[search] handle no rows and invalid regex

visidata/movement.py

@@ -6,6 +6,7 @@
 
 def rotateRange(n, idx, reverse=False):
     'Wraps an iter starting from idx. Yields indices from idx to n and then 0 to idx.'
+    if n == 0: return []
     if reverse:
         rng = range(idx-1, -1, -1)
         rng2 = range(n-1, idx-1, -1)

visidata/search.py

@@ -35,7 +35,12 @@ def findMatchingColumn(sheet, row, columns, func):
             if regex_flags is None:
                 regex_flags = sheet.options.regex_flags  # regex_flags defined in features.regex
             flagbits = sum(getattr(re, f.upper()) for f in regex_flags)
-            vd.searchContext["regex"] = re.compile(regex, flagbits) or vd.error('invalid regex: %s' % regex)
+            try:
+                compiled_re = re.compile(regex, flagbits)
+            except re.error as e:
+                vd.searchContext["regex"] = None  # make future calls to search-next fail
+                vd.error('invalid regex: %s' % e.msg)
+            vd.searchContext["regex"] = compiled_re
 
         regex = vd.searchContext.get("regex") or vd.fail("no regex")