error message for bad configuration is ambiguous

[shoenig]

If there is any problem with the specified config file, the generic help message is displayed with no information about what was wrong. We should have detailed error messages so it's not a guessing game.

[xavierhardy]

Yes, this is clearly needed, just saying 400 is not sufficient.

[tavisto]

A simple way to do this would to be to simply pass the marathon output from the body of the response to the error message like so:

diff --git a/app.go b/app.go
index d0da79f..ba31699 100644
--- a/app.go
+++ b/app.go
@@ -237,7 +237,7 @@ func (a AppUpdate) update(id string, body io.ReadCloser) {
 	Check(e == nil, "failed to get response", e)
 	defer response.Body.Close()
 	sc := response.StatusCode
-	Check(sc == 200, "bad status code", sc)
+	Check(sc == 200, "bad status code", sc, a.format.Format(response.Body, a.Humanize))
 	fmt.Println(a.format.Format(response.Body, a.Humanize))
 }

This produces a message like so (I have a bad boolean in the json):

bad status code 400 {"message":"Invalid JSON","details":[{"path":"/container/docker/forcePullImage","errors":["error.expected.jsboolean"]}]}

Or wrap it all up in a nice format function etc. Just saying 400 is very frustrating especially when marathon already told you what was wrong.

If you like this idea I will be more than happy to write a patch and submit a PR.

[xavierhardy]

Yes, that should be sufficient.

[shoenig]

@tavisto if you have a PR ready, I will gladly merge it

[tavisto]

PR here: https://github.com/shoenig/marathonctl/pull/39