Error on using highs as solver

Start with the Model initialization in mip/model.py and the HiGHS loading and cleanup paths in mip/highs.py, which are named in the traceback. Reproduce the Python 3.11/3.12 Windows failures with highspy installed and inspect the expected library path and exported symbols. Done means the documented HiGHS setup works or the documentation clearly states the supported installation and configuration.

I have this code with python 3.11 and python 3.12:

import sys
print(sys.version_info)

from mip import Model, xsum, BINARY

# Create a model
model = Model(solver="highs")

# Add variables
x = [model.add_var(var_type=BINARY) for i in range(5)]

# Add constraints
model += xsum(x) <= 3
model += xsum(x) >= 1

# Set the objective
model.objective = xsum(x)

# Solve the model
model.optimize()

print("Objective:",model.objective_value)

# Check which solver was used
print(f"Solver used: {model.solver_name}")

I additionally installed highspy to be sure highs is available. Highs claims to be fastest open solver ;-) so I wanted to check this. On running I get error:

Traceback (most recent call last):
  File "C:\Users\...\Python\xlsb-test\solver_check.py", line 7, in <module>
    model = Model(solver="highs")
            ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\mip\model.py", line 111, in __init__
    self.constrs = mip.ConstrList(self)
                   ^^^
UnboundLocalError: cannot access local variable 'mip' where it is not associated with a value

Using

...
model = Model(solver_name=HIGHS)
...

results in

An error occurred while loading the HiGHS library:
not enough values to unpack (expected 1, got 0)
Traceback (most recent call last):
  File "C:\Users\...\Python\xlsb-test\solver_check.py", line 13, in <module>
    model = Model(solver_name=HIGHS)
            ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\di29394\AppData\Roaming\Python\Python312\site-packages\mip\model.py", line 97, in __init__
    self.solver = mip.highs.SolverHighs(self, name, sense)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\di29394\AppData\Roaming\Python\Python312\site-packages\mip\highs.py", line 690, in __init__
    raise FileNotFoundError(
FileNotFoundError: HiGHS not found.Please install the `highspy` package, orset the `PMIP_HIGHS_LIBRARY` environment variable.
Exception ignored in: <function SolverHighs.__del__ at 0x000001E57F5DE160>
Traceback (most recent call last):
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\mip\highs.py", line 728, in __del__
    self._lib.Highs_destroy(self._model)
    ^^^^^^^^^
AttributeError: 'SolverHighs' object has no attribute '_lib'

As I said, highspy is installed. Setting PMIP_HIGHS_LIBRARY to the highs.exe path results in

Traceback (most recent call last):
  File "C:\Users\...\Python\xlsb-test\solver_check.py", line 13, in <module>
    model = Model(solver_name=HIGHS)
            ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\mip\model.py", line 97, in __init__
    self.solver = mip.highs.SolverHighs(self, name, sense)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\mip\highs.py", line 703, in __init__
    self._model = highslib.Highs_create()
                  ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\cffi\api.py", line 914, in __getattr__
    make_accessor(name)
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\cffi\api.py", line 910, in make_accessor
    accessors[name](name)
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\cffi\api.py", line 840, in accessor_function
    value = backendlib.load_function(BType, name)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: function/symbol 'Highs_create' not found in library 'C:\ProgramData\SOLVERS\highs.exe': error 0x7f. Did you mean: 'Highs_clear'?
Exception ignored in: <function SolverHighs.__del__ at 0x000001B6481C6700>
Traceback (most recent call last):
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\mip\highs.py", line 728, in __del__
    self._lib.Highs_destroy(self._model)
    ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\cffi\api.py", line 914, in __getattr__
    make_accessor(name)
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\cffi\api.py", line 910, in make_accessor
    accessors[name](name)
  File "C:\Users\...\AppData\Roaming\Python\Python312\site-packages\cffi\api.py", line 840, in accessor_function
    value = backendlib.load_function(BType, name)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: function/symbol 'Highs_destroy' not found in library 'C:\ProgramData\SOLVERS\highs.exe': error 0x7f

So there seems to exist no way for activating highs. Maybe the docs should be updated with a highs example.