On write, update stop if it doesn't match last index

lasio/writer.py

@@ -104,13 +104,21 @@ def write(
         )
 
     # -------------------------------------------------------------------------
-    # TODO: recheck this, it hasn't been validated for the case of a new las
-    # file created by Lasio
+    # If an initial curve index was not read from a las file (las.index_initial)
+    # or the curve index has changed during processing
+    # or if the STOP value doesn't match the final index value
+    # then update the step variables before writing to a new las file object.
     # -------------------------------------------------------------------------
-    # if there is a curve index name and the index curve has changed
-    # then update the step variables
-    # -------------------------------------------------------------------------
-    if not (las.index_initial==las.index).all():  
+    index_changed = False
+    stop_is_different = False
+
+    if las.index_initial is not None:
+        index_changed = not (las.index_initial == las.index).all()
+        stop_is_different = las.index_initial[-1] != las.well.STOP.value
+    else:
+        index_changed = True
+
+    if index_changed or stop_is_different:
         las.update_start_stop_step(STRT, STOP, STEP)
 
     # Write each section.

tests/test_write.py

@@ -501,7 +501,7 @@ def test_write_single_step():
 ~Well ------------------------------------------------------
 STRT.M                  1670.0 : START DEPTH
 STOP.M                  1670.0 : STOP DEPTH
-STEP.M                       0 : STEP
+STEP.M                     0.0 : STEP
 NULL.                  -999.25 : NULL VALUE
 COMP.     ANY OIL COMPANY INC. : COMPANY
 WELL.                  AAAAA_2 : WELL