Make sure a LineString has at least two points

According to the GeoJSON specification [1]:

> For type "LineString", the "coordinates" member is an array of two or
> more positions.

Note that the same doesn't seem to apply to a MultiPoint [2]:

> For type "MultiPoint", the "coordinates" member is an array of
> positions.

[1] https://datatracker.ietf.org/doc/html/rfc7946#section-3.1.4
[2] https://datatracker.ietf.org/doc/html/rfc7946#section-3.1.3

app/models/concerns/geojson_format_validator.rb

@@ -79,8 +79,10 @@ class GeojsonFormatValidator < ActiveModel::EachValidator
       case geometry["type"]
       when "Point"
         valid_wgs84_coordinates?(coordinates)
-      when "LineString", "MultiPoint"
+      when "LineString"
-        coordinates.all? { |coordinates| valid_wgs84_coordinates?(coordinates) }
+        coordinates.many? && valid_coordinates_array?(coordinates)
+      when "MultiPoint"
+        valid_coordinates_array?(coordinates)
       when "Polygon", "MultiLineString"
         valid_polygon_coordinates?(coordinates)
       when "MultiPolygon"
@@ -99,9 +101,13 @@ class GeojsonFormatValidator < ActiveModel::EachValidator
       (-180.0..180.0).include?(longitude) && (-90.0..90.0).include?(latitude)
     end
 
+    def valid_coordinates_array?(coordinates_array)
+      coordinates_array.all? { |coordinates| valid_wgs84_coordinates?(coordinates) }
+    end
+
     def valid_polygon_coordinates?(polygon_coordinates)
-      polygon_coordinates.all? do |ring|
+      polygon_coordinates.all? do |ring_coordinates|
-        ring.all? { |coordinates| valid_wgs84_coordinates?(coordinates) }
+        valid_coordinates_array?(ring_coordinates)
       end
     end
 end

spec/models/geojson_format_validator_spec.rb

@@ -122,16 +122,6 @@ describe GeojsonFormatValidator do
       expect(record).not_to be_valid
     end
 
-    it "is valid with a two-dimensional array including only one point" do
-      record.geojson = '{ "type": "LineString", "coordinates": [[1.23, 4.56]] }'
-
-      expect(record).to be_valid
-
-      record.geojson = '{ "type": "MultiPoint", "coordinates": [[1.23, 4.56]] }'
-
-      expect(record).to be_valid
-    end
-
     it "is not valid when some coordinates are invalid" do
       record.geojson = '{ "type": "LineString", "coordinates": [[1.23, 4.56], [180.01, 4.56]] }'
 
@@ -153,6 +143,22 @@ describe GeojsonFormatValidator do
     end
   end
 
+  context "LineString geometry" do
+    it "is not valid with only one point" do
+      record.geojson = '{ "type": "LineString", "coordinates": [[1.23, 4.56]] }'
+
+      expect(record).not_to be_valid
+    end
+  end
+
+  context "MultiPoint geometry" do
+    it "is valid with only one point" do
+      record.geojson = '{ "type": "MultiPoint", "coordinates": [[1.23, 4.56]] }'
+
+      expect(record).to be_valid
+    end
+  end
+
   context "GeometryCollection" do
     it "is not valid if it doesn't contain geometries" do
       record.geojson = '{ "type": "GeometryCollection" }'