Fix clearing with @context:null.

- Use `undefined` vs `null` for getContextValue(ctx, key, '@context').

Author: davidlehn

lib/compact.js

@@ -8,7 +8,8 @@ const JsonLdError = require('./JsonLdError');
 const {
   isArray: _isArray,
   isObject: _isObject,
-  isString: _isString
+  isString: _isString,
+  isUndefined: _isUndefined
 } = require('./types');
 
 const {
@@ -100,7 +101,7 @@ api.compact = ({
 
   // use any scoped context on activeProperty
   const ctx = _getContextValue(activeCtx, activeProperty, '@context');
-  if(ctx) {
+  if(!_isUndefined(ctx)) {
     activeCtx = _processContext({activeCtx, localCtx: ctx, options});
   }
 
@@ -156,7 +157,7 @@ api.compact = ({
 
       // Use any scoped context defined on this value
       const ctx = _getContextValue(activeCtx, compactedType, '@context');
-      if(ctx) {
+      if(!_isUndefined(ctx)) {
         activeCtx = _processContext({activeCtx, localCtx: ctx, options});
       }
     }

lib/context.js

@@ -874,18 +874,21 @@ api.getInitialContext = options => {
 
 /**
  * Gets the value for the given active context key and type, null if none is
- * set.
+ * set or undefined if none is set and type is '@context'.
  *
  * @param ctx the active context.
  * @param key the context key.
  * @param [type] the type of value to get (eg: '@id', '@type'), if not
  *          specified gets the entire entry for a key, null if not found.
  *
- * @return the value.
+ * @return the value, null, or undefined.
  */
 api.getContextValue = (ctx, key, type) => {
-  // return null for invalid key
+  // invalid key
   if(key === null) {
+    if(type === '@context') {
+      return undefined;
+    }
     return null;
   }
 
@@ -908,6 +911,9 @@ api.getContextValue = (ctx, key, type) => {
     return ctx[type];
   }
 
+  if(type === '@context') {
+    return undefined;
+  }
   return null;
 };
 

lib/expand.js

@@ -9,7 +9,8 @@ const {
   isArray: _isArray,
   isObject: _isObject,
   isEmptyObject: _isEmptyObject,
-  isString: _isString
+  isString: _isString,
+  isUndefined: _isUndefined
 } = require('./types');
 
 const {
@@ -165,7 +166,7 @@ api.expand = ({
           (value.length > 1 ? value.slice().sort() : value) : [value];
       for(const type of types) {
         const ctx = _getContextValue(activeCtx, type, '@context');
-        if(ctx) {
+        if(!_isUndefined(ctx)) {
           activeCtx = _processContext({activeCtx, localCtx: ctx, options});
         }
       }
@@ -555,7 +556,7 @@ function _expandObject({
     // use potential scoped context for key
     let termCtx = activeCtx;
     const ctx = _getContextValue(activeCtx, key, '@context');
-    if(ctx) {
+    if(!_isUndefined(ctx)) {
       termCtx = _processContext({
         activeCtx, localCtx: ctx, options, propertyTermDefinition: true
       });
@@ -832,7 +833,7 @@ function _expandIndexMap(
   for(let key of keys) {
     // if indexKey is @type, there may be a context defined for it
     const ctx = _getContextValue(activeCtx, key, '@context');
-    if(ctx) {
+    if(!_isUndefined(ctx)) {
       activeCtx = _processContext({activeCtx, localCtx: ctx, options});
     }