Repository: ViacomInc/data-point (js)

Issue:
implement isPlainObject on ConstantReducer
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**Problem description**:

https://github.com/ViacomInc/data-point/pull/383#discussion_r316423143


**Suggested solution**:

On ConstantReducer.resolve only execute cloneDeep if its a plain object, meaning move the isPlainObject out of the existing module to a place where its common and can be used by both.

Pull request:
 constant check object
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<!-- What changes are being made? (What feature/bug is being fixed here?) -->
**What**:

closes #386 

<!-- Why are these changes necessary? -->
**Why**:

As per discusses in https://github.com/ViacomInc/data-point/pull/383#discussion_r316423143

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- [ ] Has Breaking changes
- [ ] Documentation
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Patch:
diff --git a/packages/data-point/src/ReducerObject.js b/packages/data-point/src/ReducerObject.js
index 9878c94..cc6e76d 100644
--- a/packages/data-point/src/ReducerObject.js
+++ b/packages/data-point/src/ReducerObject.js
@@ -3,12 +3,7 @@ const cloneDeep = require("lodash/cloneDeep");
 
 const { Reducer } = require("./Reducer");
 const isReducerConstant = require("./is-reducer-constant");
-
-function isPlainObject(obj) {
-  return (
-    typeof obj === "object" && Object.getPrototypeOf(obj) === Object.prototype
-  );
-}
+const isPlainObject = require("./is-plain-object");
 
 function newProps() {
   return {
diff --git a/packages/data-point/src/is-plain-object.js b/packages/data-point/src/is-plain-object.js
new file mode 100644
index 0000000..dbc99bc
--- /dev/null
+++ b/packages/data-point/src/is-plain-object.js
@@ -0,0 +1,6 @@
+function isPlainObject(obj) {
+  return (
+    typeof obj === "object" && Object.getPrototypeOf(obj) === Object.prototype
+  );
+}
+module.exports = isPlainObject;
diff --git a/packages/data-point/src/reducer-helpers/constant/constant.js b/packages/data-point/src/reducer-helpers/constant/constant.js
index 9651262..7688752 100644
--- a/packages/data-point/src/reducer-helpers/constant/constant.js
+++ b/packages/data-point/src/reducer-helpers/constant/constant.js
@@ -1,14 +1,24 @@
 const cloneDeep = require("lodash/cloneDeep");
 
 const { Reducer } = require("../../Reducer");
+const isPlainObject = require("../../is-plain-object");
+
+/**
+ * @param {Boolean} isObject true if parameter `value` is assumed to be an object
+ * @param {any} value
+ */
+function cloneObject(isObject, value) {
+  return isObject ? cloneDeep(value) : value;
+}
 
 class ReducerConstant extends Reducer {
   constructor(spec) {
     super("constant", undefined, spec);
+    this.isPlainObject = isPlainObject(spec);
     // We clone the source to truly respect the nature of a constant, if the
     // original source is ever changed the data integrity of the constant
     // should be kept
-    this.constantValue = cloneDeep(spec);
+    this.constantValue = cloneObject(this.isPlainObject, spec);
   }
 
   static create(spec) {
@@ -21,10 +31,11 @@ class ReducerConstant extends Reducer {
   resolve() {
     // this clone happens so any future changes to the output do not
     // affect the original value of this.constantValue
-    return cloneDeep(this.constantValue);
+    return cloneObject(this.isPlainObject, this.constantValue);
   }
 }
 
 module.exports = {
+  cloneObject,
   ReducerConstant
 };


Test patch:
diff --git a/packages/data-point/src/ReducerObject.test.js b/packages/data-point/src/ReducerObject.test.js
index 212b712..4c0f479 100644
--- a/packages/data-point/src/ReducerObject.test.js
+++ b/packages/data-point/src/ReducerObject.test.js
@@ -15,19 +15,6 @@ afterEach(() => {
   jest.clearAllMocks();
 });
 
