Allow to sort reverse

cf #698

umap/static/umap/js/umap.core.js

@@ -202,7 +202,12 @@ L.Util.sortFeatures = (features, sortKey) => {
   const sortKeys = (sortKey || 'name').split(',')
 
   const sort = (a, b, i) => {
-    const sortKey = sortKeys[i]
+    let sortKey = sortKeys[i],
+      reverse = 1
+    if (sortKey[0] === '-') {
+      reverse = -1
+      sortKey = sortKey.substring(1)
+    }
     let score
     const valA = a.properties[sortKey] || ''
     const valB = b.properties[sortKey] || ''
@@ -221,7 +226,7 @@ L.Util.sortFeatures = (features, sortKey) => {
         })
     }
     if (score === 0 && sortKeys[i + 1]) return sort(a, b, i + 1)
-    return score
+    return score * reverse
   }
 
   features.sort((a, b) => {

umap/static/umap/test/Util.js

@@ -446,4 +446,55 @@ describe('L.Util', function () {
       assert.ok(L.Util.usableOption({ key: null }, 'key'))
     })
   })
+
+  describe("#sortFeatures()", function () {
+    let feat1, feat2, feat3
+    before(function () {
+      feat1 = {properties: {}}
+      feat2 = {properties: {}}
+      feat3 = {properties: {}}
+    })
+    it('should sort feature from custom key', function () {
+      feat1.properties.mykey = "13. foo"
+      feat2.properties.mykey = "7. foo"
+      feat3.properties.mykey = "111. foo"
+      let features = L.Util.sortFeatures([feat1, feat2, feat3], "mykey")
+      assert.equal(features[0], feat2)
+      assert.equal(features[1], feat1)
+      assert.equal(features[2], feat3)
+    })
+    it('should sort feature from multiple keys', function () {
+      feat1.properties.mykey = "13. foo"
+      feat2.properties.mykey = "111. foo"
+      feat3.properties.mykey = "111. foo"
+      feat1.properties.otherkey = "C"
+      feat2.properties.otherkey = "B"
+      feat3.properties.otherkey = "A"
+      let features = L.Util.sortFeatures([feat1, feat2, feat3], "mykey,otherkey")
+      assert.equal(features[0], feat1)
+      assert.equal(features[1], feat3)
+      assert.equal(features[2], feat2)
+    })
+    it('should sort feature from custom key reverse', function () {
+      feat1.properties.mykey = "13. foo"
+      feat2.properties.mykey = "7. foo"
+      feat3.properties.mykey = "111. foo"
+      let features = L.Util.sortFeatures([feat1, feat2, feat3], "-mykey")
+      assert.equal(features[0], feat3)
+      assert.equal(features[1], feat1)
+      assert.equal(features[2], feat2)
+    })
+    it('should sort feature from multiple keys with reverse', function () {
+      feat1.properties.mykey = "13. foo"
+      feat2.properties.mykey = "111. foo"
+      feat3.properties.mykey = "111. foo"
+      feat1.properties.otherkey = "C"
+      feat2.properties.otherkey = "B"
+      feat3.properties.otherkey = "A"
+      let features = L.Util.sortFeatures([feat1, feat2, feat3], "mykey,-otherkey")
+      assert.equal(features[0], feat1)
+      assert.equal(features[1], feat2)
+      assert.equal(features[2], feat3)
+    })
+  })
 })