fix(lib): Ensure match and match_phrase handle empty Variables

We want the match and match_phrase helper functions to gracefully handle
the case where a variable has no value, which internally is an empty
string.

This requires doing an explicit comparison to ensure that optional
parameters are not set unless the variable is actually defined.

lib/leaf/match.js

@@ -25,7 +25,7 @@ module.exports = function( property, value, params) {
   };
 
   optional_params.forEach(function(param) {
-    if (params && params[param]) {
+    if (params && params[param] && params[param].toString() !== '') {
       query.match[property][param] = params[param];
     }
   });

lib/leaf/match_phrase.js

@@ -14,7 +14,7 @@ module.exports = function( property, value, params ) {
   const optional_params = ['boost', 'slop', 'analyzer'];
 
   optional_params.forEach(function(param) {
-    if (params && params[param]) {
+    if (params && params[param] && params[param].toString() !== '') {
       query.match_phrase[property][param] = params[param];
     }
   });

test/lib/leaf/match.js

@@ -1,4 +1,5 @@
 const match = require('../../../lib/leaf/match');
+const Variable = require('../../../lib/Variable');
 
 module.exports.tests = {};
 
@@ -127,6 +128,36 @@ module.exports.tests.match = function(test, common) {
     t.deepEqual(query, expected, 'valid match query with analyzer');
     t.end();
   });
+
+  test('match query does not allow empty string as optional param value', function(t) {
+    const query = match('property', 'value', { analyzer: ''});
+
+    const expected = {
+      match: {
+        property: {
+          query: 'value'
+        }
+      }
+    };
+
+    t.deepEqual(query, expected, 'valid match query with out empty string value');
+    t.end();
+  });
+
+  test('match query does not allow empty Variable as optional param value', function(t) {
+    const query = match('property', 'value', { analyzer: new Variable() });
+
+    const expected = {
+      match: {
+        property: {
+          query: 'value'
+        }
+      }
+    };
+
+    t.deepEqual(query, expected, 'valid match query with out empty string value');
+    t.end();
+  });
 };
 
 module.exports.all = function (tape, common) {

test/lib/leaf/match_phrase.js

@@ -1,4 +1,5 @@
 const match_phrase = require('../../../lib/leaf/match_phrase');
+const Variable = require('../../../lib/Variable');
 
 module.exports.tests = {};
 
@@ -79,6 +80,36 @@ module.exports.tests.match_phrase = function(test, common) {
     t.deepEqual(query, expected, 'valid match_phrase query with analyzer');
     t.end();
   });
+
+  test('match_phrase query does not allow empty string as optional param value', function(t) {
+    const query = match_phrase('property', 'value', { slop: '' });
+
+    const expected = {
+      match_phrase: {
+        property: {
+          query: 'value'
+        }
+      }
+    };
+
+    t.deepEqual(query, expected, 'valid match_phrase query without empty string value');
+    t.end();
+  });
+
+  test('match_phrase query does not allow empty Variable as optional param value', function(t) {
+    const query = match_phrase('property', 'value', { analyzer: new Variable() });
+
+    const expected = {
+      match_phrase: {
+        property: {
+          query: 'value'
+        }
+      }
+    };
+
+    t.deepEqual(query, expected, 'valid match_phrase query with out empty string value');
+    t.end();
+  });
 };
 
 module.exports.all = function (tape, common) {