribute (nav, "featurevalue");
-			if (string.IsNullOrEmpty (value)) {
-				Context.LogError ($"Feature {feature} does not specify a \"featurevalue\" attribute", 1001);
-				return false;
-			}
-
-			if (!bool.TryParse (value, out bool bValue)) {
-				Context.LogError ($"Unsupported non-boolean feature definition {feature}", 1002);
-				return false;
-			}
-
-			if (Context.FeatureSettings == null || !Context.FeatureSettings.TryGetValue (feature, out bool featureSetting))
-				return false;
-
-			return bValue == featureSetting;
-		}
+		bool ShouldProcessElement (XPathNavigator nav) => ResolveFromXmlStep.ShouldProcessElement (nav, Context, _xmlDocumentLocation);
 	}
 }