Fix unbound ctx.onerror on streamed response Counter (PROD-84255)

index.js

@@ -67,7 +67,7 @@ function buildRiviere(options = {}) {
         let counter;
 
         if (!length && ctx.body && ctx.body.readable) {
-          ctx.body = ctx.body.pipe((counter = Counter())).on('error', ctx.onerror);
+          ctx.body = ctx.body.pipe((counter = Counter())).on('error', err => ctx.onerror(err));
         }
 
         const res = ctx.res;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@workablehr/riviere",
-  "version": "1.22.0",
+  "version": "1.22.1",
   "description": "log inbound/outbound HTTP traffic",
   "types": "./types/riviere.d.ts",
   "main": "index.js",

test/indexTest.js

@@ -116,7 +116,8 @@ describe('riviere', () => {
       response: {},
       body: readable,
       res: writable,
-      onerror: () => {}
+      // Non-arrow so a binding regression would surface as wrong `this`
+      onerror: function() {}
     };
 
     const next = () => {};
@@ -133,4 +134,42 @@ describe('riviere', () => {
     await end;
     ctx.state.calculatedContentLength.should.equal(26);
   });
+
+  it('should call ctx.onerror bound to ctx when streamed body errors', async function() {
+    const readable = new Readable({ read() {} });
+    const writable = new Writable({ write() {} });
+
+    const middleware = riviere({
+      logger: {
+        info: sandbox.spy()
+      }
+    });
+
+    const streamError = new Error('client disconnect');
+    const onerror = sandbox.spy(function(err) {
+      // Mimic Koa's Context#onerror which uses `this.app.emit(...)`
+      this.app.emit('error', err, this);
+    });
+
+    const ctx = {
+      state: {},
+      response: {},
+      body: readable,
+      res: writable,
+      app: {
+        emit: sandbox.spy()
+      },
+      onerror
+    };
+
+    await middleware(ctx, () => {});
+
+    ctx.body.emit('error', streamError);
+
+    onerror.calledOnce.should.equal(true);
+    onerror.calledWith(streamError).should.equal(true);
+    onerror.thisValues[0].should.equal(ctx);
+    ctx.app.emit.calledOnce.should.equal(true);
+    ctx.app.emit.calledWith('error', streamError, ctx).should.equal(true);
+  });
 });