FlowscopeDocs

T305

null arm on a value that cannot be null

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Severity Warning

A match has a null arm, but the subject’s type is not nullable, so the arm can never run. This often happens after a value was already defaulted with ??.

Remove the null arm, or match on the original nullable value instead.

Failing example

Flowscope Script
script "OI direction"
data oi = subscribe(data.oi)
on oi.close {
  let change = (oi.close ?? 0.0) - (oi.close[1] ?? 0.0)
  let word = match change {
    null => "unknown"
    v if v > 0.0 => "rising"
    _ => "falling"
  }
  log.debug(word)
}

Fixed example

Flowscope Script
script "OI direction"
data oi = subscribe(data.oi)
on oi.close {
  let change = oi.close - oi.close[1]
  let word = match change {
    null => "unknown"
    v if v > 0.0 => "rising"
    _ => "falling"
  }
  log.debug(word)
}