Incorrect resolving of relative paths for DiskOnlyFileModel

[hboisgon]

Describe the bug
Parsing relative paths within hydrolib`-core does not seem to work properly.
This happens to InifielFieldModel and seems to be the case since the change to DiskOnlyFileModel.

Maybe related but when initialising a FMModel from a dictionnary with existing file links relative to the mdu file from a working directory that is different from the mdu file directory, hydrolib-core returns an error that files are not found.

To Reproduce
We see this with hydromt.
Example working dir is D: and files are written in:

• D:/dflow_model
  • dflowfm
    • dflowfm.mdu
    • fieldfile.ini
  • maps
    • dem.tif

If the inifiledmodel.initial.datafile.filepath.name is then relative to mdu: ../maps/dem.tif, the .. will be wrongfully parsed and changed in the mdu file so the file is not found anymore.

Example code to reproduce outside of HydroMT, in a small test:

def test_435_a():
    workdir = Path(r"d:\dam_ar\dflowfm_models\hydrolib-core-435")

    mdupath = workdir / r"dflow_model\dflowfm\dflowfm.mdu"
    mdupath_export = workdir / r"dflow_model_export\dflowfm\dflowfm.mdu"

    cwd = os.getcwd()
    os.chdir(os.path.dirname(mdupath))

    fmmodel = FMModel(mdupath)
    print(fmmodel.geometry.inifieldfile.initial) # will reveal paths that start with "dflowfm_model/", so relative path is wrong.

    fmmodel.filepath = mdupath_export
    fmmodel.save(recurse=True) # Will save MDU and inifield file, but with wrong references to non-existent tif and 1dfield ini file.

Work-around in hydromt is:

# Assign initial fields to model and write
inifield_model = IniFieldModel(initial=inilist, parameter=paramlist)
# FIXME: when initialising IniFieldModel hydrolib-core does not parse correclty the relative path
# For now re-update manually....
for i in range(len(inifield_model.initial)):
    path = Path(f"../maps/{inifield_model.initial[i].datafile.filepath.name}")
    inifield_model.initial[i].datafile.filepath = path
for i in range(len(inifield_model.parameter)):
    path = Path(f"../maps/{inifield_model.parameter[i].datafile.filepath.name}")
    inifield_model.parameter[i].datafile.filepath = path
# Write inifield file
inifield_model_filename = inifield_model._filename() + ".ini"
fm_dir = dirname(join(self.root, self._config_fn))
inifield_model.save(
    join(fm_dir, inifield_model_filename),
    recurse=False,
)

When initialising FMModel from D, with a dictionary that contains relative filepaths (eg "fieldfile.ini") to the mdu file in D/dlfow/dflowfm/dflowfm.mdu, then an error is returned that files are not found even if they do exist. Work-around is to temporary switch working dir to the mdu dir:

# Need to switch to dflowfm folder for files to be found and properly added
mdu_fn = cf_dict.pop("filepath", None)
cwd = os.getcwd()
os.chdir(dirname(mdu_fn))
mdu = FMModel(**cf_dict)
# add filepath
mdu.filepath = mdu_fn
# write
mdu.save(recurse=False)
# Go back to working dir
os.chdir(cwd)

Version info (please complete the following information):

• Version 0.1.3 dev

[priscavdsluis]

PR #512 will fix the problem for the greater part of the users.
We need to fix the root problem in another PR.