If ignoring a keyword pattern, restore any previous mapping before returning, otherwise delete the new mapping.

Author: gkellogg

lib/context.js

@@ -495,7 +495,11 @@ api.createTermDefinition = ({
       // FIXME: remove logging and use a handler
       console.warn('WARNING: values beginning with "@" are reserved' +
         ' for future use and ignored', {reverse});
-      activeCtx.mappings.delete(term);
+      if(previousMapping) {
+        activeCtx.mappings.set(term, previousMapping);
+      } else {
+        activeCtx.mappings.delete(term);
+      }
       return;
     }
 
@@ -516,7 +520,11 @@ api.createTermDefinition = ({
       // FIXME: remove logging and use a handler
       console.warn('WARNING: values beginning with "@" are reserved' +
         ' for future use and ignored', {id});
-      activeCtx.mappings.delete(term);
+      if(previousMapping) {
+        activeCtx.mappings.set(term, previousMapping);
+      } else {
+        activeCtx.mappings.delete(term);
+      }
       return;
     } else if(id !== term) {
       // expand and add @id mapping