[docs] update to Documenter@1 and Clang@0.19

[odow]

Description

This PR updates the documentation build to use Documenter@1 and Clang@0.19

Preview link: https://ergo-code.github.io/HiGHS/previews/PR3229/

Checklist

• I have read the contributing guidelines
• This PR targets the latest branch
• Tests are passing
• Documentation was updated where relevant
• This PR is not primarily AI-generated (per the AI contributions policy in CONTRIBUTING.md)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.21%. Comparing base (c32911c) to head (3750126).
⚠️ Report is 39 commits behind head on latest.

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3229      +/-   ##
==========================================
+ Coverage   73.15%   73.21%   +0.05%     
==========================================
  Files         445      445              
  Lines      108018   107993      -25     
  Branches    17313    17316       +3     
==========================================
+ Hits        79024    79069      +45     
+ Misses      28718    28648      -70     
  Partials      276      276              

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[filikat]

Thanks! Now it works (after updating Julia), but only if I compile from the HiGHS folder. If I compile from docs, it fails with LoadError: SystemError: opening file "docs/c_api_gen/libhighs.jl": No such file or directory. The path to libhighs.jl assumes that you are in the HiGHS folder, but the instructions in the README to compile the docs assume that you are in docs.

[jajhall]

Unless it's viewed as a breaking change, I wouldn't mind changing the documentation. Then building docs is done from the same place as building HiGHS and pip install

[odow]

This will now work from any directory. The README was also missing --project.

[filikat]

It works if I run just julia docs/make.jl. However, if I add --project=docs or I run julia --project=docs -e 'using Pkg; Pkg.instantiate()', I get the error

Failed to precompile Clang [40e3b903-d033-50b4-a0cc-940c62c95e31] to "/Users/filippozanetti/.julia/compiled/v1.12/Clang/jl_Pr8DMy".
ERROR: LoadError: UndefVarError: `libclang` not defined in `Clang.LibClang`
Suggestion: check for spelling errors or missing imports.
Stacktrace:
  [1] clang_getClangVersion
    @ ~/.julia/packages/Clang/kqsoL/lib/18/LibClang.jl:5835 [inlined]
  [2] version()
    @ Clang ~/.julia/packages/Clang/kqsoL/src/Clang.jl:77
  [3] top-level scope
    @ ~/.julia/packages/Clang/kqsoL/src/Clang.jl:84
  [4] include(mod::Module, _path::String)
    @ Base ./Base.jl:306
  [5] include_package_for_output(pkg::Base.PkgId, input::String, depot_path::Vector{String}, dl_load_path::Vector{String}, load_path::Vector{String}, concrete_deps::Vector{Pair{Base.PkgId, UInt128}}, source::Nothing)
    @ Base ./loading.jl:3106
  [6] top-level scope
    @ stdin:5
  [7] eval(m::Module, e::Any)
    @ Core ./boot.jl:489
  [8] include_string(mapexpr::typeof(identity), mod::Module, code::String, filename::String)
    @ Base ./loading.jl:2952
  [9] include_string
    @ ./loading.jl:2962 [inlined]
 [10] exec_options(opts::Base.JLOptions)
    @ Base ./client.jl:315
 [11] _start()
    @ Base ./client.jl:550

[odow]

Delete the Manifest.toml. You’ve got the old mix of versions installed. If it works without project it’s because you have something installed in your global project.

start julia --project=docs

then type ] to enter the package manager, st to see what versions are installed, update or resolve to update.

(base) odow@Mac HiGHS % julia --project=docs
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.12.7 (2026-08-15)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org release
|__/                   |

(docs) pkg> st
Status `~/git/ERGO-Code/HiGHS/docs/Project.toml`
  [40e3b903] Clang v0.19.3
  [e30172f5] Documenter v1.17.0

(docs) pkg> update
    Updating registry at `~/.julia/registries/General.toml`
     Project No packages added to or removed from `~/git/ERGO-Code/HiGHS/docs/Project.toml`
    Manifest No packages added to or removed from `~/git/ERGO-Code/HiGHS/docs/Manifest.toml`

(docs) pkg> 

[filikat]

Thanks, now everything works

[galabovaa]

LGTM!

[galabovaa]

Thank you!