Support generic default values

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## [0.8.9] - **in-dev**
+### Changed:
+- Support generic default values in `default` attributes (https://github.com/GREsau/schemars/pull/83)
+
 ## [0.8.8] - 2021-11-25
 ### Added:
 - Implement `JsonSchema` for types from `rust_decimal` and `bigdecimal` crates (https://github.com/GREsau/schemars/pull/101)

schemars/tests/default.rs

@@ -54,3 +54,14 @@ pub struct NotSerialize;
 fn schema_default_values() -> TestResult {
  test_default_generated_schema::<MyStruct>("default")
 }
+
+#[derive(JsonSchema, Debug)]
+pub struct StructWithGenericDefaults {
+ #[serde(default = "Vec::new")]
+ pub a_vec: Vec<String>,
+}
+
+#[test]
+fn schema_with_generic_default_value() -> TestResult {
+ test_default_generated_schema::<StructWithGenericDefaults>("generic_default")
+}

schemars/tests/expected/generic_default.json

@@ -0,0 +1,14 @@
+{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "title": "StructWithGenericDefaults",
+ "type": "object",
+ "properties": {
+ "a_vec": {
+ "default": [],
+ "type": "array",
+ "items": {
+ "type": "string"
+ }
+ }
+ }
+}

schemars_derive/src/schema_exprs.rs

@@ -581,7 +581,7 @@ fn field_default_expr(field: &Field, container_has_default: bool) -> Option<Toke
  quote!(container_default.#member)
  }
  SerdeDefault::Default => quote!(<#ty>::default()),
- SerdeDefault::Path(path) => quote!(#path()),
+ SerdeDefault::Path(path) => quote!({ #path() as #ty }),
  };
 
  let default_expr = match field.serde_attrs.skip_serializing_if() {