LanguageServer.jl/SymbolServer.jl fails to index this package

[rossviljoen]

When trying to run LanguageServer.jl in an environment containing this package, the following error occurs:

ERROR: LoadError: Failure to obtain a bits-type
Stacktrace:
  [1] error(s::String)
    @ Base ./error.jl:35
  [2] bitstype(::Type{CBinding.libclang.var"c\"struct CXVirtualFileOverlayImpl\""})
    @ CBinding ~/.julia/packages/CBinding/pvfFX/src/CBinding.jl:93
  [3] fields(::Type{CBinding.libclang.var"c\"struct CXVirtualFileOverlayImpl\""})
    @ CBinding ~/.julia/packages/CBinding/pvfFX/src/CBinding.jl:99
  [4] fieldnames(::Type{CBinding.libclang.var"c\"struct CXVirtualFileOverlayImpl\""})
    @ CBinding ~/.julia/packages/CBinding/pvfFX/src/aggregates.jl:34
  [5] fieldcount(::Type{CBinding.libclang.var"c\"struct CXVirtualFileOverlayImpl\""})
    @ CBinding ~/.julia/packages/CBinding/pvfFX/src/aggregates.jl:32
  [6] fieldcount(::Type{CBinding.Cptr{CBinding.libclang.var"c\"struct CXVirtualFileOverlayImpl\""}})
    @ CBinding ~/.julia/packages/CBinding/pvfFX/src/pointers.jl:64
  [7] Main.SymbolServer.DataTypeStore(t::Any, symbol::Symbol, parent_mod::Module, exported::Bool)
    @ Main.SymbolServer ~/.julia/packages/SymbolServer/2jiVV/src/symbols.jl:77
  [8] symbols(env::Dict{Symbol, Main.SymbolServer.ModuleStore}, m::Module, allnames::Base.IdSet{Symbol}, visited::Base.IdSet{Module}; get_return_type::Bool)
    @ Main.SymbolServer ~/.julia/packages/SymbolServer/2jiVV/src/symbols.jl:430
  [9] symbols
    @ ~/.julia/packages/SymbolServer/2jiVV/src/symbols.jl:419 [inlined]
 [10] symbols(env::Dict{Symbol, Main.SymbolServer.ModuleStore}, m::Nothing, allnames::Base.IdSet{Symbol}, visited::Base.IdSet{Module}; get_return_type::Bool)
    @ Main.SymbolServer ~/.julia/packages/SymbolServer/2jiVV/src/symbols.jl:479
 [11] symbols(env::Dict{Symbol, Main.SymbolServer.ModuleStore}, m::Nothing, allnames::Base.IdSet{Symbol}, visited::Base.IdSet{Module})
    @ Main.SymbolServer ~/.julia/packages/SymbolServer/2jiVV/src/symbols.jl:419
 [12] top-level scope
    @ ~/.julia/packages/SymbolServer/2jiVV/src/server.jl:119
in expression starting at /home/rviljoen/.julia/packages/SymbolServer/2jiVV/src/server.jl:1

failing because fieldcount(::Type{CBinding.Cptr{CBinding.libclang.var"c\"struct CXVirtualFileOverlayImpl\""}}) errors.

It's not clear to me if this is something that should be fixed in SymbolServer.jl or here

[rossviljoen]

Corresponding issue for the language server: julia-vscode/LanguageServer.jl#1095

[krrutkow]

This error occurs because in C, it is possible to have a pointer to an opaque struct or union where it doesn't have its fields defined (yet). So attempting to count/enumerate its fields results in an error until the type is fully defined. How does your package currently handle abstract types? Where fieldcount(...) usage errors with:

ERROR: ArgumentError: type does not have a definite number of fields

This scenario would be fairly similar to that one, I think.

[rossviljoen]

Thanks for the quick reply. The relevant expression in that package is:
isconcretetype(ur_t) && fieldcount(ur_t) > 0 ? collect(fieldnames(ur_t)) : Symbol[]

So, it assumes that a concrete type has fieldcount and fieldnames defined.
Would it be reasonable to have fieldcount return 0 until the fields are actually defined?

[krrutkow]

Yeah, that solution seems to work fine. I doubt there are any users relying on the error being thrown, so the change in behavior shouldn't be an issue.

[krrutkow]

@rossviljoen CBinding v1.1 was released with the fix, could you please see if it resolves this issue?

[rossviljoen]

That seems to have fixed it, thanks!