[MRG] better handle some pickfile errors

src/sourmash/picklist.py

@@ -1,5 +1,6 @@
 "Picklist code for extracting subsets of signatures."
 import csv
+import os
 from enum import Enum
 
 # set up preprocessing functions for column stuff
@@ -143,18 +144,23 @@ def load(self, pickfile, column_name):
         "load pickset, return num empty vals, and set of duplicate vals."
         pickset = self.init()
 
+        if not os.path.exists(pickfile) or not os.path.isfile(pickfile):
+            raise ValueError(f"pickfile '{pickfile}' must exist and be a regular file")
+
         n_empty_val = 0
         dup_vals = set()
         with open(pickfile, newline='') as csvfile:
             x = csvfile.readline()
 
             # skip leading comment line in case there's a manifest header
-            if x[0] == '#':
+            if not x or x[0] == '#':
                 pass
             else:
                 csvfile.seek(0)
 
             r = csv.DictReader(csvfile)
+            if not r.fieldnames:
+                raise ValueError(f"empty or improperly formatted pickfile '{pickfile}'")
 
             if column_name not in r.fieldnames:
                 raise ValueError(f"column '{column_name}' not in pickfile '{pickfile}'")

src/sourmash/sourmash_args.py

@@ -126,15 +126,15 @@ def load_picklist(args):
     if args.picklist:
         try:
             picklist = SignaturePicklist.from_picklist_args(args.picklist)
+
+            notify(f"picking column '{picklist.column_name}' of type '{picklist.coltype}' from '{picklist.pickfile}'")
+
+            n_empty_val, dup_vals = picklist.load(picklist.pickfile, picklist.column_name)
         except ValueError as exc:
             error("ERROR: could not load picklist.")
             error(str(exc))
             sys.exit(-1)
 
-        notify(f"picking column '{picklist.column_name}' of type '{picklist.coltype}' from '{picklist.pickfile}'")
-
-        n_empty_val, dup_vals = picklist.load(picklist.pickfile, picklist.column_name)
-
         notify(f"loaded {len(picklist.pickset)} distinct values into picklist.")
         if n_empty_val:
             notify(f"WARNING: {n_empty_val} empty values in column '{picklist.column_name}' in picklist file")

tests/test_cmd_signature.py

@@ -1627,6 +1627,45 @@ def test_sig_extract_7_no_ksize(c):
     assert len(siglist) == 3
 
 
+def test_sig_extract_8_empty_picklist_fail(runtmp):
+    # what happens with an empty picklist?
+    sig47 = utils.get_test_data('47.fa.sig')
+    sig63 = utils.get_test_data('63.fa.sig')
+
+    # make empty picklist
+    picklist_csv = runtmp.output('pick.csv')
+    with open(picklist_csv, 'w', newline='') as csvfp:
+        pass
+
+    picklist_arg = f"{picklist_csv}:md5full:md5"
+
+    with pytest.raises(SourmashCommandFailed):
+        runtmp.sourmash('sig', 'extract', sig47, sig63, '--picklist', picklist_arg)
+
+    err = runtmp.last_result.err
+    print(err)
+
+    assert "empty or improperly formatted pickfile" in err
+
+
+def test_sig_extract_8_nofile_picklist_fail(runtmp):
+    # what happens when picklist file does not exist?
+    sig47 = utils.get_test_data('47.fa.sig')
+    sig63 = utils.get_test_data('63.fa.sig')
+
+    # picklist file does not exist
+    picklist_csv = runtmp.output('pick.csv')
+    picklist_arg = f"{picklist_csv}:md5full:md5"
+
+    with pytest.raises(SourmashCommandFailed):
+        runtmp.sourmash('sig', 'extract', sig47, sig63, '--picklist', picklist_arg)
+
+    err = runtmp.last_result.err
+    print(err)
+
+    assert "must exist and be a regular file" in err
+
+
 def test_sig_extract_8_picklist_md5(runtmp):
     # extract 47 from 47, using a picklist w/full md5
     sig47 = utils.get_test_data('47.fa.sig')