throw error in mergeWith method if no merger is passed (#1503)

Brandon Lawrence · Brandon Lawrence · commit 29161610c18e · 2018-06-15T08:22:24.000-04:00
diff --git a/__tests__/merge.ts b/__tests__/merge.ts
@@ -40,6 +40,12 @@ describe('merge', () => {
     );
   });
 
+  it('throws typeError without merge function', () => {
+    const m1 = Map({ a: 1, b: 2, c: 3 });
+    const m2 = Map({ d: 10, b: 20, e: 30 });
+    expect(() => m1.mergeWith(1, m2)).toThrowError(TypeError);
+  });
+
   it('provides key as the third argument of merge function', () => {
     const m1 = Map({ id: 'temp', b: 2, c: 3 });
     const m2 = Map({ id: 10, b: 20, e: 30 });
diff --git a/src/functional/merge.js b/src/functional/merge.js
@@ -38,7 +38,8 @@ export function mergeWithSources(collection, sources, merger) {
     );
   }
   if (isImmutable(collection)) {
-    return collection.mergeWith
+    const shouldMergeWith = collection.mergeWith && merger instanceof Function;
+    return shouldMergeWith
       ? collection.mergeWith(merger, ...sources)
       : collection.concat(...sources);
   }
diff --git a/src/methods/merge.js b/src/methods/merge.js
@@ -14,7 +14,10 @@ export function merge(...iters) {
 }
 
 export function mergeWith(merger, ...iters) {
-  return mergeIntoKeyedWith(this, iters, merger);
+  if (merger instanceof Function) {
+    return mergeIntoKeyedWith(this, iters, merger);
+  }
+  throw new TypeError('Invalid merger: Expected Function');
 }
 
 function mergeIntoKeyedWith(collection, collections, merger) {

Original file line number	Diff line number	Diff line change
`@@ -38,7 +38,8 @@ export function mergeWithSources(collection, sources, merger) {`
`38`	`38`	`);`
`39`	`39`	`}`
`40`	`40`	`if (isImmutable(collection)) {`
`41`		`- return collection.mergeWith`
	`41`	`+ const shouldMergeWith = collection.mergeWith && merger instanceof Function;`
	`42`	`+ return shouldMergeWith`
`42`	`43`	`? collection.mergeWith(merger, ...sources)`
`43`	`44`	`: collection.concat(...sources);`
`44`	`45`	`}`
Original file line number	Diff line number	Diff line change
`@@ -14,7 +14,10 @@ export function merge(...iters) {`
`14`	`14`	`}`
`15`	`15`
`16`	`16`	`export function mergeWith(merger, ...iters) {`
`17`		`- return mergeIntoKeyedWith(this, iters, merger);`
	`17`	`+ if (merger instanceof Function) {`
	`18`	`+ return mergeIntoKeyedWith(this, iters, merger);`
	`19`	`+ }`
	`20`	`+ throw new TypeError('Invalid merger: Expected Function');`
`18`	`21`	`}`
`19`	`22`
`20`	`23`	`function mergeIntoKeyedWith(collection, collections, merger) {`