fix: flag required params as missing when explicitly undefined, null,…

… or an empty string (#90)

before, we were checking for "truthyness". when required params were set to `false`, they were incorrectly being flagged as missing.

lib/helper.ts

@@ -113,8 +113,8 @@ export function getMissingParams(
     missing = requires;
   } else {
     missing = [];
-    requires.forEach((require) => {
-      if (!params[require]) {
+    requires.forEach(require => {
+      if (isMissing(params[require])) {
         missing.push(require);
       }
     });
@@ -124,6 +124,17 @@ export function getMissingParams(
     : null;
 }
 
+/**
+ * Returns true if value is determined to be "missing". Currently defining "missing"
+ * as `undefined`, `null`, or the empty string.
+ *
+ * @param value - the parameter value
+ * @returns boolean
+ */
+function isMissing(value: any): boolean {
+  return value === undefined || value === null || value === '';
+}
+
 /**
  * Return true if 'text' is html
  * @param  {string} text - The 'text' to analyze

test/unit/get-missing-params.test.js

@@ -64,4 +64,8 @@ describe('getMissingParams', function() {
       'Missing required parameters: a, b'
     );
   });
+
+  it('should not throw an error if a required parameter is given and set to false', function() {
+    expect(getMissingParams({ a: 'a', b: false }, ['a', 'b'])).toBeNull();
+  });
 });