Handle null altitudes when reading positions

Author: Sokigo-TS

src/GeoJSON.Text.Test.Unit/GeoJSON.Text.Test.Unit.csproj

@@ -22,6 +22,7 @@
     <None Remove="Feature\GenericFeatureTests_Can_Deserialize_Typed_Point_Feature.json" />
     <None Remove="Feature\GenericFeatureTests_Can_Serialize_Typed_Point_Feature.json" />
     <None Remove="Geometry\LineStringTests_Can_Deserialize.json" />
+    <None Remove="Geometry\LineStringTests_Can_Deserialize_With_Altitude.json" />
     <None Remove="Geometry\LineStringTests_Can_Serialize.json" />
     <None Remove="Geometry\MultiLineStringTests_Can_Deserialize.json" />
     <None Remove="Geometry\MultiLineStringTests_Can_Serialize.json" />
@@ -76,6 +77,9 @@
   <ItemGroup>
     <ProjectReference Include="..\GeoJSON.Text\GeoJSON.Text.csproj" />
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Geometry\LineStringTests_Can_Deserialize_With_Altitude.json" />
+  </ItemGroup>
   <ItemGroup>
     <None Update="Feature\*.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>

src/GeoJSON.Text.Test.Unit/Geometry/LineStringTests.cs

@@ -83,6 +83,31 @@ public void Can_Deserialize()
             Assert.AreEqual(expectedLineString.Coordinates[0].Longitude, actualLineString.Coordinates[0].Longitude);
         }
 
+        [Test]
+        public void Can_Deserialize_With_Altitude()
+        {
+            var coordinates = new List<IPosition>
+            {
+                new Position(52.370725881211314, 4.889259338378906, 10.0),
+                new Position(52.3711451105601, 4.895267486572266, 10.5),
+                new Position(52.36931095278263, 4.892091751098633, null),
+                new Position(52.370725881211314, 4.889259338378906, 10.2)
+            };
+
+            var expectedLineString = new LineString(coordinates);
+
+            var json = GetExpectedJson();
+            var actualLineString = JsonSerializer.Deserialize<LineString>(json);
+
+            Assert.AreEqual(expectedLineString, actualLineString);
+
+            Assert.AreEqual(4, actualLineString.Coordinates.Count);
+            Assert.AreEqual(expectedLineString.Coordinates[0].Latitude, actualLineString.Coordinates[0].Latitude);
+            Assert.AreEqual(expectedLineString.Coordinates[0].Longitude, actualLineString.Coordinates[0].Longitude);
+            Assert.AreEqual(expectedLineString.Coordinates[0].Altitude, actualLineString.Coordinates[0].Altitude);
+            Assert.AreEqual(expectedLineString.Coordinates[2].Altitude, actualLineString.Coordinates[2].Altitude);
+        }
+
         [Test]
         public void Constructor_No_Coordinates_Throws_Exception()
         {

src/GeoJSON.Text.Test.Unit/Geometry/LineStringTests_Can_Deserialize_With_Altitude.json

@@ -0,0 +1,9 @@
+{
+    "coordinates": [
+        [4.8892593383789062, 52.370725881211314, 10.0],
+        [4.8952674865722656, 52.3711451105601, 10.5],
+        [4.8920917510986328, 52.369310952782627, null],
+        [4.8892593383789062, 52.370725881211314, 10.2]
+    ],
+    "type": "LineString"
+}

src/GeoJSON.Text/Converters/PositionConverter.cs

@@ -2,6 +2,7 @@
 
 using GeoJSON.Text.Geometry;
 using System;
+using System.Collections.Generic;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 
@@ -28,10 +29,9 @@ public override bool CanConvert(Type objectType)
         /// <summary>
         ///     Reads the JSON representation of the object.
         /// </summary>
-        /// <param name="reader">The <see cref="T:Newtonsoft.Json.JsonReader" /> to read from.</param>
-        /// <param name="objectType">Type of the object.</param>
-        /// <param name="existingValue">The existing value of object being read.</param>
-        /// <param name="serializer">The calling serializer.</param>
+        /// <param name="reader">The <see cref="T:System.Text.Json.Utf8JsonReader" /> to read from.</param>
+        /// <param name="type">Type of the object.</param>
+        /// <param name="options">Serializer options.</param>
         /// <returns>
         ///     The object value.
         /// </returns>
@@ -40,17 +40,84 @@ public override IPosition Read(
             Type type,
             JsonSerializerOptions options)
         {
-            double[] coordinates;
-
             try
-            {
-                coordinates = JsonSerializer.Deserialize<double[]>(ref reader, options);
+            { 
+                if (reader.TokenType != JsonTokenType.StartArray)
+                {
+                    throw new ArgumentException("Expected start of array");
+                }
+
+                double lng, lat;
+                double? alt;
+
+                // Read longitude
+                if (!reader.Read())
+                {
+                    throw new ArgumentException("Expected number, but got end of data");
+                }
+                if (reader.TokenType == JsonTokenType.EndArray)
+                {
+                    throw new ArgumentException("Expected 2 or 3 coordinates but got 0");
+                }
+                if (reader.TokenType != JsonTokenType.Number)
+                {
+                    throw new ArgumentException("Expected number but got other type");
+                }
+                lng = reader.GetDouble();
+
+                // Read latitude
+                if (!reader.Read())
+                {
+                    throw new ArgumentException("Expected number, but got end of data");
+                }
+                if (reader.TokenType == JsonTokenType.EndArray)
+                {
+                    throw new ArgumentException("Expected 2 or 3 coordinates but got 1");
+                }
+                if (reader.TokenType != JsonTokenType.Number)
+                {
+                    throw new ArgumentException("Expected number but got other type");
+                }
+                lat = reader.GetDouble();
+
+                // Read altitude, or return if end of array is found
+                if (!reader.Read())
+                {
+                    throw new ArgumentException("Unexpected end of data");
+                }
+                if (reader.TokenType == JsonTokenType.EndArray)
+                {
+                    return new Position(lat, lng);
+                }
+                else if (reader.TokenType == JsonTokenType.Null)
+                {
+                    alt = null;
+                }
+                else if (reader.TokenType == JsonTokenType.Number)
+                {
+                    alt = reader.GetDouble();
+                }
+                else
+                {
+                    throw new ArgumentException("Expected number but got other type");
+                }
+
+                // Check what comes next. Expects end of array.
+                if (!reader.Read())
+                {
+                    throw new ArgumentException("Expected end of array, but got end of data");
+                }
+                if (reader.TokenType != JsonTokenType.EndArray)
+                {
+                    throw new ArgumentException("Expected 2 or 3 coordinates but got >= 4");
+                }
+
+                return new Position(lat, lng, alt);
             }
             catch (Exception e)
             {
                 throw new JsonException("Error parsing coordinates", e);
             }
-            return coordinates?.ToPosition() ?? throw new JsonException("Coordinates cannot be null");
         }
 
         /// <summary>