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Override derived label value case - #136
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This applies to individual entries in the derived implementation Signed-off-by: Eric Hodel <drbrain@segment7.net>
When deriving label values for an enum the default case of the label matches the identifier case. This forced derived label values to use rust's case rules which may not match up with metrics exported from other programs, or metrics from other crates that export prometheus metrics. This change adds the ability to set the case of a derived value label to all-lowercase or all-uppercase for the entire struct in addition to for an individual label from the prior commit. Signed-off-by: Eric Hodel <drbrain@segment7.net>
Signed-off-by: Eric Hodel <drbrain@segment7.net>
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| /// For variants you can use `#[prometheus(lower)]` or `#[prometheus(upper)]` to set the case for | ||
| /// only that variant. |
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Do you have a concrete use-case where one would upper or lower case a specific variant only?
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I do not
it might be better to remove this and wait for a motivated individual to plumb serde in to label generation which could provide all manner of derive customization
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Do you want me to remove per-variant case changing?
| let body = match ast.clone().data { | ||
| syn::Data::Struct(_) => { | ||
| panic!("Can not derive EncodeLabel for struct.") | ||
| panic!("Can not derive EncodeLabelValue for struct.") |
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| "lower" => config.value_case = ValueCase::Lower, | ||
| "upper" => config.value_case = ValueCase::Upper, | ||
| invalid => { | ||
| return Err(syn::Error::new( | ||
| case.span(), | ||
| format!( | ||
| "value case may only be \"lower\" or \"upper\", not \"{invalid}\"" | ||
| ), | ||
| )) |
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To de-duplicate this code with the one above in line 146, how about implementing FromStr for ValueCase?
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It will take me some time, but I think I can do this
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By default deriving label values for an enum:
Results in a label that matches the variant identifier's, here
"One".To allow compatibility with metrics emitted from other processes, or compatibility when switching crates, this PR allows overriding the default case for EncodeLabelValue for an entire enum or for individual enum entries.
Would have labels for values
EnumLabel::OneandEnumLabel::Twowould be"one"and"two"respectively.The case can be overridden for a single variant as well:
Would have labels for values
EnumLabel::OneandEnumLabel::Twowould be"one"and"Two"respectively.