move tickFormat function detection

Author: mbostock

src/legends/swatches.js

@@ -86,7 +86,7 @@ function legendItems(scale, options = {}, swatch) {
   } = options;
   const context = createContext(options);
   className = maybeClassName(className);
-  if (typeof tickFormat !== "function") tickFormat = inferTickFormat(scale.scale, scale.domain, undefined, tickFormat);
+  tickFormat = inferTickFormat(scale.scale, scale.domain, undefined, tickFormat);
 
   const swatches = create("div", context).attr(
     "class",

src/marks/axis.js

@@ -628,9 +628,7 @@ function inferTickCount(scale, tickSpacing) {
 }
 
 function inferTextChannel(scale, data, ticks, tickFormat, anchor) {
-  return {
-    value: typeof tickFormat === "function" ? tickFormat : inferTickFormat(scale, data, ticks, tickFormat, anchor)
-  };
+  return {value: inferTickFormat(scale, data, ticks, tickFormat, anchor)};
 }
 
 // D3’s ordinal scales simply use toString by default, but if the ordinal scale
@@ -640,7 +638,9 @@ function inferTextChannel(scale, data, ticks, tickFormat, anchor) {
 // possible, or the default ISO format (2014-01-26). TODO We need a better way
 // to infer whether the ordinal scale is UTC or local time.
 export function inferTickFormat(scale, data, ticks, tickFormat, anchor) {
-  return tickFormat === undefined && data && isTemporal(data)
+  return typeof tickFormat === "function"
+    ? tickFormat
+    : tickFormat === undefined && data && isTemporal(data)
     ? inferTimeFormat(data, anchor) ?? formatDefault
     : scale.tickFormat
     ? scale.tickFormat(typeof ticks === "number" ? ticks : null, tickFormat)