Simpler syntax for fillDescriptions items with limited choices

[kpedro88]

I recently learned (in review of #30850) that fillDescriptions can restrict the allowed choices for a configuration parameter using ifValue(). However, the syntax for this is currently a bit clunky:

  desc.ifValue(edm::ParameterDescription<std::string>("mode", "PseudoAsync", true),
      "Sync" >> edm::EmptyGroupDescription() or
      "Async" >> edm::EmptyGroupDescription() or
      "PseudoAsync" >> edm::EmptyGroupDescription());

This syntax is intended to allow for switching between more complex parameter groups. However, in the case of a simple choice (such as above), it would be nice to have a simpler syntax. For example, the allowed choices could just be provided as a vector.

[kpedro88]

assign core

[cmsbuild]

New categories assigned: core

@Dr15Jones,@smuzaffar,@makortel you have been requested to review this Pull request/Issue and eventually sign? Thanks

[cmsbuild]

A new Issue was created by @kpedro88 Kevin Pedro.

@Dr15Jones, @dpiparo, @silviodonato, @smuzaffar, @makortel, @qliphy can you please review it and eventually sign/assign? Thanks.

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[makortel]

Here is an earlier discussion on the topic https://hypernews.cern.ch/HyperNews/CMS/get/progQuestions/331.html

[Dr15Jones]

How about

desc.ifValue(edm::ParameterDescription<std::string>("mode", "PseudoAsync", true),
             edm::allowedValues("Sync", "Async", "PseudoAsync"));

?

In a quick test I was able to make that work. All it needed was the new templated function edm::allowedValues which does exactly what your earlier code did but behind the scenes.

[kpedro88]

That looks good to me.

[makortel]

@Dr15Jones How necessary the desc.ifValue() is? (for a quick solution it probably is)

I'm just wondering if we should think about a more general mechanism to specify constraints on allowed values.

[Dr15Jones]

See #30950

[makortel]

+1

Done in #30950

[cmsbuild]

This issue is fully signed and ready to be closed.