Investigate using errcheck

[tomwilkie]

https://github.com/kisielk/errcheck

[peterbourgon]

Sure, we can run it occasionally.

[tomwilkie]

It seems to highlight a few times when we don't check the err:

vagrant@ubuntu-14:~/src/github.com/weaveworks/scope$ errcheck github.com/weaveworks/scope/app
github.com/weaveworks/scope/app/api_topology.go:62:14   r.ParseForm()
github.com/weaveworks/scope/app/api_topology.go:122:18  defer conn.Close()
github.com/weaveworks/scope/app/api_topology.go:143:24  conn.SetWriteDeadline(time.Now().Add(websocketTimeout))
github.com/weaveworks/scope/app/api_topology_test.go:134:16 defer ws.Close()
github.com/weaveworks/scope/app/main.go:46:16   defer w.Close()
github.com/weaveworks/scope/app/main.go:56:16   defer f.Close()
github.com/weaveworks/scope/app/main.go:66:18   defer os.Remove(*pidfile)
github.com/weaveworks/scope/app/scope_test.go:63:16 res.Body.Close()
github.com/weaveworks/scope/app/server_helpers.go:12:27 json.NewEncoder(w).Encode(response)
vagrant@ubuntu-14:~/src/github.com/weaveworks/scope$ errcheck github.com/weaveworks/scope/probe
github.com/weaveworks/scope/probe/main.go:56:25 go http.ListenAndServe(*httpListen, nil)
github.com/weaveworks/scope/probe/process_mapper.go:74:10   fh.Close()
github.com/weaveworks/scope/probe/process_mapper.go:113:10  f.Close()
github.com/weaveworks/scope/probe/process_mapper_test.go:20:20  defer os.RemoveAll(tmp)
github.com/weaveworks/scope/probe/process_mapper_test.go:47:16  os.RemoveAll(tmp)
github.com/weaveworks/scope/probe/process_mapper_test.go:52:16  os.RemoveAll(tmp)

[tomwilkie]

You can filter out close, which it seems pretty safe to ignore:

vagrant@ubuntu-14:~/src/github.com/weaveworks/scope$ errcheck -ignore 'Close' github.com/weaveworks/scope/app
github.com/weaveworks/scope/app/api_topology.go:62:14   r.ParseForm()
github.com/weaveworks/scope/app/api_topology.go:143:24  conn.SetWriteDeadline(time.Now().Add(websocketTimeout))
github.com/weaveworks/scope/app/main.go:66:18   defer os.Remove(*pidfile)
github.com/weaveworks/scope/app/server_helpers.go:12:27 json.NewEncoder(w).Encode(response)

[peterbourgon]

All of those are effectively harmless. But, I'm happy to throw in some checks. (And remove that pidfile stuff altogether.)