[BUG] Cannot change the mesh between 2 runs of the same 1D simulation

[RemDelaporteMathurin]

Describe the bug

Running a 1D sim, then changing the mesh, and running the sim again (after re-initialising) crashes.

To Reproduce

import festim as F
import numpy as np

my_model = F.HydrogenTransportProblem()

my_model.mesh = F.Mesh1D(vertices=np.linspace(0, 1, 100))

mat = F.Material(D_0=1e-4, E_D=0)

vol = F.VolumeSubdomain1D(id=1, material=mat, borders=[0, 1])

left = F.SurfaceSubdomain1D(id=1, x=0)
right = F.SurfaceSubdomain1D(id=2, x=1)

my_model.subdomains = [left, right, vol]

H = F.Species("H")
my_model.species = [H]

my_model.temperature = 400

my_model.boundary_conditions = [
    F.FixedConcentrationBC(subdomain=left, value=1.0, species=H),
    F.FixedConcentrationBC(subdomain=right, value=1.0, species=H),
]

my_model.settings = F.Settings(atol=1e-10, rtol=1e-10, transient=False)

my_model.initialise()
my_model.run()

print(my_model.facet_meshtags)

print("First run done")

my_model.volume_meshtags = None
my_model.facet_meshtags = None
my_model.mesh = F.Mesh1D(vertices=np.linspace(0, 1, 1000))


my_model.initialise()
print(my_model.facet_meshtags)

my_model.run()

Not setting the meshtags to None produces another error, setting them to none makes the solver not converge

[RemDelaporteMathurin]

This is because my_model.bc_forms isn't cleaned after calling initialise()!

my_model.initialise()
my_model.run()

print("First run done")
print(my_model.bc_forms)

my_model.volume_meshtags = None
my_model.facet_meshtags = None
my_model.mesh = F.Mesh1D(vertices=np.linspace(0, 1, 1000))


my_model.initialise()
print(my_model.bc_forms)

my_model.run()

print("Second run done")

Produces

First run done
[<dolfinx.fem.bcs.DirichletBC object at 0x727edcfc3770>, <dolfinx.fem.bcs.DirichletBC object at 0x727edcffa210>]
[<dolfinx.fem.bcs.DirichletBC object at 0x727edcfc3770>, <dolfinx.fem.bcs.DirichletBC object at 0x727edcffa210>, <dolfinx.fem.bcs.DirichletBC object at 0x727edcffa0d0>, <dolfinx.fem.bcs.DirichletBC object at 0x727edcfbafd0>]

[RemDelaporteMathurin]

Manually setting:

my_model.volume_meshtags = None
my_model.facet_meshtags = None
my_model.bc_forms = []

Fixes it!