feat(core): Added the Attributes.setIfUnset() method

config/changelog.yaml

@@ -1,3 +1,9 @@
+unreleased:
+
+  Added:
+    core:
+      - Added the new attributes.setIfUnset() method
+
 2.19.5:
   date: 2022-11-13
 

markdown/dev/reference/api/attributes/setifunset/en.md

@@ -0,0 +1,24 @@
+---
+title: setIfUnset()
+---
+
+```js
+Attributes attributes.setIfUnset(string key, string value)
+```
+
+Sets the attribute identified by `key` to value `value` but only if it's currently unset (`undefined`).
+
+<Tip>
+
+This will never overwrite any value and thus is a safe way to set attributes
+
+</Tip>
+
+```js
+let { Path, paths } = part.shorthand();
+
+// This will render as: class="classA"
+paths.demo = new Path();
+paths.demo.attributes.set('class', 'classA');
+paths.demo.attributes.setIfUnset('class', 'classB');
+```

packages/core/src/attributes.js

@@ -19,6 +19,13 @@ Attributes.prototype.set = function (name, value) {
   return this
 }
 
+/** Sets an attribute, but only if it's not currently set */
+Attributes.prototype.setIfUnset = function (name, value) {
+  if (typeof this.list[name] === 'undefined') this.list[name] = [value]
+
+  return this
+}
+
 /** Removes an attribute */
 Attributes.prototype.remove = function (name) {
   delete this.list[name]

packages/core/tests/attributes.test.js

@@ -1,9 +1,25 @@
-let expect = require("chai").expect;
+const expect = require("chai").expect;
-let Point = require("./dist").Point;
+const Point = require("./dist").Point;
 
-function newAttr() {
+const newAttr = () => new Point(0, 0).attributes;
-  return new Point(0, 0).attributes;
+
-}
+const a = newAttr();
+it("Should set an attribute", () => {
+  a.set('hold', 'me')
+  expect(a.get("hold")).to.equal('me');
+});
+
+it("Should remove an attribute", () => {
+  a.remove('hold')
+  expect(a.get("hold")).to.equal(false);
+});
+
+it("Should only set an unset attribute", () => {
+  a.setIfUnset('hold', 'me')
+  expect(a.get("hold")).to.equal('me');
+  a.setIfUnset('hold', 'thatDudeOverThere')
+  expect(a.get("hold")).to.equal('me');
+});
 
 it("Should return false when getting an unset attribute", () => {
   let a = newAttr();