Implement deep compare for term definitions.

Author: dlongley

lib/context.js

@@ -664,7 +664,7 @@ api.createTermDefinition = (
     // be equal
     activeCtx.protected[term] = true;
     mapping.protected = true;
-    if(!_areTermDefinitionsEqual(previousMapping, mapping)) {
+    if(!_deepCompare(previousMapping, mapping)) {
       const protectedMode = (options && options.protectedMode) || 'error';
       if(protectedMode === 'error') {
         throw new JsonLdError(
@@ -1317,42 +1317,45 @@ function _findContextUrls(input, urls, replace, base) {
   }
 }
 
-function _areTermDefinitionsEqual(d1, d2) {
-  const k1 = Object.keys(d1);
-  const k2 = Object.keys(d2);
-  if(k1.length !== k2.length) {
+function _deepCompare(x1, x2) {
+  // compare `null` or primitive types directly
+  if((!(x1 && typeof x1 === 'object')) ||
+     (!(x2 && typeof x2 === 'object'))) {
+    return x1 === x2;
+  }
+  // x1 and x2 are objects (also potentially arrays)
+  const x1Array = Array.isArray(x1);
+  if(x1Array !== Array.isArray(x2)) {
     return false;
   }
-
-  for(const k of k1) {
-    const v1 = d1[k];
-    const v2 = d2[k];
-    if(k === '@context') {
-      // FIXME: temporary hack, use deep comparison instead
-      if(JSON.stringify(v1) !== JSON.stringify(v2)) {
-        return false;
-      }
-      continue;
-    }
-    const isArray = Array.isArray(v1);
-    if(isArray !== Array.isArray(v2)) {
+  if(x1Array) {
+    if(x1.length !== x2.length) {
       return false;
     }
-    // `@container`
-    if(isArray) {
-      if(v1.length !== v2.length) {
+    for(let i = 0; i < x1.length; ++i) {
+      if(!_deepCompare(x1[i], x2[i])) {
         return false;
       }
-      v1.sort();
-      v2.sort();
-      for(let i = 0; i < v1.length; ++i) {
-        if(v1[i] !== v2[i]) {
-          return false;
-        }
+    }
+    return true;
+  }
+  // x1 and x2 are non-array objects
+  const k1s = Object.keys(x1);
+  const k2s = Object.keys(x2);
+  if(k1s.length !== k2s.length) {
+    return false;
+  }
+  for(const k1 in x1) {
+    let v1 = x1[k1];
+    let v2 = x2[k1];
+    // special case: `@container` can be in any order
+    if(k1 === '@container') {
+      if(Array.isArray(v1) && Array.isArray(v2)) {
+        v1 = v1.slice().sort();
+        v2 = v2.slice().sort();
       }
     }
-    // strings
-    if(v1 !== v2) {
+    if(!_deepCompare(v1, v2)) {
       return false;
     }
   }