Use @ml-evs's trick with adapter dependencies

If an adapter dependency is not installed, a new type will be created
with the same name.
This is done for the sake of the docs.

In order to still warn and return about the non-existent dependency,
when trying to convert an OPTIMADE entry resource, the string
"optimade.adapters" is searched for in the representation of the "new"
type created.
This is because the new type will show up as belonging to the file in
which is was created.
This depends on a dependency never coming from within
"optimade.adapters", which makes sense, since it will always be external
libraries and packages.

optimade/adapters/structures/aiida.py

@@ -16,7 +16,7 @@
 except (ImportError, ModuleNotFoundError):
     from warnings import warn
 
-    StructureData = None
+    StructureData = type("StructureData", (), {})
     AIIDA_NOT_FOUND = (
         "AiiDA not found, cannot convert structure to an AiiDA StructureData"
     )
@@ -35,7 +35,7 @@ def get_aiida_structure_data(optimade_structure: OptimadeStructure) -> Structure
         AiiDA `StructureData` Node.
 
     """
-    if globals().get("StructureData", None) is None:
+    if "optimade.adapters" in repr(globals().get("StructureData")):
         warn(AIIDA_NOT_FOUND)
         return None
 

optimade/adapters/structures/ase.py

@@ -19,7 +19,7 @@
 try:
     from ase import Atoms, Atom
 except (ImportError, ModuleNotFoundError):
-    Atoms = None
+    Atoms = type("Atoms", (), {})
     ASE_NOT_FOUND = "ASE not found, cannot convert structure to an ASE Atoms"
 
 
@@ -39,7 +39,7 @@ def get_ase_atoms(optimade_structure: OptimadeStructure) -> Atoms:
         ASE `Atoms` object.
 
     """
-    if globals().get("Atoms", None) is None:
+    if "optimade.adapters" in repr(globals().get("Atoms")):
         warn(ASE_NOT_FOUND)
         return None
 

optimade/adapters/structures/cif.py

@@ -31,7 +31,7 @@
 except ImportError:
     from warnings import warn
 
-    np = None
+    np = type("np", (), {})
     NUMPY_NOT_FOUND = "NumPy not found, cannot convert structure to CIF"
 
 
@@ -51,7 +51,7 @@ def get_cif(  # pylint: disable=too-many-locals,too-many-branches
 
     """
     # NumPy is needed for calculations
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
         warn(NUMPY_NOT_FOUND)
         return None
 

optimade/adapters/structures/jarvis.py

@@ -18,7 +18,7 @@
 try:
     from jarvis.core.atoms import Atoms
 except (ImportError, ModuleNotFoundError):
-    Atoms = None
+    Atoms = type("Atoms", (), {})
     JARVIS_NOT_FOUND = "jarvis-tools package not found, cannot convert structure to a JARVIS Atoms. Visit https://github.com/usnistgov/jarvis"
 
 
@@ -38,7 +38,7 @@ def get_jarvis_atoms(optimade_structure: OptimadeStructure) -> Atoms:
         A jarvis `Atoms` object.
 
     """
-    if globals().get("Atoms", None) is None:
+    if "optimade.adapters" in repr(globals().get("Atoms")):
         warn(JARVIS_NOT_FOUND)
         return None
 

optimade/adapters/structures/proteindatabank.py

@@ -28,7 +28,7 @@
 except ImportError:
     from warnings import warn
 
-    np = None
+    np = type("np", (), {})
     NUMPY_NOT_FOUND = "NumPy not found, cannot convert structure to your desired format"
 
 from optimade.models import Species as OptimadeStructureSpecies
@@ -60,7 +60,7 @@ def get_pdbx_mmcif(  # pylint: disable=too-many-locals
         A modern PDBx/mmCIF file as a single Python `str` object.
 
     """
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
         warn(NUMPY_NOT_FOUND)
         return None
 

optimade/adapters/structures/pymatgen.py

@@ -18,8 +18,8 @@
 except (ImportError, ModuleNotFoundError):
     from warnings import warn
 
-    Structure = None
-    Molecule = None
+    Structure = type("Structure", (), {})
+    Molecule = type("Molecule", (), {})
     PYMATGEN_NOT_FOUND = "Pymatgen not found, cannot convert structure to a pymatgen Structure or Molecule"
 
 
@@ -46,7 +46,7 @@ def get_pymatgen(optimade_structure: OptimadeStructure) -> Union[Structure, Mole
         OPTIMADE structure.
 
     """
-    if globals().get("Structure", None) is None:
+    if "optimade.adapters" in repr(globals().get("Structure")):
         warn(PYMATGEN_NOT_FOUND)
         return None
 

optimade/adapters/structures/utils.py

@@ -12,7 +12,7 @@
 except ImportError:
     from warnings import warn
 
-    np = None
+    np = type("np", (), {})
     NUMPY_NOT_FOUND = "NumPy not found, cannot convert structure to your desired format"
 
 
@@ -32,7 +32,8 @@ def scaled_cell(
         A scaled 3x3 cell.
 
     """
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
+        print(repr(globals().get("np")))
         warn(NUMPY_NOT_FOUND)
         return None
 
@@ -65,7 +66,7 @@ def fractional_coordinates(
         A list of fractional coordinates for the atomic positions.
 
     """
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
         warn(NUMPY_NOT_FOUND)
         return None
 
@@ -104,7 +105,7 @@ def cell_to_cellpar(
         The unit cell parameters as a `list` of `float` values.
 
     """
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
         warn(NUMPY_NOT_FOUND)
         return None
 
@@ -137,7 +138,7 @@ def unit_vector(x: Vector3D) -> Vector3D:
         A unit vector in the same direction as `x`.
 
     """
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
         warn(NUMPY_NOT_FOUND)
         return None
 
@@ -191,7 +192,7 @@ def cellpar_to_cell(
         [`lattice_vectors`][optimade.models.structures.StructureResourceAttributes.lattice_vectors] attribute.
 
     """
-    if globals().get("np", None) is None:
+    if "optimade.adapters" in repr(globals().get("np")):
         warn(NUMPY_NOT_FOUND)
         return None