ADD metadata in JEXL context

CHANGES_NEXT_RELEASE

@@ -1,4 +1,5 @@
 - Add: custom notification ngsi patching evaluation priority based in evalPriority builtin metadata (#4556)
+- Add: attribute metadata to JEXL context (#4594)
 - Fix: $max and $min operators were not supported with DateTime attributes (#4585)
 - Fix: wrong date values should not allowed in subscription's expires field (#4541)
 - Fix: do not raise DB alarm in case of wrong GeoJSON in client request

doc/manuals/orion-api.md

@@ -75,6 +75,7 @@
       - [Additional considerations](#additional-considerations)
     - [JEXL Support](#jexl-support)
       - [JEXL usage example](#jexl-usage-example)
+      - [Metadata support](#metadata-support)
       - [Evaluation priority](#evaluation-priority)
       - [Available Transformations](#available-transformations)
         - [`uppercase`](#uppercase)
@@ -2514,6 +2515,19 @@ will trigger a notification like this:
 ]
 ```
 
+### Metadata support
+
+Attribute metadata is also included in the JEXL evaluation context, along with the actual attributes. This is done using a special context key named `metadata` which value is an object with the following structure:
+
+* keys are the name of the attributes
+* values are object with a key-map of the metadata values of the given attribute
+
+For instance, the expression `${metadata.A.MD1}` will result in the value of the metadata `MD1` belonging to the attribute `A`.
+
+Note that [builtin metadata](#builtin-metadata) are automatically added to the `metadata` context key. For instance, the `${A-metadata.A.previousValue}` expression will provide the difference between the current value of `A` (in the update request) and the previous one (before the update request).
+
+Finally, note that in the rare case an attribute named `metadata` is used (which is an anti-pattern strongly discouraged) it will not be added to the context, as the `metadata` with metadata values will take precedence.
+
 ### Evaluation priority
 
 Each time an expression is evaluated, it is added to the expression context, so it can be reused by other expressions. However, by default Orion does not guarantee a given evaluation other.

src/lib/ngsi/Metadata.cpp

@@ -666,3 +666,71 @@ void Metadata::appendToBsoN(orion::BSONObjBuilder* mdBuilder, orion::BSONArrayBu
     }
   }
 }
+
+
+/* ****************************************************************************
+*
+* addToContext -
+*
+* FIXME P5: duplicated from ContextAttrMetibute::addToContext(). Maybe they should be unified
+*/
+void Metadata::addToContext(ExprContextObject* exprContextObjectP, bool legacy)
+{
+  if (compoundValueP != NULL)
+  {
+    // In legacy expression, objects are vector are strings to be stored in a std::map<std::string,std::string>
+    if (valueType == orion::ValueTypeObject)
+    {
+      if (legacy)
+      {
+        exprContextObjectP->add(name, compoundValueP->toJson(), true);
+      }
+      else
+      {
+        exprContextObjectP->add(name, compoundValueP->toExprContextObject());
+      }
+    }
+    else  // valueType == orion::ValueTypeVector
+    {
+      if (legacy)
+      {
+        exprContextObjectP->add(name, compoundValueP->toJson(), true);
+      }
+      else
+      {
+        exprContextObjectP->add(name, compoundValueP->toExprContextList());
+      }
+    }
+  }
+  else if (valueType == orion::ValueTypeNumber)
+  {
+    if ((type == DATE_TYPE) || (type == DATE_TYPE_ALT))
+    {
+      exprContextObjectP->add(name, toJsonString(isodate2str(numberValue)));
+    }
+    else // regular number
+    {
+      exprContextObjectP->add(name, numberValue);
+    }
+  }
+  else if (valueType == orion::ValueTypeString)
+  {
+    exprContextObjectP->add(name, toJsonString(stringValue));
+  }
+  else if (valueType == orion::ValueTypeBoolean)
+  {
+    exprContextObjectP->add(name, boolValue);
+  }
+  else if (valueType == orion::ValueTypeNull)
+  {
+    exprContextObjectP->add(name);
+  }
+  else if (valueType == orion::ValueTypeNotGiven)
+  {
+    LM_E(("Runtime Error (value not given for metadata %s)", name.c_str()));
+  }
+  else
+  {
+    LM_E(("Runtime Error (invalid value type %s for metadata %s)", valueTypeName(valueType), name.c_str()));
+  }
+}

src/lib/ngsi/Metadata.h

@@ -98,6 +98,8 @@ typedef struct Metadata
 
   void         appendToBsoN(orion::BSONObjBuilder* md, orion::BSONArrayBuilder* mdNames, bool useDefaultType);
 
+  void         addToContext(ExprContextObject* exprContextObjectP, bool legacy);
+
   std::string  check(ApiVersion apiVersion);
 } Metadata;
 

src/lib/ngsiNotify/Notifier.cpp

@@ -367,6 +367,7 @@ static SenderThreadParams* buildSenderParamsCustom
 
   // Used by several macroSubstitute() calls along this function
   ExprContextObject exprContext(basic);
+  ExprContextObject exprMetadataContext(basic);
 
   // It seems that add() semantics are different in basic and jexl mode. In jexl mode, if the key already exists, it is
   // updated (in other words, the last added keys is the one that takes precedence). In basic model, if the key already
@@ -376,16 +377,31 @@ static SenderThreadParams* buildSenderParamsCustom
   TIME_EXPR_CTXBLD_START();
   exprContext.add("id", en.id);
   exprContext.add("type", en.type);
+
   if (!basic)
   {
     exprContext.add("service", tenant);
     exprContext.add("servicePath", en.servicePath);
     exprContext.add("authToken", xauthToken);
   }
+
   for (unsigned int ix = 0; ix < en.attributeVector.size(); ix++)
   {
     en.attributeVector[ix]->addToContext(&exprContext, basic);
+
+    // Add attribute metadata to context
+    ExprContextObject exprAttrMetadataContext(basic);
+    for (unsigned int jx = 0; jx < en.attributeVector[ix]->metadataVector.size(); jx++)
+    {
+      en.attributeVector[ix]->metadataVector[jx]->addToContext(&exprAttrMetadataContext, basic);
+    }
+    exprMetadataContext.add(en.attributeVector[ix]->name, exprAttrMetadataContext);
   }
+
+  // Add all metadata under the "metadata" context key
+  // (note that in JEXL if the key already exists, it is updated, so attribute with name "metadata" will never be appear in context)
+  exprContext.add("metadata", exprMetadataContext);
+
   if (basic)
   {
     exprContext.add("service", tenant);