fix type errors in [DynamicXml] service (#4041)

* fix: type errors in DynamicXml service

* tests: add more tests for DynamicXml

* tests: another DynamicXml service test

services/dynamic/dynamic-xml.service.js

@@ -27,18 +27,11 @@ module.exports = class DynamicXml extends BaseService {
     }
   }
 
-  async handle(namedParams, { url, query: pathExpression, prefix, suffix }) {
+  transform({ pathExpression, buffer }) {
     // e.g. //book[2]/@id
     const pathIsAttr = (
       pathExpression.split('/').slice(-1)[0] || ''
     ).startsWith('@')
-
-    const { buffer } = await this._request({
-      url,
-      options: { headers: { Accept: 'application/xml, text/xml' } },
-      errorMessages,
-    })
-
     const parsed = new DOMParser().parseFromString(buffer)
 
     let values
@@ -47,14 +40,42 @@ module.exports = class DynamicXml extends BaseService {
     } catch (e) {
       throw new InvalidParameter({ prettyMessage: e.message })
     }
-    values = values.map((node, i) =>
-      pathIsAttr ? node.value : node.firstChild.data
-    )
+
+    if (!Array.isArray(values)) {
+      throw new InvalidResponse({
+        prettyMessage: 'unsupported query',
+      })
+    }
+
+    values = values.reduce((accum, node) => {
+      if (pathIsAttr) {
+        accum.push(node.value)
+      } else if (node.firstChild) {
+        accum.push(node.firstChild.data)
+      }
+
+      return accum
+    }, [])
 
     if (!values.length) {
       throw new InvalidResponse({ prettyMessage: 'no result' })
     }
 
-    return renderDynamicBadge({ value: values, prefix, suffix })
+    return { values }
+  }
+
+  async handle(_namedParams, { url, query: pathExpression, prefix, suffix }) {
+    const { buffer } = await this._request({
+      url,
+      options: { headers: { Accept: 'application/xml, text/xml' } },
+      errorMessages,
+    })
+
+    const { values: value } = this.transform({
+      pathExpression,
+      buffer,
+    })
+
+    return renderDynamicBadge({ value, prefix, suffix })
   }
 }