fix: rounding values on stacked w percentage charts

.playground/tsconfig.json

@@ -2,7 +2,8 @@
   "extends": "../tsconfig",
   "compilerOptions": {
     "downlevelIteration": true,
-    "target": "es5"
+    "target": "es5",
+    "resolveJsonModule": true
   },
   "include": ["../src/**/*", "./**/*"],
   "exclude": ["../**/*.test.*"]

src/chart_types/xy_chart/utils/stacked_series_utils.ts

@@ -29,6 +29,7 @@ import {
 
 import { SeriesKey } from '../../../common/series_id';
 import { ScaleType } from '../../../scales/constants';
+import { clamp } from '../../../utils/common';
 import { DataSeries, DataSeriesDatum } from './series';
 import { StackMode } from './specs';
 
@@ -137,8 +138,14 @@ export function formatStackedDataSeriesValues(
         const { initialY0, initialY1, mark, datum, filled } = originalData;
         return {
           x,
-          y1,
-          y0,
+          /**
+           * Due to floating point errors, values computed on a stack
+           * could falls out of the current defined domain boundaries.
+           * This in particular cause issues with percent stack, where the domain
+           * is hardcoded to [0,1] and some value can fall outside that domain.
+           */
+          y1: clampIfStackedAsPercentage(y1, stackMode),
+          y0: clampIfStackedAsPercentage(y0, stackMode),
           initialY0,
           initialY1,
           mark,
@@ -154,6 +161,10 @@ export function formatStackedDataSeriesValues(
   });
 }
 
+function clampIfStackedAsPercentage(value: number, stackMode?: StackMode) {
+  return stackMode === StackMode.Percentage ? clamp(value, 0, 1) : value;
+}
+
 function getOffsetBasedOnStackMode(stackMode?: StackMode) {
   switch (stackMode) {
     case StackMode.Percentage:

src/utils/common.ts

@@ -126,6 +126,10 @@ export function compareByValueAsc(a: number | string, b: number | string): numbe
   return a > b ? 1 : -1;
 }
 
+export function clamp(value: number, lowerBound: number, upperBound: number) {
+  return minValueWithLowerLimit(value, upperBound, lowerBound);
+}
+
 /**
  * Return the minimum value between val1 and val2. The value is bounded from below by lowerLimit
  * @param val1 a numeric value