🐛 (explorer) remove mapTargetTime=0 from grapher config

explorer/ExplorerProgram.ts

@@ -18,8 +18,8 @@ import {
     PromiseCache,
     SerializedGridProgram,
     trimObject,
-    mergeGrapherConfigs,
     merge,
+    isEmpty,
 } from "@ourworldindata/utils"
 import {
     CellDef,
@@ -409,6 +409,20 @@ export class ExplorerProgram extends GridProgram {
             ]
         }
 
+        // because explorers used to ignore mapTargetTime=0, authors have been
+        // exploiting this behaviour to show the latest data on the map.
+        // this would be equivalent to not setting a mapTargetTime, but
+        // removing a column is more work than resetting all values,
+        // which is why authors have been relying on this behaviour.
+        // ideally, we'd clean up all explorers by removing all instances of
+        // mapTargetTime=0 and then remove this code, but realistically there
+        // is no rush since it's very unlikely that we'll ever create an explorer
+        // that actually wants to show the year 0 on a map by default
+        if (mergedConfig.map?.time === 0) {
+            delete mergedConfig.map.time
+            if (isEmpty(mergedConfig.map)) delete mergedConfig.map
+        }
+
         return mergedConfig
     }