-describe("isPlainObject", () => {
-  it("should return true for plain objects", () => {
-    expect(reducerObject.isPlainObject({})).toEqual(true);
-    expect(reducerObject.isPlainObject("string")).toEqual(false);
-    expect(reducerObject.isPlainObject(123)).toEqual(false);
-    expect(reducerObject.isPlainObject(() => true)).toEqual(false);
-
-    expect(reducerObject.isPlainObject(Object.create({}))).toEqual(false);
-    class Test {}
-    expect(reducerObject.isPlainObject(new Test())).toEqual(false);
-  });
-});
-
 describe("getObjectProperties", () => {
   it("should extract all constant", () => {
     const obj = {
diff --git a/packages/data-point/src/is-plain-object.test.js b/packages/data-point/src/is-plain-object.test.js
new file mode 100644
index 0000000..6c113ed
--- /dev/null
+++ b/packages/data-point/src/is-plain-object.test.js
@@ -0,0 +1,14 @@
+const isPlainObject = require("./is-plain-object");
+
+describe("isPlainObject", () => {
+  it("should return true for plain objects", () => {
+    expect(isPlainObject({})).toEqual(true);
+    expect(isPlainObject("string")).toEqual(false);
+    expect(isPlainObject(123)).toEqual(false);
+    expect(isPlainObject(() => true)).toEqual(false);
+
+    expect(isPlainObject(Object.create({}))).toEqual(false);
+    class Test {}
+    expect(isPlainObject(new Test())).toEqual(false);
+  });
+});
diff --git a/packages/data-point/src/reducer-helpers/constant/constant.test.js b/packages/data-point/src/reducer-helpers/constant/constant.test.js
index 311d020..c47266e 100644
--- a/packages/data-point/src/reducer-helpers/constant/constant.test.js
+++ b/packages/data-point/src/reducer-helpers/constant/constant.test.js
@@ -1,4 +1,29 @@
-const { ReducerConstant } = require("./constant");
+jest.mock("lodash/cloneDeep");
+const mockCloneDeep = require("lodash/cloneDeep");
+
+mockCloneDeep.mockImplementation(jest.requireActual("lodash/cloneDeep"));
+
+const { ReducerConstant, cloneObject } = require("./constant");
+
+afterEach(() => {
+  jest.clearAllMocks();
+});
+
+describe("cloneObject", () => {
+  it("should not clone if parameter isObject is passed as false", () => {
+    const result = cloneObject(false, "string");
+    expect(mockCloneDeep).not.toBeCalled();
+    expect(result).toEqual("string");
+  });
+
+  it("should clone if parameter isObject is passed as true", () => {
+    const source = {};
+    const result = cloneObject(true, source);
+    expect(mockCloneDeep).toBeCalled();
+    source.mutated = true;
+    expect(result).toEqual({});
+  });
+});
 
 describe("ReducerConstant", () => {
   describe("constructor", () => {
@@ -12,6 +37,13 @@ describe("ReducerConstant", () => {
       expect(reducer.constantValue).toEqual("value");
     });
 
+    it("should not clone non-plain objects", () => {
+      const reducer = new ReducerConstant(true);
+
+      expect(reducer.constantValue).toEqual(true);
+      expect(mockCloneDeep).not.toBeCalled();
+    });
+
     it("should set constantValue to be deep cloned from source received", () => {
       const sourceObject = {
         test: "test"
@@ -44,7 +76,7 @@ describe("ReducerConstant", () => {
       expect(reducer.resolve()).toEqual(sourceObject);
     });
 
-    it("should return deep cloned value", () => {
+    it("should return deep cloned value for plain objects", () => {
       const sourceObject = {
         test: "test"
       };
@@ -57,5 +89,12 @@ describe("ReducerConstant", () => {
         test: "test"
       });
     });
+
+    it("should return value for non-plain objects", () => {
+      const reducer = ReducerConstant.create("string");
+      const result = reducer.resolve();
+      expect(result).toEqual("string");
+      expect(mockCloneDeep).not.toBeCalled();
+    });
   });
 });