on preset change: don't drop tags if ∃ a matching field in the new preset

closes #9341
closes #9104

CHANGELOG.md

@@ -46,6 +46,7 @@ _Breaking developer changes, which may affect downstream projects or sites that
 #### :bug: Bugfixes
 * Fix selection of best background source when starting on a zoomed-out view ([#9325])
 * Fix leaking of localized strings in combo fields when taginfo service is unavailable ([#9342])
+* Keep tags when changing presets if the new preset has a field for it ([#9341], [#9104])
 #### :rocket: Presets
 * Support tagging schema v5 ([#9320]):
   * Add new field type `colour` ([schema-builder#38], [#8782])
@@ -56,9 +57,11 @@ _Breaking developer changes, which may affect downstream projects or sites that
 * Make settings like CDN and API urls configurable in a central config file (`/config/is.js`)
 
 [#8105]: https://github.com/openstreetmap/iD/issues/8105
+[#9104]: https://github.com/openstreetmap/iD/issues/9104
 [#9294]: https://github.com/openstreetmap/iD/issues/9294
 [#9320]: https://github.com/openstreetmap/iD/pull/9320
 [#9325]: https://github.com/openstreetmap/iD/issues/9325
+[#9341]: https://github.com/openstreetmap/iD/issues/9341
 [#9342]: https://github.com/openstreetmap/iD/issues/9342
 [schema-builder#38]: https://github.com/ideditor/schema-builder/pull/38
 

modules/actions/change_preset.js

@@ -5,7 +5,18 @@ export function actionChangePreset(entityID, oldPreset, newPreset, skipFieldDefa
         var tags = entity.tags;
 
         // preserve tags that the new preset might care about, if any
-        if (oldPreset) tags = oldPreset.unsetTags(tags, geometry, newPreset && newPreset.addTags ? Object.keys(newPreset.addTags) : null);
+        var preserveKeys;
+        if (newPreset) {
+            preserveKeys = [];
+            if (newPreset.addTags) {
+                preserveKeys = preserveKeys.concat(Object.keys(newPreset.addTags));
+            }
+            newPreset.fields().concat(newPreset.moreFields())
+                .filter(f => f.matchGeometry(geometry))
+                .map(f => f.key).filter(Boolean)
+                .forEach(key => preserveKeys.push(key));
+        }
+        if (oldPreset) tags = oldPreset.unsetTags(tags, geometry, preserveKeys);
         if (newPreset) tags = newPreset.setTags(tags, geometry, skipFieldDefaults);
 
         return graph.replace(entity.update({tags: tags}));

modules/presets/preset.js

@@ -226,7 +226,9 @@ export function presetPreset(presetID, preset, addable, allFields, allPresets) {
 
     if (geometry && !skipFieldDefaults) {
       _this.fields().forEach(field => {
-        if (field.matchGeometry(geometry) && field.key && field.default === tags[field.key]) {
+        if (field.matchGeometry(geometry) && field.key &&
+            field.default === tags[field.key] &&
+            ignoringKeys.indexOf(field.key) !== -1) {
           delete tags[field.key];
         }
       });