[Lens] Fix reference line label rendering (elastic#151162)

## Summary

Fix elastic#151101

Refactored shared code between reference line and annotation rendering
to restore label rendering on Reference line.

The root issue was a refactoring of the code who only considered the
annotation configuration shape, which slightly differs from the
reference lines one, and in particular a stricter check for the label
configuration together with the assumption that an icon was always shown
in the annotation marker.

I've added few new unit tests to detect changes in the future in some
annotation logic, but it would be best to extend them in the future.

<img width="444" alt="Screenshot 2023-02-14 at 15 29 10"
src="https://user-images.githubusercontent.com/924948/218792072-a56ece78-07fd-4c0b-ab63-017590281b18.png">
<img width="451" alt="Screenshot 2023-02-14 at 15 29 17"
src="https://user-images.githubusercontent.com/924948/218792082-85630355-b003-4dea-86ca-3e90707c8293.png">

### Checklist

Delete any items that are not applicable to this PR.

- [ ] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)
- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [ ] Any UI touched in this PR is usable by keyboard only (learn more
about [keyboard accessibility](https://webaim.org/techniques/keyboard/))
- [ ] Any UI touched in this PR does not create any new axe failures
(run axe in browser:
[FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/),
[Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))
- [ ] If a plugin configuration key changed, check if it needs to be
allowlisted in the cloud and added to the [docker
list](https://github.com/elastic/kibana/blob/main/src/dev/build/tasks/os_packages/docker_generator/resources/base/bin/kibana-docker)
- [ ] This renders correctly on smaller devices using a responsive
layout. (You can test this [in your
browser](https://www.browserstack.com/guide/responsive-testing-on-local-server))
- [ ] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)

### Risk Matrix

Delete this section if it is not applicable to this PR.

Before closing this PR, invite QA, stakeholders, and other developers to
identify risks that should be tested prior to the change/feature
release.

When forming the risk matrix, consider some of the following examples
and how they may potentially impact the change:

| Risk | Probability | Severity | Mitigation/Notes |

|---------------------------|-------------|----------|-------------------------|
| Multiple Spaces&mdash;unexpected behavior in non-default Kibana Space.
| Low | High | Integration tests will verify that all features are still
supported in non-default Kibana Space and when user switches between
spaces. |
| Multiple nodes&mdash;Elasticsearch polling might have race conditions
when multiple Kibana nodes are polling for the same tasks. | High | Low
| Tasks are idempotent, so executing them multiple times will not result
in logical error, but will degrade performance. To test for this case we
add plenty of unit tests around this logic and document manual testing
procedure. |
| Code should gracefully handle cases when feature X or plugin Y are
disabled. | Medium | High | Unit tests will verify that any feature flag
or plugin combination still results in our service operational. |
| [See more potential risk
examples](https://github.com/elastic/kibana/blob/main/RISK_MATRIX.mdx) |

### For maintainers

- [ ] This was checked for breaking API changes and was [labeled
appropriately](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)

(cherry picked from commit 09033c8)

src/plugins/chart_expressions/expression_xy/common/expression_functions/reference_line.test.ts

@@ -16,6 +16,7 @@ describe('referenceLine', () => {
       value: 100,
       fill: 'above',
       position: 'bottom',
+      forAccessor: '',
     };
 
     const result = referenceLineFunction.fn(null, args, createMockExecutionContext());
@@ -47,6 +48,7 @@ describe('referenceLine', () => {
       color: '#fff',
       fill: 'below',
       textVisibility: true,
+      forAccessor: '',
     };
 
     const result = referenceLineFunction.fn(null, args, createMockExecutionContext());
@@ -71,6 +73,7 @@ describe('referenceLine', () => {
       value: 100,
       fill: 'none',
       position: 'bottom',
+      forAccessor: '',
     };
 
     const result = referenceLineFunction.fn(null, args, createMockExecutionContext());
@@ -96,6 +99,7 @@ describe('referenceLine', () => {
       textVisibility: true,
       fill: 'none',
       position: 'bottom',
+      forAccessor: '',
     };
 
     const result = referenceLineFunction.fn(null, args, createMockExecutionContext());
@@ -123,6 +127,7 @@ describe('referenceLine', () => {
         textVisibility,
         fill: 'none',
         position: 'bottom',
+        forAccessor: '',
       };
 
       const result = referenceLineFunction.fn(null, args, createMockExecutionContext());

src/plugins/chart_expressions/expression_xy/common/expression_functions/reference_line.ts

