Merge pull request #67 from scipp/importable-mantidio

Importable mantidio
scipp · Feb 1, 2024 · b912f2f · b912f2f
2 parents 7d4847d + 9fad2f7
commit b912f2f
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Showing 2 changed files with 33 additions and 13 deletions.
diff --git a/src/esssans/isis/io.py b/src/esssans/isis/io.py
@@ -42,12 +42,14 @@ def read_xml_detector_masking(
 
     The format is as follows, where the detids are inclusive ranges of detector IDs:
 
-    <?xml version="1.0"?>
-    <detector-masking>
-        <group>
-            <detids>1400203-1400218,1401199,1402190-1402223</detids>
-        </group>
-    </detector-masking>
+    .. code-block:: xml
+
+        <?xml version="1.0"?>
+        <detector-masking>
+            <group>
+                <detids>1400203-1400218,1401199,1402190-1402223</detids>
+            </group>
+        </detector-masking>
 
     Parameters
     ----------

diff --git a/src/esssans/isis/mantidio.py b/src/esssans/isis/mantidio.py
@@ -3,13 +3,11 @@
 """
 File loading functions for ISIS data using Mantid.
 """
-from typing import NewType
+from typing import NewType, NoReturn
 
 import sciline
 import scipp as sc
 import scippneutron as scn
-from mantid.api import MatrixWorkspace, Workspace
-from mantid.simpleapi import CopyInstrumentParameters, Load
 from scipp.constants import g
 
 from ..types import (
@@ -21,6 +19,24 @@
 )
 from .io import CalibrationFilename, Filename, FilePath
 
+try:
+    import mantid.api as _mantid_api
+    import mantid.simpleapi as _mantid_simpleapi
+    from mantid.api import MatrixWorkspace
+except ModuleNotFoundError:
+    # Catch runtime usages of Mantid
+    class _MantidFallback:
+        def __getattr__(self, name: str) -> NoReturn:
+            raise ImportError(
+                'Mantid is required to use `sans.isis.mantidio` ' 'but is not installed'
+            ) from None
+
+    _mantid_api = _MantidFallback()
+    _mantid_simpleapi = _MantidFallback
+    # Needed for type annotations
+    MatrixWorkspace = object
+
+
 CalibrationWorkspace = NewType('CalibrationWorkspace', MatrixWorkspace)
 
 
@@ -47,7 +63,7 @@ def get_detector_ids(ws: DataWorkspace[SampleRun]) -> sc.Variable:
 
 
 def load_calibration(filename: FilePath[CalibrationFilename]) -> CalibrationWorkspace:
-    ws = Load(Filename=str(filename), StoreInADS=False)
+    ws = _mantid_simpleapi.Load(Filename=str(filename), StoreInADS=False)
     return CalibrationWorkspace(ws)
 
 
@@ -66,7 +82,7 @@ def from_data_workspace(
     ws: DataWorkspace[RunType],
     calibration: CalibrationWorkspace,
 ) -> LoadedFileContents[RunType]:
-    CopyInstrumentParameters(
+    _mantid_simpleapi.CopyInstrumentParameters(
         InputWorkspace=calibration, OutputWorkspace=ws, StoreInADS=False
     )
     up = ws.getInstrument().getReferenceFrame().vecPointingUp()
@@ -78,8 +94,10 @@ def from_data_workspace(
 
 
 def load_run(filename: FilePath[Filename[RunType]]) -> DataWorkspace[RunType]:
-    loaded = Load(Filename=str(filename), LoadMonitors=True, StoreInADS=False)
-    if isinstance(loaded, Workspace):
+    loaded = _mantid_simpleapi.Load(
+        Filename=str(filename), LoadMonitors=True, StoreInADS=False
+    )
+    if isinstance(loaded, _mantid_api.Workspace):
         # A single workspace
         data_ws = loaded
     else: