Comparison helpers should still execute when their key parameter is s…

…et but resolves to undefined.

Previously, if a helper's key parameter was set, but the Dust variable to which it pointed did not exist, the helper would immediately abort. However, this breaks cases especially for {@ne} in which it would be completely valid if the key did not exist.

The helper will still fail to execute if a key parameter is not passed. However, if the parameter resolves to an undefined variable, it will now execute.

This is a non-backwards-compatible change. Closes #59.

lib/dust-helpers.js

@@ -33,18 +33,17 @@ function filter(chunk, context, bodies, params, filterOp) {
       actualKey,
       expectedValue,
       filterOpType = params.filterOpType || '';
+
   // when @eq, @lt etc are used as standalone helpers, key is required and hence check for defined
-  if ( typeof params.key !== "undefined") {
+  if (params.hasOwnProperty("key")) {
     actualKey = dust.helpers.tap(params.key, chunk, context);
-  }
-  else if (isSelect(context)) {
+  } else if (isSelect(context)) {
     actualKey = context.current().selectKey;
     //  supports only one of the blocks in the select to be selected
     if (context.current().isResolved) {
       filterOp = function() { return false; };
     }
-  }
-  else {
+  } else {
     _log("No key specified for filter in:" + filterOpType + " helper ");
     return chunk;
   }
@@ -57,19 +56,17 @@ function filter(chunk, context, bodies, params, filterOp) {
     // we want helpers without bodies to fail gracefully so check it first
     if(body) {
      return chunk.render(body, context);
-    }
-    else {
-      _log("No key specified for filter in:" + filterOpType + " helper ");
+    } else {
+      _log("No body specified for " + filterOpType + " helper ");
       return chunk;
     }
-   }
-   else if (bodies['else']) {
+  } else if (bodies['else']) {
     return chunk.render(bodies['else'], context);
   }
   return chunk;
 }
 
-function coerce (value, type, context) {
+function coerce(value, type, context) {
   if (value) {
     switch (type || typeof(value)) {
       case 'number': return +value;

test/jasmine-test/spec/helpersTests.js

@@ -497,11 +497,25 @@
       },
       {
         name:     "eq helper with no params",
-        source:   "{@eq}Hello{/eq}",
+        source:   "{@eq}Hello{:else}Goodbye{/eq}",
         context:  {},
         expected: "",
         message: "eq helper with no params does not execute"
       },
+      {
+        name:     "eq helper with key that resolves to undefined",
+        source:   "{@eq key=foo value=\"0\"}Hello{:else}Goodbye{/eq}",
+        context:  {},
+        expected: "Goodbye",
+        message:  "eq helper with key that resolves to undefined uses that as comparison"
+      },
+      {
+        name:     "eq helper with both key and value undefined",
+        source:   "{@eq key=foo value=bar}Hello{:else}Goodbye{/eq}",
+        context:  {},
+        expected: "Hello",
+        message:  "eq helper with key and value that both resolve to undefined is true"
+      },
       {
         name:     "eq helper matching string case",
         source:   "{@eq key=\"foo\" value=\"foo\"}equal{/eq}",