Convert string coordinates to floats, or raise an error

lib/geo/json/decoder.ex

@@ -46,7 +46,7 @@ defmodule Geo.JSON.Decoder do
           Enum.map(Map.get(geo_json, "geometries"), fn x ->
             do_decode(
               Map.get(x, "type"),
-              Map.get(x, "coordinates"),
+              ensure_numeric(x["coordinates"]),
               Map.get(x, "properties", %{}),
               crs
             )
@@ -62,7 +62,7 @@ defmodule Geo.JSON.Decoder do
 
         do_decode(
           Map.get(geo_json, "type"),
-          Map.get(geo_json, "coordinates"),
+          ensure_numeric(geo_json["coordinates"]),
           Map.get(geo_json, "properties", %{}),
           crs
         )
@@ -205,7 +205,12 @@ defmodule Geo.JSON.Decoder do
         properties: properties
       }
     else
-      do_decode(Map.get(geometry, "type"), Map.get(geometry, "coordinates"), properties, nil)
+      do_decode(
+        Map.get(geometry, "type"),
+        ensure_numeric(geometry["coordinates"]),
+        properties,
+        nil
+      )
     end
   end
 
@@ -231,4 +236,47 @@ defmodule Geo.JSON.Decoder do
   defp get_srid(nil) do
     nil
   end
+
+  # Fast paths for the common (correct) cases
+  defp ensure_numeric(num) when is_number(num), do: num
+  defp ensure_numeric([x, y] = l) when is_number(x) and is_number(y), do: l
+
+  defp ensure_numeric([x, y, z] = l)
+       when is_number(x) and is_number(y) and (is_number(z) or is_nil(z)) do
+    l
+  end
+
+  defp ensure_numeric([x, y, z, m] = l)
+       when is_number(x) and is_number(y) and (is_number(z) or is_nil(z)) and
+              (is_number(m) or is_nil(z)) do
+    l
+  end
+
+  defp ensure_numeric(l) when is_list(l) do
+    Enum.map(l, fn
+      num when is_number(num) ->
+        num
+
+      str when is_binary(str) ->
+        try do
+          String.to_float(str)
+        catch
+          ArgumentError ->
+            raise ArgumentError, "expected a numeric coordinate, got the string #{inspect(str)}"
+        end
+
+      nil ->
+        nil
+
+      l when is_list(l) ->
+        Enum.map(l, &ensure_numeric/1)
+
+      other ->
+        raise ArgumentError, "expected a numeric coordinate, got: #{inspect(other)}"
+    end)
+  end
+
+  defp ensure_numeric(other) do
+    raise ArgumentError, "expected a numeric coordinate, got: #{inspect(other)}"
+  end
 end

test/geo/json_test.exs

@@ -387,6 +387,67 @@ defmodule Geo.JSON.Test do
     assert geom.geometries == []
   end
 
+  test "Decode seamlessly converts coordinates that are numbers-as-strings" do
+    check all(
+            x <- float(),
+            y <- float()
+          ) do
+      json = """
+        {
+          "properties": {},
+          "geometry": {
+            "type": "Point",
+            "coordinates": ["#{x}", "#{y}"]
+          },
+          "type": "Feature"
+        }
+      """
+
+      assert %Geo.Point{coordinates: {^x, ^y}} = Jason.decode!(json) |> Geo.JSON.decode!()
+    end
+  end
+
+  test "Decode rejects geometries with non-numeric coordinates" do
+    for {bad_x, bad_y} <- [
+          {" 100.0", "0.0"},
+          {"100.0", "0.0?"},
+          {"100.", "0.0"},
+          {"100.0", nil, "0.0"}
+        ] do
+      json = """
+        {
+          "properties": {},
+          "geometry": {
+            "type": "Point",
+            "coordinates": [#{inspect(bad_x)}, #{inspect(bad_y)}]
+          },
+          "type": "Feature"
+        }
+      """
+
+      assert_raise ArgumentError, fn ->
+        Jason.decode!(json) |> Geo.JSON.decode!()
+      end
+    end
+  end
+
+  test "Decode rejects geometries with garbage coordinates" do
+    json = """
+      {
+        "properties": {},
+        "geometry": {
+          "type": "Point",
+          "coordinates": {"x": 1.0, "y": 2.0}
+        },
+        "type": "Feature"
+      }
+    """
+
+    assert_raise ArgumentError, fn ->
+      Jason.decode!(json) |> Geo.JSON.decode!()
+    end
+  end
+
   property "encodes and decodes back to the correct Point struct" do
     check all(
             x <- float(),
@@ -522,7 +583,7 @@ defmodule Geo.JSON.Test do
 
     geom = Jason.decode!(json) |> Geo.JSON.decode!()
 
-    assert %GeometryCollection{} = geom
+    assert %Geo.GeometryCollection{} = geom
     assert length(geom.geometries) == 2
     assert Enum.all?(geom.geometries, &match?(%Geo.MultiPolygon{}, &1))
     assert geom.properties["id"] == "FLC017"