@@ -105,6 +105,11 @@ export const referenceLineFunction: ReferenceLineFn = {
       default: FillStyles.NONE,
       strict: true,
     },
+    forAccessor: {
+      types: ['string'],
+      help: '',
+      default: '',
+    },
   },
   fn(table, args) {
     const textVisibility =

src/plugins/chart_expressions/expression_xy/common/types/expression_functions.ts

@@ -329,8 +329,7 @@ export type ExtendedAnnotationLayerConfigResult = ExtendedAnnotationLayerArgs &
   layerType: typeof LayerTypes.ANNOTATIONS;
 };
 
-export interface ReferenceLineArgs
-  extends Omit<ReferenceLineDecorationConfig, 'forAccessor' | 'fill'> {
+export interface ReferenceLineArgs extends Omit<ReferenceLineDecorationConfig, 'fill'> {
   name?: string;
   value: number;
   fill: FillStyle;
@@ -365,6 +364,7 @@ export interface ReferenceLineConfigResult {
   type: typeof REFERENCE_LINE;
   layerType: typeof LayerTypes.REFERENCELINE;
   lineLength: number;
+  columnToLabel?: string;
   decorations: [ExtendedReferenceLineDecorationConfig];
 }
 

src/plugins/chart_expressions/expression_xy/public/components/reference_lines/reference_line.tsx

@@ -35,22 +35,27 @@ export const ReferenceLine: FC<ReferenceLineProps> = ({
 }) => {
   const {
     decorations: [decorationConfig],
+    columnToLabel,
   } = layer;
 
   if (!decorationConfig) {
     return null;
   }
 
   const { value } = decorationConfig;
+  const columnToLabelMap: Record<string, string> = columnToLabel ? JSON.parse(columnToLabel) : {};
 
   const axisGroup = getAxisGroupForReferenceLine(axesConfiguration, decorationConfig, isHorizontal);
 
   const formatter = axisGroup?.formatter || xAxisFormatter;
   const id = `${layer.layerId}-${value}`;
+  const name = decorationConfig.textVisibility
+    ? columnToLabelMap[decorationConfig.forAccessor]
+    : undefined;
 
   return (
     <ReferenceLineAnnotations
-      config={{ id, ...decorationConfig, nextValue, axisGroup }}
+      config={{ id, ...decorationConfig, name, nextValue, axisGroup }}
       paddingMap={paddingMap}
       axesMap={yAxesMap}
       formatter={formatter}

src/plugins/chart_expressions/expression_xy/public/components/reference_lines/reference_line_annotations.tsx

@@ -75,7 +75,7 @@ export const ReferenceLineAnnotations: FC<Props> = ({
   paddingMap,
   isHorizontal,
 }) => {
-  const { id, axisGroup, iconPosition, name, textVisibility, value, fill, color } = config;
+  const { id, axisGroup, iconPosition, name, value, fill, color } = config;
 
   const defaultColor = euiLightVars.euiColorDarkShade;
   // get the position for vertical chart
@@ -85,18 +85,9 @@ export const ReferenceLineAnnotations: FC<Props> = ({
     getOriginalAxisPosition(axisGroup?.position ?? Position.Bottom, isHorizontal)
   );
   // the padding map is built for vertical chart
-  const hasReducedPadding = paddingMap[markerPositionVertical] === LINES_MARKER_SIZE;
+  const isTextOnlyMarker = paddingMap[markerPositionVertical] === LINES_MARKER_SIZE;
 
-  const props = getLineAnnotationProps(
-    config,
-    {
-      markerLabel: name,
-      markerBodyLabel: textVisibility && !hasReducedPadding ? name : undefined,
-    },
-    axesMap,
-    paddingMap,
-    isHorizontal
-  );
+  const props = getLineAnnotationProps(config, name, axesMap, isHorizontal, isTextOnlyMarker);
 
   const sharedStyle = getSharedStyle(config);
 

src/plugins/chart_expressions/expression_xy/public/components/reference_lines/reference_lines.test.tsx

