When trying to register a second instance with the same name, then just take the old one. Upgrade prom-client to 6.2.x. Bump 1.2.3

package.json

@@ -1,6 +1,6 @@
 {
   "name": "express-prom-bundle",
-  "version": "1.2.2",
+  "version": "1.2.3",
   "description": "express middleware with popular prometheus metrics in one bundle",
   "main": "src/index.js",
   "keywords": [
@@ -16,7 +16,7 @@
   "license": "MIT",
   "dependencies": {
     "on-finished": "^2.3.0",
-    "prom-client": "^6.1.2",
+    "prom-client": "^6.2.0",
     "url-value-parser": "^1.0.0"
   },
   "devDependencies": {

spec/PromFactorySpec.js

@@ -49,5 +49,17 @@ describe("PromFactory", () => {
         expect(metric.help).toBe("help for test4");
         expect(metric.percentiles).toEqual([0.1, 0.5]);
     });
-
+    it("when regsitered with same name, just return old instance", () => {
+        const metric1 = factory.newSummary(
+            "test4",
+            "help for test4",
+            {percentiles: [0.1, 0.5]}
+        );
+        const metric2 = factory.newSummary(
+            "test4",
+            "help for test4",
+            {percentiles: [0.1, 0.5]}
+        );
+        expect(metric1).toBe(metric2);
+    });
 });

src/PromFactory.js

@@ -15,6 +15,12 @@ module.exports = class {
         const applyParams = Array.prototype.slice.call(args);
         const name = applyParams[0];
         const realName = this.makeRealName(name);
+
+        const existing = this.promClient.register.getSingleMetric(realName);
+        if (existing) {
+            return existing;
+        }
+
         applyParams[0] = realName;
         applyParams.unshift(null); // add some dummy context for apply