performance: Make _referencing_ways actually lazy

Logic/SimpleMetaTagger.ts

@@ -80,20 +80,25 @@ export class ReferencingWaysMetaTagger extends SimpleMetaTagger {
                 if (!id.startsWith("node/")) {
                     return false
                 }
-                console.trace("Downloading referencing ways for", feature.properties.id)
-                OsmObject.DownloadReferencingWays(id).then((referencingWays) => {
-                    const currentTagsSource = state.allElements?.getEventSourceById(id) ?? []
-                    const wayIds = referencingWays.map((w) => "way/" + w.id)
-                    wayIds.sort()
-                    const wayIdsStr = wayIds.join(";")
-                    if (
-                        wayIdsStr !== "" &&
-                        currentTagsSource.data["_referencing_ways"] !== wayIdsStr
-                    ) {
-                        currentTagsSource.data["_referencing_ways"] = wayIdsStr
-                        currentTagsSource.ping()
+
+                const currentTagsSource = state.allElements?.getEventSourceById(id)
+                if (currentTagsSource === undefined) {
+                    return
+                }
+                Utils.AddLazyPropertyAsync(
+                    currentTagsSource.data,
+                    "_referencing_ways",
+                    async () => {
+                        const referencingWays = await OsmObject.DownloadReferencingWays(id)
+                        const wayIds = referencingWays.map((w) => "way/" + w.id)
+                        wayIds.sort()
+                        const wayIdsStr = wayIds.join(";")
+                        if (wayIdsStr !== "" && currentTagsSource.data[""] !== wayIdsStr) {
+                            currentTagsSource.data["_referencing_ways"] = wayIdsStr
+                            currentTagsSource.ping()
+                        }
                     }
-                })
+                )
 
                 return true
             }
@@ -282,16 +287,9 @@ export default class SimpleMetaTaggers {
                 },
             })
 
-            Object.defineProperty(feature.properties, "_surface:ha", {
-                enumerable: false,
-                configurable: true,
-                get: () => {
-                    const sqMeters = GeoOperations.surfaceAreaInSqMeters(feature)
-                    const sqMetersHa = "" + Math.floor(sqMeters / 1000) / 10
-                    delete feature.properties["_surface:ha"]
-                    feature.properties["_surface:ha"] = sqMetersHa
-                    return sqMetersHa
-                },
+            Utils.AddLazyProperty(feature.properties, "_surface:ha", () => {
+                const sqMeters = GeoOperations.surfaceAreaInSqMeters(feature)
+                return "" + Math.floor(sqMeters / 1000) / 10
             })
 
             return true
@@ -443,8 +441,6 @@ export default class SimpleMetaTaggers {
                     }
                 },
             })
-
-            const tagsSource = state.allElements.getEventSourceById(feature.properties.id)
         }
     )
     private static directionSimplified = new SimpleMetaTagger(

Utils.ts

@@ -300,6 +300,49 @@ In the case that MapComplete is pointed to the testing grounds, the edit will be
         return str.substr(0, l - 3) + "..."
     }
 
+    /**
+     * Adds a property to the given object, but the value will _only_ be calculated when it is actually requested
+     * @param object
+     * @param name
+     * @param init
+     * @constructor
+     */
+    public static AddLazyProperty(object: any, name: string, init: () => any) {
+        Object.defineProperty(object, name, {
+            enumerable: false,
+            configurable: true,
+            get: () => {
+                delete object[name]
+                object[name] = init()
+                return object[name]
+            },
+        })
+    }
+
+    /**
+     * Adds a property to the given object, but the value will _only_ be calculated when it is actually requested
+     */
+    public static AddLazyPropertyAsync(
+        object: any,
+        name: string,
+        init: () => Promise<any>,
+        whenDone?: () => void
+    ) {
+        Object.defineProperty(object, name, {
+            enumerable: false,
+            configurable: true,
+            get: () => {
+                init().then((r) => {
+                    delete object[name]
+                    object[name] = r
+                    if (whenDone) {
+                        whenDone()
+                    }
+                })
+            },
+        })
+    }
+
     public static FixedLength(str: string, l: number) {
         str = Utils.EllipsesAfter(str, l)
         while (str.length < l) {
@@ -1281,13 +1324,6 @@ In the case that MapComplete is pointed to the testing grounds, the edit will be
         return d
     }
 
-    private static colorDiff(
-        c0: { r: number; g: number; b: number },
-        c1: { r: number; g: number; b: number }
-    ) {
-        return Math.abs(c0.r - c1.r) + Math.abs(c0.g - c1.g) + Math.abs(c0.b - c1.b)
-    }
-
     static toIdRecord<T extends { id: string }>(ts: T[]): Record<string, T> {
         const result: Record<string, T> = {}
         for (const t of ts) {
@@ -1317,4 +1353,11 @@ In the case that MapComplete is pointed to the testing grounds, the edit will be
         // If the element has a parent, repeat the process for the parent element
         return Utils.findParentWithScrolling(element.parentElement)
     }
+
+    private static colorDiff(
+        c0: { r: number; g: number; b: number },
+        c1: { r: number; g: number; b: number }
+    ) {
+        return Math.abs(c0.r - c1.r) + Math.abs(c0.g - c1.g) + Math.abs(c0.b - c1.b)
+    }
 }