STEP/GMSH: exported step model is scaled after gmsh meshing

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Problem description

Exported step model is scaled by 1000 after gmsh meshing, when both are used in the same python session.

The following code imports some FreeCAD model, exports it to STEP format, meshes it in GMSH and then repeats the process (part of workflow for automated geometry optimization).

The file is exported scaled by 1000 after GMSH mesh generation. After session reset, file scale is back to normal.

Setting Part.exportUnits to different value does not help the situation.

import FreeCAD
import Import
import Part
import gmsh
import gc

def show_line(file, start):
    with open(file, 'r') as f:
        for line in f.readlines():
            if line.startswith(start):
                print(line)
                break


doc = FreeCAD.openDocument('/usr/local/share/examples/PartDesignExample.FCStd')
body = doc.findObjects(Type='PartDesign::Body')[0]

Part.exportUnits('MM')
Import.export([body], '/tmp/out.step')
FreeCAD.closeDocument(doc.Name)
del body
del doc
gc.collect()

# inspect some point coordinates
show_line('/tmp/out.step', '#25 =')

gmsh.initialize()
gmsh.option.setString('Geometry.OCCTargetUnit', 'M')
gmsh.model.add('model')
gmsh.merge('/tmp/out.step')
gmsh.model.mesh.generate(2)
gmsh.write('/tmp/out.msh')
gmsh.finalize()

doc = FreeCAD.openDocument('/usr/local/share/examples/PartDesignExample.FCStd')
body = doc.findObjects(Type='PartDesign::Body')[0]

Part.exportUnits('MM')
Import.export([body], '/tmp/out.step')
FreeCAD.closeDocument(doc.Name)

# inspect the same point coordinates
show_line('/tmp/out.step', '#25 =')

Full version info

Discovered in Debian packaged v0.20.2, reproduced in build from source v1.0.0 and latest main branch commit

Subproject(s) affected?

Other (specify in description)

Anything else?

Issue is not present in ImportGui

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