Show path for schema errors

src/oas.gleam

@@ -32,6 +32,13 @@ fn with_default(decoder, value) {
   }
 }
 
+fn add_to_decode_error_path(
+  error: dynamic.DecodeError,
+  path: String,
+) -> dynamic.DecodeError {
+  dynamic.DecodeError(..error, path: list.append(error.path, [path]))
+}
+
 /// This is the root object of the OpenAPI document.
 pub type Document {
   Document(
@@ -176,7 +183,7 @@ fn server_variable_decoder(raw) {
   )(raw)
 }
 
-/// Describes the operations available on a single path. 
+/// Describes the operations available on a single path.
 pub type PathItem {
   PathItem(
     summary: Option(String),
@@ -242,14 +249,11 @@ pub type Components {
   )
 }
 
-fn components_decoder(raw) {
+@internal
+pub fn components_decoder(raw) {
   dynamic.decode4(
     Components,
-    default_field(
-      "schemas",
-      dynamic.dict(dynamic.string, schema_decoder),
-      dict.new(),
-    ),
+    default_field("schemas", schemas_decoder, dict.new()),
     default_field(
       "responses",
       dynamic.dict(dynamic.string, ref_decoder(response_decoder)),
@@ -475,6 +479,29 @@ pub type Schema {
   OneOf(List(Ref(Schema)))
 }
 
+fn schemas_decoder(raw) {
+  dynamic.dict(dynamic.string, dynamic.dynamic)(raw)
+  |> result.then(fn(dict_with_dyn) {
+    dict.fold(
+      over: dict_with_dyn,
+      from: Ok(dict.new()),
+      with: fn(acc, key, value) {
+        case acc {
+          Error(errors) -> Error(errors)
+          Ok(dict) -> {
+            case schema_decoder(value) {
+              Ok(schema) -> Ok(dict.insert(dict, key, schema))
+              Error(errors) -> {
+                Error(list.map(errors, add_to_decode_error_path(_, key)))
+              }
+            }
+          }
+        }
+      },
+    )
+  })
+}
+
 fn schema_decoder(raw) {
   dynamic.any([
     dynamic.field("type", fn(field) {

test/oas_test.gleam

@@ -1,4 +1,5 @@
 import gleam/dict
+import gleam/dynamic
 import gleam/json
 import gleam/result
 import gleeunit
@@ -13,6 +14,10 @@ fn parse(data) {
   json.decode(data, oas.decoder)
 }
 
+fn decode_components(data) {
+  json.decode(data, oas.components_decoder)
+}
+
 pub fn minimal_doc_test() {
   let doc =
     "{\"openapi\": \"3.0.0\", \"info\": {\"title\": \"Test\", \"version\": \"0.x.x\" }}"
@@ -30,7 +35,7 @@ pub fn minimal_doc_test() {
 pub fn minimal_doc_null_fields_test() {
   let doc =
     "{
-      \"openapi\": \"3.0.0\", 
+      \"openapi\": \"3.0.0\",
       \"info\": {\"title\": \"Test\", \"version\": \"0.x.x\" },
       \"jsonSchemaDialect\": null,
       \"servers\": null,
@@ -83,3 +88,50 @@ pub fn empty_paths_test() {
   dict.get(paths, "/")
   |> should.be_ok
 }
+
+pub fn valid_object_schema_test() {
+  let data =
+    "{
+      \"schemas\": {
+        \"thing\": {
+          \"type\": \"object\",
+          \"properties\": {
+            \"title\": {
+              \"type\": \"string\"
+            }
+          }
+        }
+      }
+    }"
+
+  data
+  |> decode_components
+  |> should.be_ok
+}
+
+pub fn invalid_object_schema_test() {
+  let data =
+    "{
+      \"schemas\": {
+        \"thing\": {
+          \"properties\": {
+            \"title\": {
+              \"type\": \"string\"
+            }
+          }
+        }
+      }
+    }"
+
+  data
+  |> decode_components
+  |> should.equal(
+    Error(
+      json.UnexpectedFormat([
+        dynamic.DecodeError(expected: "another type", found: "Object", path: [
+          "schemas", "thing",
+        ]),
+      ]),
+    ),
+  )
+}