Improve error handling when spec isn't valid (#1200)

Check for validation results that will result in an error and reject with that error.

Also, add additional safety around the `conversionResult` handling to avoid generic errors on failure.

Author: Dianoga

packages/docusaurus-plugin-openapi-docs/src/openapi/openapi.ts

@@ -43,9 +43,15 @@ function jsonToCollection(data: OpenApiObject): Promise<Collection> {
       { schemaFaker: false }
     );
     schemaPack.computedOptions.schemaFaker = false;
+
+    // Make sure the schema was properly validated or reject with error
+    if (!schemaPack.validationResult?.result) {
+      return reject(schemaPack.validationResult?.reason);
+    }
+    
     schemaPack.convert((_err: any, conversionResult: any) => {
-      if (!conversionResult.result) {
-        return reject(conversionResult.reason);
+      if (_err || !conversionResult.result) {
+        return reject(_err || conversionResult.reason);
       }
       return resolve(new sdk.Collection(conversionResult.output[0].data));
     });