@@ -536,6 +536,7 @@ describe('ReferenceLines', () => {
                 lineStyle: 'solid',
                 fill,
                 value,
+                forAccessor: '',
               }),
             ]}
           />
@@ -576,6 +577,7 @@ describe('ReferenceLines', () => {
                 lineStyle: 'solid',
                 fill,
                 value,
+                forAccessor: '',
               }),
             ]}
           />
@@ -617,12 +619,14 @@ describe('ReferenceLines', () => {
                 lineStyle: 'solid',
                 fill,
                 value,
+                forAccessor: '',
               }),
               createReferenceLine(layerPrefix, 10, {
                 position,
                 lineStyle: 'solid',
                 fill,
                 value,
+                forAccessor: '',
               }),
             ]}
           />
@@ -667,12 +671,14 @@ describe('ReferenceLines', () => {
                 lineStyle: 'solid',
                 fill,
                 value,
+                forAccessor: '',
               }),
               createReferenceLine(layerPrefix, 10, {
                 position: 'bottom',
                 lineStyle: 'solid',
                 fill,
                 value,
+                forAccessor: '',
               }),
             ]}
           />
@@ -720,12 +726,14 @@ describe('ReferenceLines', () => {
                 lineStyle: 'solid',
                 fill: 'above',
                 value: value1,
+                forAccessor: '',
               }),
               createReferenceLine(layerPrefix, 10, {
                 position,
                 lineStyle: 'solid',
                 fill: 'below',
                 value: value2,
+                forAccessor: '',
               }),
             ]}
           />

src/plugins/chart_expressions/expression_xy/public/components/reference_lines/utils.test.tsx

@@ -7,8 +7,11 @@
  */
 
 import { AxisTypeId, computeInputCombinations, PosType } from './_mocks';
-import { computeChartMargins } from './utils';
-import { AxisConfiguration } from '../../helpers';
+import { computeChartMargins, getLineAnnotationProps } from './utils';
+import { AxesMap, AxisConfiguration, Marker, MarkerBody } from '../../helpers';
+import { ReferenceLineAnnotationConfig } from './reference_line_annotations';
+import { Position } from '@elastic/charts';
+import React from 'react';
 
 describe('reference lines helpers', () => {
   describe('computeChartMargins', () => {
@@ -36,4 +39,122 @@ describe('reference lines helpers', () => {
       }
     );
   });
+
+  describe('getLineAnnotationProps', () => {
+    function getAxesMap({ left, right }: Partial<AxesMap> = {}): AxesMap {
+      return {
+        left: { groupId: 'yLeft', position: Position.Left, series: [], ...left },
+        right: { groupId: 'yRight', position: Position.Right, series: [], ...right },
+      };
+    }
+    function getConfig(
+      customPartialConfig: Partial<ReferenceLineAnnotationConfig> = {}
+    ): ReferenceLineAnnotationConfig {
+      return {
+        id: 'id',
+        value: 3,
+        lineWidth: 5,
+        textVisibility: false,
+        iconPosition: 'auto',
+        axisGroup: getAxesMap().left,
+        ...customPartialConfig,
+      };
+    }
+
+    it('should render only the line with no marker', () => {
+      const config = getConfig();
+      expect(getLineAnnotationProps(config, 'myLabel', getAxesMap(), false, false)).toEqual(
+        expect.objectContaining({
+          groupId: 'yLeft',
+          markerPosition: Position.Left,
+          marker: (
+            <Marker
+              config={config}
+              label={'myLabel'}
+              isHorizontal={false}
+              hasReducedPadding={false}
+            />
+          ),
+          markerBody: <MarkerBody label={undefined} isHorizontal={false} />,
+        })
+      );
+    });
+    it('should render an icon marker', () => {
+      const config = getConfig({ icon: 'triangle' });
+      expect(getLineAnnotationProps(config, 'myLabel', getAxesMap(), false, false)).toEqual(
+        expect.objectContaining({
+          groupId: 'yLeft',
+          markerPosition: Position.Left,
+          marker: (
+            <Marker
+              config={config}
+              label={'myLabel'}
+              isHorizontal={false}
+              hasReducedPadding={false}
+            />
+          ),
+          markerBody: <MarkerBody label={undefined} isHorizontal={false} />,
+        })
+      );
+    });
+    it('should render only the label', () => {
+      const config = getConfig({ textVisibility: true });
+      expect(getLineAnnotationProps(config, 'myLabel', getAxesMap(), false, true)).toEqual(
+        expect.objectContaining({
+          groupId: 'yLeft',
+          markerPosition: Position.Left,
+          marker: (
+            <Marker
+              config={config}
+              label={'myLabel'}
+              isHorizontal={false}
+              hasReducedPadding={true}
+            />
+          ),
+          markerBody: <MarkerBody label={undefined} isHorizontal={false} />,
+        })
+      );
+    });
+    it('should render both icon and text', () => {
+      const config = getConfig({ icon: 'triangle', textVisibility: true });
+      expect(getLineAnnotationProps(config, 'myLabel', getAxesMap(), false, false)).toEqual(
+        expect.objectContaining({
+          groupId: 'yLeft',
+          markerPosition: Position.Left,
+          marker: (
+            <Marker
+              config={config}
+              label={'myLabel'}
+              isHorizontal={false}
+              hasReducedPadding={false}
+            />
+          ),
+          markerBody: <MarkerBody label={'myLabel'} isHorizontal={false} />,
+        })
+      );
+    });
+
+    it('should handle marker rotated label', () => {
+      const config = getConfig({
+        icon: 'triangle',
+        textVisibility: true,
+        axisGroup: { groupId: 'x', position: Position.Bottom, series: [] },
+      });
+      expect(getLineAnnotationProps(config, 'myLabel', getAxesMap(), false, false)).toEqual(
+        expect.objectContaining({
+          groupId: 'x',
+          markerPosition: Position.Top,
+          marker: (
+            <Marker
+              config={config}
+              label={'myLabel'}
+              isHorizontal={true}
+              hasReducedPadding={false}
+            />
+          ),
+          markerBody: <MarkerBody label={'myLabel'} isHorizontal={true} />,
+        })
+      );
+    });
+  });
 });

