split includeCustomLabels into customLabels and transformLabels

spec/index.spec.js

@@ -258,10 +258,10 @@ describe('index', () => {
       });
   });
 
-  it('includeCustomLabels={foo: "bar"} adds foo="bar" label to metrics', done => {
+  it('customLabels={foo: "bar"} adds foo="bar" label to metrics', done => {
     const app = express();
     const instance = bundle({
-      includeCustomLabels: {foo: "bar"}
+      customLabels: {foo: 'bar'}
     });
     app.use(instance);
     app.use('/test', (req, res) => res.send('it worked'));
@@ -279,6 +279,33 @@ describe('index', () => {
       });
   });
 
+  it('tarnsformLabels can set label values', done => {
+    const app = express();
+    const instance = bundle({
+      includePath: true,
+      customLabels: {foo: 'bar'},
+      transformLabels: labels => {
+        labels.foo = 'baz';
+        labels.path += '/ok';
+      }
+    });
+    app.use(instance);
+    app.use('/test', (req, res) => res.send('it worked'));
+    const agent = supertest(app);
+    agent
+      .get('/test')
+      .end(() => {
+        agent
+          .get('/metrics')
+          .end((err, res) => {
+            expect(res.status).toBe(200);
+            expect(res.text).toMatch(/foo="baz"/);
+            expect(res.text).toMatch(/path="\/test\/ok"/);
+            done();
+          });
+      });
+  });
+
   it('Koa: metrics returns up=1', done => {
     const app = new Koa();
     const bundled = bundle({

src/index.js

@@ -38,30 +38,6 @@ function prepareMetricNames(opts, metricTemplates) {
   return names;
 }
 
-function hasCustomLabels(opts, strict){
-  strict = strict || false;
-  if (opts.hasOwnProperty('includeCustomLabels')){
-    let dtype;
-    try {
-      dtype = opts.includeCustomLabels.constructor.name;
-    } catch (e) {
-      dtype = opts.includeCustomLabels;
-    }
-    if (dtype === 'Object') {
-      return true;
-    }
-    if (strict) {
-      throw new Error(
-        'express-prom-bundle detected invalid data type for option: includeCustomLabels.\n'
-        + 'Expected: Object\n'
-        + 'Passed: ' + dtype
-      );
-    }
-  }
-
-  return false;
-}
-
 function main(opts) {
   opts = Object.assign(
     {
@@ -105,8 +81,8 @@ function main(opts) {
       if (opts.includePath) {
         labels.push('path');
       }
-      if (hasCustomLabels(opts, true)){
-        labels.push.apply(labels, Object.keys(opts.includeCustomLabels));
+      if (opts.customLabels){
+        labels.push.apply(labels, Object.keys(opts.customLabels));
       }
       const metric = new promClient.Histogram({
         name: httpMtricName,
@@ -159,11 +135,11 @@ function main(opts) {
         if (opts.includePath) {
           labels.path = opts.normalizePath(req, opts);
         }
-        if (hasCustomLabels(opts, true)) {
-          let customLabels = opts.includeCustomLabels;
-          for (let key in customLabels){
-            labels[key] = customLabels[key];
-          }
+        if (opts.customLabels) {
+          Object.assign(labels, opts.customLabels);
+        }
+        if (opts.transformLabels) {
+          opts.transformLabels(labels, req, res);
         }
         timer();
       });