fix(legend): use custom legend type throughout vega-lite compile functions

Author: hydrosquall

src/compile/layer.ts

@@ -1,4 +1,4 @@
-import {Legend as VgLegend, NewSignal, SignalRef, Title as VgTitle} from 'vega';
+import {NewSignal, SignalRef, Title as VgTitle} from 'vega';
 import {array} from 'vega-util';
 import {Config} from '../config';
 import * as log from '../log';
@@ -13,6 +13,8 @@ import {parseLayerLayoutSize} from './layoutsize/parse';
 import {assembleLegends} from './legend/assemble';
 import {Model} from './model';
 import {assembleLayerSelectionMarks} from './selection/assemble';
+import {FullVgLegend as VgLegend} from './legend/component';
+
 import {UnitModel} from './unit';
 
 export class LayerModel extends Model {

src/compile/legend/assemble.ts

@@ -1,10 +1,10 @@
-import {Legend as VgLegend, LegendEncode} from 'vega';
+import {LegendEncode} from 'vega';
 import {Config} from '../../config';
 import {LEGEND_SCALE_CHANNELS} from '../../legend';
 import {keys, replaceAll, stringify, vals} from '../../util';
 import {isSignalRef, VgEncodeChannel, VgValueRef} from '../../vega.schema';
 import {Model} from '../model';
-import {LegendComponent} from './component';
+import {FullVgLegend as VgLegend, LegendComponent} from './component';
 import {mergeLegendComponent} from './parse';
 
 function setLegendEncode(

src/compile/legend/component.ts

@@ -1,10 +1,24 @@
-import {Legend as VgLegend} from 'vega';
+import {Legend as VgLegend, LegendType} from 'vega';
 import {NonPositionScaleChannel} from '../../channel';
 import {COMMON_LEGEND_PROPERTY_INDEX, LegendInternal} from '../../legend';
 import {Flag, keys} from '../../util';
 import {Split} from '../split';
 
-export type LegendComponentProps = VgLegend & {
+/** Update LegendType to support a third value (discrete), which is needed for discrete gradient legends
+ * https://github.com/vega/vega/blob/main/packages/vega-parser/src/parsers/legend.js */
+export type FullLegendType = LegendType | 'discrete';
+
+/** Update LegendType to support a third value (discrete), which is needed for discrete gradient legends
+ * https://github.com/vega/vega/blob/main/packages/vega-parser/src/parsers/legend.js */
+export type FullVgLegend = Omit<VgLegend, 'type'> & {
+  /**
+   * The type of legend to include. One of `"symbol"` for discrete symbol legends, `"gradient"` for a continuous color gradient, or `"discrete"` for a discrete color gradient.
+   * If gradient is used only the fill, stroke, and length scale parameters are considered. If unspecified, the type will be inferred based on the scale parameters used and their backing scale types.
+   * TODO: Remove FullLegendType override after base type in VgLegend is updated */
+  type?: FullLegendType;
+};
+
+export type LegendComponentProps = FullVgLegend & {
   labelExpr?: string;
   selections?: string[];
   disable?: boolean;
@@ -29,7 +43,7 @@ const LEGEND_COMPONENT_PROPERTY_INDEX: Flag<keyof LegendComponentProps> = {
 
 export const LEGEND_COMPONENT_PROPERTIES = keys(LEGEND_COMPONENT_PROPERTY_INDEX);
 
-export class LegendComponent extends Split<LegendComponentProps> {}
+export class LegendComponent extends Split<LegendComponentProps> { }
 
 export type LegendComponentIndex = Partial<Record<NonPositionScaleChannel, LegendComponent>>;
 

src/compile/legend/encode.ts

@@ -1,4 +1,4 @@
-import {ColorValueRef, EncodeEntry, Gradient, LegendEncode, LegendType, SignalRef, SymbolEncodeEntry} from 'vega';
+import {ColorValueRef, EncodeEntry, Gradient, LegendEncode, SignalRef, SymbolEncodeEntry} from 'vega';
 import {array, isArray, stringValue} from 'vega-util';
 import {COLOR, NonPositionScaleChannel, OPACITY} from '../../channel';
 import {
@@ -19,14 +19,14 @@ import {formatCustomType, isCustomFormatType} from '../format';
 import * as mixins from '../mark/encode';
 import {STORE} from '../selection';
 import {UnitModel} from '../unit';
-import {LegendComponent} from './component';
+import {LegendComponent, FullLegendType} from './component';
 
 export interface LegendEncodeParams {
   fieldOrDatumDef: TypedFieldDef<string> | DatumDef;
   model: UnitModel;
   channel: NonPositionScaleChannel;
   legendCmpt: LegendComponent;
-  legendType: LegendType;
+  legendType: FullLegendType;
 }
 
 export const legendEncodeRules: {

src/compile/model.ts

@@ -1,7 +1,6 @@
 import {
   AnchorValue,
   Axis as VgAxis,
-  Legend as VgLegend,
   NewSignal,
   Projection as VgProjection,
   Signal,
@@ -56,7 +55,7 @@ import {
   LayoutSizeType
 } from './layoutsize/component';
 import {assembleLegends} from './legend/assemble';
-import {LegendComponentIndex} from './legend/component';
+import {LegendComponentIndex, FullVgLegend as VgLegend} from './legend/component';
 import {parseLegend} from './legend/parse';
 import {assembleProjections} from './projection/assemble';
 import {ProjectionComponent} from './projection/component';