combine_experiments: Handle default max_clusters (dials#2311)

Prevent dials.combine_experiments from raising TypeError in cases
where clustering.use=True but the default clustering.max_clusters=None.

Instead, interpret max_clusters=None as requesting all of the clusters.

AUTHORS

@@ -6,6 +6,7 @@ Asmit Bhowmick
 Benjamin Williams
 Billy Poon
 Daniel Paley
+Daniel Tchon
 David Waterman
 Derek Mendez
 Graeme Winter

newsfragments/2311.bugfix

@@ -0,0 +1 @@
+``dials.combine_experiments``: Prevent default ``clustering.max_clusters=None`` from raising error when clustering.

src/dials/command_line/combine_experiments.py

@@ -745,16 +745,18 @@ def save_in_batches(
 
         # cluster the resulting experiments if requested
         if params.clustering.use and len(experiments) > 1:
+            if params.clustering.max_clusters == 0:
+                sys.exit("Error: max_clusters must be None or >0")
             clustered = do_unit_cell_clustering(
                 experiments,
                 reflections,
                 dendrogram=params.clustering.dendrogram,
                 threshold=params.clustering.threshold,
             )
             n_clusters = len(clustered)
-            clusters = sorted(clustered.clusters, key=len, reverse=True)[
-                : min(params.clustering.max_clusters, n_clusters)
-            ]
+            clusters = sorted(clustered.clusters, key=len, reverse=True)
+            if params.clustering.max_clusters is not None:
+                clusters = clusters[: params.clustering.max_clusters]
             if params.clustering.exclude_single_crystal_clusters:
                 clusters = [c for c in clusters if len(c) > 1]
             clustered_experiments = [