refactor: don't interpret numbers as truth values

src/compile/facet.ts

@@ -324,7 +324,7 @@ export class FacetModel extends ModelWithField {
       name,
       data,
       groupby,
-      ...(cross || fields.length
+      ...(cross || fields.length > 0
         ? {
             aggregate: {
               ...(cross ? {cross} : {}),

src/compile/mark/valueref.ts

@@ -443,7 +443,7 @@ export function tooltipForEncoding(
     }
   }
 
-  return keyValues.length ? {signal: `{${keyValues.join(', ')}}`} : undefined;
+  return keyValues.length > 0 ? {signal: `{${keyValues.join(', ')}}`} : undefined;
 }
 
 export function text(

src/compile/selection/assemble.ts

@@ -76,7 +76,7 @@ export function assembleTopLevelSignals(model: UnitModel, signals: Signal[]) {
     const name = selCmpt.name;
     const store = stringValue(name + STORE);
     const hasSg = signals.filter(s => s.name === name);
-    if (!hasSg.length) {
+    if (hasSg.length === 0) {
       const resolve = selCmpt.resolve === 'global' ? 'union' : selCmpt.resolve;
       const isMulti = selCmpt.type === 'multi' ? ', true)' : ')';
       signals.push({
@@ -99,7 +99,7 @@ export function assembleTopLevelSignals(model: UnitModel, signals: Signal[]) {
 
   if (hasSelections) {
     const hasUnit = signals.filter(s => s.name === 'unit');
-    if (!hasUnit.length) {
+    if (hasUnit.length === 0) {
       signals.unshift({
         name: 'unit',
         value: {},

src/compile/selection/transforms/legends.ts

@@ -59,7 +59,7 @@ const legendBindings: TransformCompiler = {
       const sgName = `${selName}_${prefix}`;
       const hasSignal = signals.filter(s => s.name === sgName);
 
-      if (!hasSignal.length) {
+      if (hasSignal.length === 0) {
         const events = stream.merge
           .map(markName(`${prefix}_symbols`))
           .concat(stream.merge.map(markName(`${prefix}_labels`)));
@@ -87,12 +87,12 @@ const legendBindings: TransformCompiler = {
     const valid = values.map(v => `${v} !== null`).join(' && ');
     const update = `${valid} ? {fields: ${fields}, values: [${values.join(', ')}]} : null`;
 
-    if (selCmpt.events && values.length) {
+    if (selCmpt.events && values.length > 0) {
       tuple.on.push({
         events: values.map(signal => ({signal})),
         update
       });
-    } else if (values.length) {
+    } else if (values.length > 0) {
       tuple.update = update;
       delete tuple.value;
       delete tuple.on;

src/compile/selection/transforms/project.ts

@@ -151,15 +151,15 @@ const project: TransformCompiler = {
       }
     }
 
-    if (keys(timeUnits).length) {
+    if (keys(timeUnits).length > 0) {
       proj.timeUnit = new TimeUnitNode(null, timeUnits);
     }
   },
 
   signals: (model, selCmpt, allSignals) => {
     const name = selCmpt.name + TUPLE_FIELDS;
     const hasSignal = allSignals.filter(s => s.name === name);
-    return hasSignal.length
+    return hasSignal.length > 0
       ? allSignals
       : allSignals.concat({
           name,

src/compile/selection/transforms/scales.ts

@@ -44,11 +44,11 @@ const scaleBindings: TransformCompiler = {
   },
 
   topLevelSignals: (model, selCmpt, signals) => {
-    const bound = selCmpt.scales.filter(proj => !signals.filter(s => s.name === proj.signals.data).length);
+    const bound = selCmpt.scales.filter(proj => signals.filter(s => s.name === proj.signals.data).length === 0);
 
     // Top-level signals are only needed for multiview displays and if this
     // view's top-level signals haven't already been generated.
-    if (!model.parent || isTopLevelLayer(model) || !bound.length) {
+    if (!model.parent || isTopLevelLayer(model) || bound.length === 0) {
       return signals;
     }
 

src/compositemark/errorbar.ts

@@ -375,7 +375,7 @@ export function errorBarParams<
       ...(outerSpec.transform || []),
       ...bins,
       ...timeUnits,
-      ...(!aggregate.length ? [] : [{aggregate, groupby}]),
+      ...(aggregate.length === 0 ? [] : [{aggregate, groupby}]),
       ...postAggregateCalculates
     ],
     groupby,

src/normalize/rangestep.ts

@@ -47,7 +47,7 @@ export class RangeStepNormalizer implements NonFacetUnitNormalizer<UnitSpecWithR
             ...encoding,
             [channel]: {
               ...defWithoutScale,
-              ...(keys(scaleWithoutRangeStep).length ? {scale: scaleWithoutRangeStep} : {})
+              ...(keys(scaleWithoutRangeStep).length > 0 ? {scale: scaleWithoutRangeStep} : {})
             }
           };
         }

src/transformextract.ts

@@ -14,7 +14,7 @@ class TransformExtractMapper extends SpecMapper<{config: Config}, GenericUnitSpe
         ...(oldTransforms ? oldTransforms : []),
         ...bins,
         ...timeUnits,
-        ...(!aggregate.length ? [] : [{aggregate, groupby}])
+        ...(aggregate.length === 0 ? [] : [{aggregate, groupby}])
       ];
 
       return {