Fix isBoundToPoint function implementation (#550)

* Fix `isBoundToPoint` function implementation

* adds test cases

* uses 'defined' function of CHARTJS helpers

Author: stockiNail

src/helpers/helpers.options.js

@@ -1,4 +1,4 @@
-import {isObject, valueOrDefault} from 'chart.js/helpers';
+import {isObject, valueOrDefault, defined} from 'chart.js/helpers';
 
 const isEnabled = (options) => options && (options.display || options.enabled);
 const toPercent = (s) => typeof s === 'string' && s.endsWith('%') && parseFloat(s) / 100;
@@ -52,5 +52,5 @@ export function toPosition(value) {
 }
 
 export function isBoundToPoint(options) {
-  return options && (options.xValue || options.yValue);
+  return options && (defined(options.xValue) || defined(options.yValue));
 }

test/fixtures/point/boundToPoint0.js

@@ -0,0 +1,39 @@
+module.exports = {
+  tolerance: 0.0055,
+  config: {
+    type: 'scatter',
+    options: {
+      scales: {
+        x: {
+          display: true,
+          min: -10,
+          max: 10
+        },
+        y: {
+          display: true,
+          min: -4,
+          max: 10
+        }
+      },
+      plugins: {
+        legend: false,
+        annotation: {
+          drawTime: 'afterDraw',
+          annotations: {
+            point: {
+              type: 'point',
+              xScaleID: 'x',
+              yScaleID: 'y',
+              xValue: 0,
+              yValue: 0,
+              backgroundColor: 'rgba(101, 33, 171, 0.5)',
+              borderColor: 'rgb(101, 33, 171)',
+              borderWidth: 15,
+              radius: 50
+            }
+          }
+        }
+      }
+    }
+  }
+};

test/fixtures/point/boundToPoint0.png

@@ -0,0 +1,40 @@
+module.exports = {
+  tolerance: 0.0055,
+  config: {
+    type: 'scatter',
+    options: {
+      scales: {
+        x: {
+          display: true,
+          min: -10,
+          max: 10
+        },
+        y: {
+          display: true,
+          min: -4,
+          max: 10
+        }
+      },
+      plugins: {
+        legend: false,
+        annotation: {
+          drawTime: 'afterDraw',
+          annotations: {
+            polygon: {
+              type: 'polygon',
+              xScaleID: 'x',
+              yScaleID: 'y',
+              xValue: 0,
+              yValue: 0,
+              sides: 5,
+              backgroundColor: 'rgba(101, 33, 171, 0.5)',
+              borderColor: 'rgb(101, 33, 171)',
+              borderWidth: 15,
+              radius: 50
+            }
+          }
+        }
+      }
+    }
+  }
+};