fix(oas3): attempt to render schemas not resolved by swagger-client (#9629)

Refs #9513

src/core/plugins/oas3/spec-extensions/selectors.js

@@ -47,6 +47,16 @@ export const servers = onlyOAS3(() => (system) => {
   return spec.get("servers", map)
 })
 
+export const findSchema = (state, schemaName) => {
+  const resolvedSchema = state.getIn(
+    ["resolvedSubtrees", "components", "schemas", schemaName],
+    null
+  )
+  const unresolvedSchema = state.getIn(["json", "components", "schemas", schemaName], null)
+
+  return resolvedSchema || unresolvedSchema || null
+}
+
 export const callbacksOperations = onlyOAS3(
   (state, { callbacks, specPath }) =>
     (system) => {

src/core/plugins/oas3/spec-extensions/wrap-selectors.js

@@ -32,6 +32,10 @@ const OAS3NullSelector = onlyOAS3(nullSelector)
  * Wrappers
  */
 
+export const findDefinition = onlyOAS3((state, schemaName) => (system) => {
+  return system.getSystem().specSelectors.findSchema(schemaName)
+})
+
 export const definitions = onlyOAS3(() => (system) => {
   const spec = system.getSystem().specSelectors.specJson()
   const schemas = spec.getIn(["components", "schemas"])