Apply suggestions: style and legacy control data protection

Co-authored-by: Philipp Schmidt <philipp.schmidt@xfel.eu>

src/exdf/write/sd_writer.py

@@ -119,7 +119,8 @@ class SourceDataWriter:
             after_base = perf_counter()
 
             self.write_control(
-                f, [sd for sd in sources if sd.is_control])
+                f, [sd for sd in sources
+                    if sd.is_control and not sd.is_legacy])
             after_control = perf_counter()
 
             self.write_instrument(
@@ -180,8 +181,8 @@ class SourceDataWriter:
             instrument_src = f.create_instrument_source(source)
             instrument_src.create_index(**index_group_counts)
 
-        for source in legacy_sources:
-            f.create_legacy_source(source.source, source.canonical_name)
+        for sd in legacy_sources:
+            f.create_legacy_source(sd.source, sd.canonical_name)
 
     def write_control(self, f, sources):
         """Write CONTROL and RUN data.
@@ -480,15 +481,18 @@ def build_sources_index(sources):
 def get_legacy_sources(sources):
     legacy_sources = []
     channels = []
-    for source in sources:
-        if not source.is_legacy:
+    for sd in sources:
+        if not sd.is_legacy:
             continue
-        legacy_sources.append(source)
-        if source.source.endswith(":xtdf"):
-            channels.append(source.source + "/image")
+        if sd.is_control:
+            raise ValueError(
+                "Legacy source name is not supported for CONTROL data")
+        legacy_sources.append(sd)
+        if sd.source.endswith(":xtdf"):
+            channels.append(sd.source + "/image")
         else:
             channels.extend(
-                (f"{source.source}/{grp}" in source.index_groups))
+                (f"{sd.source}/{grp}" for grp in sd.index_groups))
     return legacy_sources, channels