src/plugins/chart_expressions/expression_xy/public/components/reference_lines/utils.tsx

@@ -21,15 +21,14 @@ import {
 import { FillStyles } from '../../../common/constants';
 import {
   GroupsConfiguration,
-  LINES_MARKER_SIZE,
   mapVerticalToHorizontalPlacement,
   Marker,
   MarkerBody,
   getAxisPosition,
   getOriginalAxisPosition,
   AxesMap,
 } from '../../helpers';
-import { ReferenceLineAnnotationConfig } from './reference_line_annotations';
+import type { ReferenceLineAnnotationConfig } from './reference_line_annotations';
 
 // if there's just one axis, put it on the other one
 // otherwise use the same axis
@@ -84,10 +83,10 @@ export const getSharedStyle = (config: ReferenceLineAnnotationConfig) => ({
 
 export const getLineAnnotationProps = (
   config: ReferenceLineAnnotationConfig,
-  labels: { markerLabel?: string; markerBodyLabel?: string },
+  label: string | undefined,
   axesMap: AxesMap,
-  paddingMap: Partial<Record<Position, number>>,
-  isHorizontal: boolean
+  isHorizontal: boolean,
+  isTextOnlyMarker: boolean
 ) => {
   // get the position for vertical chart
   const markerPositionVertical = getBaseIconPlacement(
@@ -96,27 +95,27 @@ export const getLineAnnotationProps = (
     getOriginalAxisPosition(config.axisGroup?.position ?? Position.Bottom, isHorizontal)
   );
 
-  // the padding map is built for vertical chart
-  const hasReducedPadding = paddingMap[markerPositionVertical] === LINES_MARKER_SIZE;
-
   const markerPosition = isHorizontal
     ? mapVerticalToHorizontalPlacement(markerPositionVertical)
     : markerPositionVertical;
 
+  const isMarkerLabelHorizontal =
+    markerPosition === Position.Bottom || markerPosition === Position.Top;
+
   return {
     groupId: config.axisGroup?.groupId || 'bottom',
     marker: (
       <Marker
         config={config}
-        label={labels.markerLabel}
-        isHorizontal={isHorizontal}
-        hasReducedPadding={hasReducedPadding}
+        label={label}
+        isHorizontal={isMarkerLabelHorizontal}
+        hasReducedPadding={isTextOnlyMarker}
       />
     ),
     markerBody: (
       <MarkerBody
-        label={labels.markerBodyLabel}
-        isHorizontal={markerPosition === Position.Bottom || markerPosition === Position.Top}
+        label={config.textVisibility && !isTextOnlyMarker ? label : undefined}
+        isHorizontal={isMarkerLabelHorizontal}
       />
     ),
     // rotate the position if required