Update how type information is passed from Phlex to FORM

[pcanal]

Given that ROOT knows about the type via their std::type_info (and their C++ names) and that we can not lookup a std::type_info from an std::type_index (but the reverse is supported by the C++ standard), we need to pass around the type_info (otherwise we need to build a map of supported types).

This solves #199

[codecov]

Codecov Report

❌ Patch coverage is 50.98039% with 25 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
form/root_storage/root_tbranch_container.cpp	25.00%	18 Missing and 3 partials ⚠️
form/storage/storage.cpp	57.14%	2 Missing and 1 partial ⚠️
form/storage/storage_container.cpp	0.00%	1 Missing ⚠️

❌ Your patch status has failed because the patch coverage (50.98%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.
❌ Your project status has failed because the head coverage (75.21%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

@@            Coverage Diff             @@
##             main     #252      +/-   ##
==========================================
- Coverage   76.66%   75.21%   -1.45%     
==========================================
  Files         124      124              
  Lines        2725     2905     +180     
  Branches      475      510      +35     
==========================================
+ Hits         2089     2185      +96     
- Misses        442      501      +59     
- Partials      194      219      +25     

Flag	Coverage Δ
unittests	75.21% <50.98%> (-1.45%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
form/form/form.cpp	74.19% <100.00%> (-2.95%)	⬇️
form/form/form.hpp	100.00% <ø> (ø)
form/form_module.cpp	84.78% <100.00%> (-2.72%)	⬇️
form/persistence/ipersistence.hpp	100.00% <ø> (ø)
form/persistence/persistence.cpp	84.31% <100.00%> (ø)
form/persistence/persistence.hpp	100.00% <ø> (ø)
form/root_storage/root_tbranch_container.hpp	100.00% <ø> (ø)
form/root_storage/root_ttree_container.cpp	46.15% <ø> (ø)
form/storage/istorage.hpp	100.00% <ø> (ø)
form/storage/storage.hpp	100.00% <ø> (ø)
... and 5 more

... and 8 files with indirect coverage changes

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[knoepfel]

Changes look good to me, @pcanal. I defer to @gemmeren and @barnaliy for their comments on the FORM changes.

[pcanal]

@gemmeren @aolivier23 @barnaliy Could you review this PR ? Thanks.

[barnaliy]

@pcanal : This is a clean improvement - eliminating the manual type map makes the API much simpler. I particularly like the use of DemangleName(). Thanks for doing all this work!

[gemmeren]

Thanks Philippe,
no objections, nut FORM will have to support non-ROOT backends, w/o DemangleName...

[aolivier23]

@gemmeren @pcanal @barnaliy Boost has a name demangler that doesn't depend on ROOT. It comes for free with something else phlex is using and seems to work with ROOT. Here's some documentation I quickly found: https://www.boost.org/doc/libs/latest/libs/core/doc/html/core/demangle.html

Will take a look at the PR tomorrow if it's not already merged. But sounds like great work!

[aolivier23]

The interface update looks good.

I think this will work with an eventual RNTuple backend but makes that a little more difficult. We have been using ROOT::RFieldBase::Create() when writing in the prototype, and that doesn't work with std::type_info as of writing. I think I see how to go through two steps using TClass to get a type name string using std::type_info. Or I could fall back to TClassEdit (or Boost) like you do.

std::type_info looks like it will work fine in reading mode. RNTupleReader::GetView() already has a std::type_info interface in the ROOT 6.36 documentation.

[pcanal]

I think I see how to go through two steps using TClass to get a type name string using std::type_info

This is the safest but you should also reach out to the RNTuple developer about the potentially missing interface (i.e. taking the type_info directly)