Improve error message (rfc7807)

[gcatanese]

@antihax (2017/11) @grokify (2018/07) @kemokemo (2018/09) @jirikuncar (2021/01) @ph4r5h4d (2021/04)

Improve error message when error returns RFC7807 model
Fix #13679

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[wing328]

looks like this code block uses 4-space instead of tabs for indention, can you update it to use tabs instead?

[wing328]

please use tabs instead of 4-space

[gcatanese]

@wing328 It should be ok now, I had to remove the Mustache plugin for IntelliJ that was altering my indentation (sorry to waste your time)

[jmontroy90]

@gcatanese This PR introduced a panic into our code because it was trying to parse our custom error response according to RFC7807. Our custom error response doesn't have a Title or Detail field, so both of those reflect-based lookups are invalid and the first one hit in the code path (Title) caused a panic. Can you take a look?

Specifically, can the code check to ensure that the given error response conforms to RFC7807 before it tries to extract out its fields?

[gcatanese]

Hey @jmontroy90 I had a look and I cannot reproduce the problem. The formatErrorMessage checks if the field exists before extracting it

	metaValue := reflect.ValueOf(v).Elem()

	field := metaValue.FieldByName("Title")
	if field != (reflect.Value{}) {
		str = fmt.Sprintf("%s", field.Interface())
	}

Am I missing something?

[jmontroy90]

@gcatanese fair enough - I'll do some homework to reproduce and get back to you.

[thiagoarrais]

@jmontroy90: is your problem maybe related to #15147?