chore: response to review comments

pywr-schema/src/parameters/doc_examples/threshold_returned_values1.json

@@ -0,0 +1,25 @@
+{
+  "type": "Threshold",
+  "meta": {
+      "name": "my-threshold-param"
+  },
+  "metric": {
+      "type": "Node",
+      "name": "river-1"
+  },
+  "threshold": {
+      "type": "Constant",
+      "value": 5.0
+  },
+  "predicate": "LT",
+  "returned_metrics": [
+    {
+      "type": "Constant",
+      "value": 1.5
+    },
+    {
+      "type": "Constant",
+      "value": 0.5
+    }
+  ]
+}

pywr-schema/src/parameters/mod.rs

@@ -191,18 +191,7 @@ impl Parameter {
             Self::Min(p) => pywr_core::parameters::ParameterType::Parameter(p.add_to_model(network, args)?),
             Self::Negative(p) => pywr_core::parameters::ParameterType::Parameter(p.add_to_model(network, args)?),
             Self::Polynomial1D(p) => pywr_core::parameters::ParameterType::Parameter(p.add_to_model(network, args)?),
-            Self::Threshold(p) => match p.add_to_model(network, args)? {
-                pywr_core::parameters::ParameterType::Index(i) => pywr_core::parameters::ParameterType::Index(i),
-                pywr_core::parameters::ParameterType::Parameter(p) => {
-                    pywr_core::parameters::ParameterType::Parameter(p)
-                }
-                pywr_core::parameters::ParameterType::Multi(_) => {
-                    return Err(SchemaError::LoadParameter {
-                        name: p.meta.name.to_string(),
-                        error: String::from("Threshold parameter cannot be a multi-parameter."),
-                    })
-                }
-            },
+            Self::Threshold(p) => p.add_to_model(network, args)?,
             Self::TablesArray(p) => pywr_core::parameters::ParameterType::Parameter(p.add_to_model(network, args)?),
             Self::Python(p) => p.add_to_model(network, args)?,
             Self::Delay(p) => pywr_core::parameters::ParameterType::Parameter(p.add_to_model(network, args)?),
@@ -722,8 +711,21 @@ mod tests {
             let p = entry.unwrap().path();
             if p.is_file() {
                 let data = fs::read_to_string(&p).unwrap_or_else(|_| panic!("Failed to read file: {:?}", p));
-                let _: Parameter =
+
+                let value: serde_json::Value =
                     serde_json::from_str(&data).unwrap_or_else(|_| panic!("Failed to deserialize: {:?}", p));
+
+                match value {
+                    serde_json::Value::Object(o) => {
+                        let _ = serde_json::from_value::<Parameter>(serde_json::Value::Object(o))
+                            .unwrap_or_else(|_| panic!("Failed to deserialize: {:?}", p));
+                    }
+                    serde_json::Value::Array(_) => {
+                        let _ = serde_json::from_value::<Vec<Parameter>>(value)
+                            .unwrap_or_else(|_| panic!("Failed to deserialize: {:?}", p));
+                    }
+                    _ => panic!("Expected JSON object: {:?}", p),
+                }
             }
         }
     }

pywr-schema/src/parameters/thresholds.rs

@@ -58,19 +58,28 @@ impl From<Predicate> for pywr_core::parameters::Predicate {
 /// A parameter that compares a metric against a threshold metric
 ///
 /// The metrics are compared using the given predicate and the result is returned as an index. If the comparison
-/// evaluates to true the index is 1, otherwise it is 0.
+/// evaluates to true the index is 1, otherwise it is 0. When values are provided for the `returned_metrics` attribute,
+/// these values are returned instead of the index. If the predicate comparison evaluates to false the first value is
+/// returned, if it is true the second value is returned.
 ///
 /// The parameter has different representations in core depending on the `returned_metrics` attribute. If values are
-/// given then two parameters are added to the model. The first a [`pywr_core::parameters::ThresholdParameter`], which
-/// is set as the index parameter of a [`pywr_core::parameters::IndexedArrayParameter`] containing the `returned_metrics`
+/// set for `returned_metrics` then two parameters are added to the model. The first a
+/// [`pywr_core::parameters::ThresholdParameter`], which is set as the index parameter of a
+/// [`pywr_core::parameters::IndexedArrayParameter`] containing the `returned_metrics`
 /// values.
 ///
-/// An equivalent representation could be achieved by defining the two parameters in the schema directly:
+/// # Examples
+///
 /// ```JSON
-#[doc = include_str!("doc_examples/threshold_returned_values.json")]
+#[doc = include_str!("doc_examples/threshold_returned_values1.json")]
 /// ```
+/// Note that the name specified in the model JSON for the parameter in this example is assigned to the core
+/// `IndexedArrayParameter`. The core `ThresholdParameter` is given an additional sub-name of `threshold`.
 ///
-///
+/// An equivalent representation could be achieved by defining the two parameters separately in the model JSON:
+/// ```JSON
+#[doc = include_str!("doc_examples/threshold_returned_values2.json")]
+/// ```
 #[derive(serde::Deserialize, serde::Serialize, Debug, Clone, JsonSchema, PywrVisitAll)]
 #[serde(deny_unknown_fields)]
 pub struct ThresholdParameter {