Retain Extra fields over Uses,Augments (#244)

* Retain Extra fields over Uses,Augments

* Fix duplication issue; add IfFeature test for uses in augment

* Add comments to entry_test

pkg/yang/entry.go

@@ -1461,6 +1461,12 @@ func (e *Entry) dup() *Entry {
 			ne.Dir[k] = de
 		}
 	}
+
+	ne.Extra = make(map[string][]interface{})
+	for k, v := range e.Extra {
+		ne.Extra[k] = v
+	}
+
 	return &ne
 }
 
@@ -1485,6 +1491,9 @@ func (e *Entry) merge(prefix *Value, namespace *Value, oe *Entry) {
 		} else {
 			v.Parent = e
 			v.Exts = append(v.Exts, oe.Exts...)
+			for lk := range oe.Extra {
+				v.Extra[lk] = append(v.Extra[lk], oe.Extra[lk]...)
+			}
 			e.Dir[k] = v
 		}
 	}

pkg/yang/entry_test.go

@@ -2058,6 +2058,7 @@ var testIfFeatureModules = []struct {
   feature ft-identity;
   feature ft-uses;
   feature ft-refine;
+  feature ft-augment-uses;
 
   container cont {
     if-feature ft-container;
@@ -2118,6 +2119,9 @@ var testIfFeatureModules = []struct {
 
   augment "/cont" {
     if-feature ft-augment;
+	uses g {
+		if-feature ft-augment-uses;
+	}
   }
 
   identity id {
@@ -2130,7 +2134,10 @@ var testIfFeatureModules = []struct {
       if-feature ft-refine;
     }
   }
-  grouping g {}
+
+  grouping g {
+	container gc {}
+  }
 }
 `,
 	},
@@ -2269,6 +2276,18 @@ func TestIfFeature(t *testing.T) {
 			inIfFeatures:   ms.Modules["if-feature"].Uses[0].IfFeature,
 			wantIfFeatures: []string{"ft-uses"},
 		},
+		{
+			// Verify that if-feature field defined in "uses" is correctly propagated to container
+			name:           "uses",
+			inIfFeatures:   entryIfFeatures(mod.Dir["gc"]),
+			wantIfFeatures: []string{"ft-uses"},
+		},
+		{
+			// Verify that if-feature field defined in "augment" and in "augment > uses" is correctly propagated to container
+			name:           "augment-uses",
+			inIfFeatures:   entryIfFeatures(mod.Dir["cont"].Dir["gc"]),
+			wantIfFeatures: []string{"ft-augment-uses", "ft-augment"},
+		},
 	}
 
 	for _, tc := range testcases {