2000701 - The Glean Error Reporting Mechanism doesn't count "ping submitted with invalid reason" as an error

Status: NEW

(Data Platform and Tools :: Glean: SDK, enhancement, P4)

Description

[Chris H-C :chutten]

If you submit a ping with a value for reason that isn't defined in its definition, the ping is submitted with an empty reason and a warning is logged at ERROR level. And that's it.

This doesn't match the usual Glean Error Reporting Mechanism structure we expect for metrics. In my mind, submitting an undefined reason ought to:

1. Record an invalid_value error, with the name of the ping as the label, to be submitted in the (next) offending ping as well as the "health" ping
2. Communicate any stored errors via testBeforeNextSubmit/testSubmission similar to test_get_num_recorded_errors/test_get_value (See also bug 1978438)

Point 2 might be too annoying to get quickly done, so I'd accept splitting that off if it proves difficult in the hopes of getting Point 1 landed more quickly so we can have monitoring and documentation.