prometheus: fix extends from query, ensuring array fields

constants.js

@@ -7,4 +7,6 @@ module.exports = {
   },
 
   ignoreAssetPattern: /(^data:)/,
+
+  arrayParams: ['labels', 'internalPatterns', 'mimeTypes', 'mimeTypePatterns', 'ignorePatterns'],
 };

prometheus/index.js

@@ -5,8 +5,9 @@ const promClient = require('prom-client');
 const { get } = require('lodash');
 const Store = require('./store');
 const Settings = require('./settings');
+const constants = require('../constants');
 const getMetrics = require('..');
-const { env, parseLabelsParam } = require('./utils');
+const { env, parseLabelsParam, ensureArrayParam } = require('./utils');
 
 const store = new Store({
   cacheTTL: Settings.onDemandQueryCacheTTL,
@@ -253,6 +254,8 @@ app.get(Settings.path, async (req, res, next) => {
 
       if (!cached && store.busy) throw new Error('Ops.. Busy service!');
 
+      constants.arrayParams.forEach((p) => ensureArrayParam(req.query, p));
+
       const config = { ...Settings.defaults, ...req.query };
       config.url = req.query.url;
       config.labels = parseLabelsParam(req.query.labels || []);

prometheus/utils.js

@@ -25,10 +25,20 @@ function parseLabelsParam(arr) {
     : {};
 }
 
+function ensureArrayParam(query, key) {
+  if (key in query) {
+    if (!isArray(query[key])) {
+      // eslint-disable-next-line no-param-reassign
+      query[key] = [query[key]];
+    }
+  }
+}
+
 module.exports = {
   env,
   envArray,
   envBool,
   envInt,
   parseLabelsParam,
+  ensureArrayParam,
 };