Add mechanism for fields to support editing during multiselection (re: #7276)

Add `utilCombinedTags` method and use it for the raw tag editor as well as fields
Pass `entityIDs` array into fields instead of single `entity` object
Give field revertion its own path separate from `change`
Add multiselection editing to fields in files: access, address, check, combo, cycleway, input, maxspeed, textarea, and wikidata

modules/util/index.js

@@ -10,6 +10,7 @@ export { utilArrayUniqBy } from './array';
 
 export { utilAsyncMap } from './util';
 export { utilCleanTags } from './clean_tags';
+export { utilCombinedTags } from './util';
 export { utilDeepMemberSelector } from './util';
 export { utilDetect } from './detect';
 export { utilDisplayName } from './util';

modules/util/util.js

@@ -230,6 +230,93 @@ export function utilEntityRoot(entityType) {
 }
 
 
+// Returns a single object containing the tags of all the given entities.
+// Example:
+// {
+//   highway: 'service',
+//   service: 'parking_aisle'
+// }
+//           +
+// {
+//   highway: 'service',
+//   service: 'driveway',
+//   width: '3'
+// }
+//           =
+// {
+//   highway: 'service',
+//   service: [ 'driveway', 'parking_aisle' ],
+//   width: [ '3', undefined ]
+// }
+export function utilCombinedTags(entityIDs, graph) {
+
+    var tags = {};
+    var tagCounts = {};
+    var allKeys = new Set();
+
+    var entities = entityIDs.map(function(entityID) {
+        return graph.hasEntity(entityID);
+    }).filter(Boolean);
+
+    // gather the aggregate keys
+    entities.forEach(function(entity) {
+        var keys = Object.keys(entity.tags).filter(Boolean);
+        keys.forEach(function(key) {
+            allKeys.add(key);
+        });
+    });
+
+    entities.forEach(function(entity) {
+
+        allKeys.forEach(function(key) {
+
+            var value = entity.tags[key]; // purposely allow `undefined`
+
+            if (!tags.hasOwnProperty(key)) {
+                // first value, set as raw
+                tags[key] = value;
+            } else {
+                if (!Array.isArray(tags[key])) {
+                    if (tags[key] !== value) {
+                        // first alternate value, replace single value with array
+                        tags[key] = [tags[key], value];
+                    }
+                } else { // type is array
+                    if (tags[key].indexOf(value) === -1) {
+                        // subsequent alternate value, add to array
+                        tags[key].push(value);
+                    }
+                }
+            }
+
+            var tagHash = key + '=' + value;
+            if (!tagCounts[tagHash]) tagCounts[tagHash] = 0;
+            tagCounts[tagHash] += 1;
+        });
+    });
+
+    for (var key in tags) {
+        if (!Array.isArray(tags[key])) continue;
+
+        // sort values by frequency then alphabetically
+        tags[key] = tags[key].sort(function(val1, val2) {
+            var key = key; // capture
+            var count2 = tagCounts[key + '=' + val2];
+            var count1 = tagCounts[key + '=' + val1];
+            if (count2 !== count1) {
+                return count2 - count1;
+            }
+            if (val2 && val1) {
+                return val1.localeCompare(val2);
+            }
+            return val1 ? 1 : -1;
+        });
+    }
+
+    return tags;
+}
+
+
 export function utilStringQs(str) {
     return str.split('&').reduce(function(obj, pair){
         var parts = pair.split('=');