WIP1-4p

commitlint/fpHelpers.ts

@@ -53,6 +53,11 @@ export class OptionStatic {
 export class TypeHelpers {
     // because instanceof doesn't work with primitive types (e.g. String), taken from https://stackoverflow.com/a/58184883/544947
     public static IsInstanceOf(variable: any, type: any) {
+        if (variable === null || variable === undefined) {
+            throw new Error(
+                "Invalid 'variable' parameter passed in: null or undefined"
+            );
+        }
         let res: boolean = false;
         if (typeof type == "string") {
             res = typeof variable == type.toLowerCase();

commitlint/tests/testHelpers.ts

@@ -89,6 +89,29 @@ test("testing TypeHelpers.IsInstanceOf", () => {
     expect(TypeHelpers.IsInstanceOf(bar, Foo)).toBe(false);
 });
 
+test("testing TypeHelpers.IsInstanceOf exceptions", () => {
+    let strNull = null;
+    expect(() => TypeHelpers.IsInstanceOf(strNull, String)).toThrowError(
+        "Invalid"
+    );
+    expect(() => TypeHelpers.IsInstanceOf(strNull, String)).toThrowError(
+        "parameter"
+    );
+    expect(() => TypeHelpers.IsInstanceOf(strNull, String)).toThrowError(
+        "null"
+    );
+    let strUndefined = undefined;
+    expect(() => TypeHelpers.IsInstanceOf(strUndefined, String)).toThrowError(
+        "Invalid"
+    );
+    expect(() => TypeHelpers.IsInstanceOf(strUndefined, String)).toThrowError(
+        "parameter"
+    );
+    expect(() => TypeHelpers.IsInstanceOf(strUndefined, String)).toThrowError(
+        "undefined"
+    );
+});
+
 export function runCommitLintOnMsg(inputMsg: string) {
     // FIXME: should we .lowerCase().startsWith("win") in case it starts
     // returning Win64 in the future? thing is, our CI doesn't like this