From 0ee8427386e612b00db2c7dded4b922eaf0bf605 Mon Sep 17 00:00:00 2001
From: "Grot (@grafanabot)" <43478413+grafanabot@users.noreply.github.com>
Date: Thu, 5 Nov 2020 15:29:41 +0530
Subject: [PATCH] Units: added support to handle negative fractional numbers.
 (#28849) (#28851)

(cherry picked from commit abe96f4f898d72f868e3d04d6f21426330cfb188)

Co-authored-by: Marcus Andersson <marcus.andersson@grafana.com>
---
 .../src/field/displayProcessor.test.ts        | 20 ++++++++++++++++++-
 .../src/field/displayProcessor.ts             |  2 +-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/packages/grafana-data/src/field/displayProcessor.test.ts b/packages/grafana-data/src/field/displayProcessor.test.ts
index 9d7c4b5f998..7876087832b 100644
--- a/packages/grafana-data/src/field/displayProcessor.test.ts
+++ b/packages/grafana-data/src/field/displayProcessor.test.ts
@@ -1,4 +1,4 @@
-import { getDisplayProcessor, getRawDisplayProcessor } from './displayProcessor';
+import { getDecimalsForValue, getDisplayProcessor, getRawDisplayProcessor } from './displayProcessor';
 import { DisplayProcessor, DisplayValue } from '../types/displayValue';
 import { MappingType, ValueMapping } from '../types/valueMapping';
 import { FieldConfig, FieldType, ThresholdsMode } from '../types';
@@ -329,3 +329,21 @@ describe('getRawDisplayProcessor', () => {
     expect(result).toEqual({ text: expected, numeric: null });
   });
 });
+
+describe('getDecimalsForValue', () => {
+  it.each`
+    value                   | expected
+    ${0}                    | ${0}
+    ${13.37}                | ${0}
+    ${-13.37}               | ${0}
+    ${12679.3712345811212}  | ${0}
+    ${-12679.3712345811212} | ${0}
+    ${0.3712345}            | ${2}
+    ${-0.37123458}          | ${2}
+    ${-0.04671994403853774} | ${3}
+    ${0.04671994403853774}  | ${3}
+  `('should return correct suggested decimal count', ({ value, expected }) => {
+    const result = getDecimalsForValue(value);
+    expect(result.decimals).toEqual(expected);
+  });
+});
diff --git a/packages/grafana-data/src/field/displayProcessor.ts b/packages/grafana-data/src/field/displayProcessor.ts
index 66705096ebf..e7c5c45cf54 100644
--- a/packages/grafana-data/src/field/displayProcessor.ts
+++ b/packages/grafana-data/src/field/displayProcessor.ts
@@ -143,7 +143,7 @@ export function getDecimalsForValue(value: number, decimalOverride?: DecimalCoun
     return { decimals: decimalOverride, scaledDecimals: null };
   }
 
-  let dec = -Math.floor(Math.log(value) / Math.LN10) + 1;
+  let dec = -Math.floor(Math.log(Math.abs(value)) / Math.LN10) + 1;
   const magn = Math.pow(10, -dec);
   const norm = value / magn; // norm is between 1.0 and 10.0
   let size;