Merge #182

182: feature without 'properties' key doesn't error r=urschrei a=michaelkirk

- [x] I agree to follow the project's [code of conduct](https://github.com/georust/geo/blob/master/CODE_OF_CONDUCT.md).
- [x] I added an entry to `CHANGES.md` if knowledge of this change could be valuable to users.
---

I think "properties" is actually a required field for Feature and FeatureCollections, but sometimes in the wild it's missing. 

In the interest of being strict about what we emit while being permissive about what we accept, I think it'd be helpful for users to go forward when there is no properties key, and treat it just like null or empty properties.

FWIW, ogr2ogr handles this without exploding.



Co-authored-by: Michael Kirk <[email protected]>

CHANGES.md

@@ -1,5 +1,10 @@
 # Changes
 
+## UNRELEASED
+
+* Allow parsing Feature/FeatureCollection that are missing a "properties" key.
+  * <https://github.com/georust/geojson/pull/182>
+
 ## 0.22.3
 
 * Added `FromIterator<Feature>` impl for `FeatureCollection`

src/geojson.rs

@@ -451,6 +451,31 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_missing_properties_key() {
+        let json_value = json!({
+            "type": "Feature",
+            "geometry": {
+                "type": "Point",
+                "coordinates": [102.0, 0.5]
+            },
+        });
+
+        assert!(json_value.is_object());
+
+        let geojson: GeoJson = json_value.try_into().unwrap();
+        assert_eq!(
+            geojson,
+            GeoJson::Feature(Feature {
+                bbox: None,
+                geometry: Some(Geometry::new(Value::Point(vec![102.0, 0.5]))),
+                id: None,
+                properties: None,
+                foreign_members: None,
+            })
+        );
+    }
+
     #[test]
     fn test_invalid_json() {
         let geojson_str = r#"{

src/lib.rs

@@ -389,6 +389,10 @@ pub struct Feature {
     /// Properties
     ///
     /// [GeoJSON Format Specification § 3.2](https://tools.ietf.org/html/rfc7946#section-3.2)
+    ///
+    /// NOTE: This crate will permissively parse a Feature whose json is missing a `properties` key.
+    /// Because the spec implies that the `properties` key must be present, we will always include
+    /// the `properties` key when serializing.
     pub properties: Option<json::JsonObject>,
     /// Foreign Members
     ///

src/util.rs

@@ -103,11 +103,12 @@ pub fn get_foreign_members(object: JsonObject) -> Result<Option<JsonObject>, Err
 
 /// Used by Feature
 pub fn get_properties(object: &mut JsonObject) -> Result<Option<JsonObject>, Error> {
-    let properties = expect_property(object, "properties")?;
+    let properties = expect_property(object, "properties");
     match properties {
-        JsonValue::Object(x) => Ok(Some(x)),
-        JsonValue::Null => Ok(None),
-        _ => Err(Error::PropertiesExpectedObjectOrNull(properties)),
+        Ok(JsonValue::Object(x)) => Ok(Some(x)),
+        Ok(JsonValue::Null) | Err(Error::ExpectedProperty(_)) => Ok(None),
+        Ok(not_a_dictionary) => Err(Error::PropertiesExpectedObjectOrNull(not_a_dictionary)),
+        Err(e) => Err(e)
     }
 }