BUG: make to_ascii work with fasta files

Also add regression test. Previously, this function would fail with fasta files
because the call to qual.astype would fail (because qual is None when the
file is fasta)

Author: Adam Robbins-Pianka

qiita_ware/demux.py

@@ -438,7 +438,10 @@ def to_ascii(demux, samples=None):
     for samp, idx, seq, qual, bc_ori, bc_cor, bc_err in fetch(demux, samples):
         seq_id = id_fmt % {'sample': samp, 'idx': idx, 'bc_ori': bc_ori,
                            'bc_cor': bc_cor, 'bc_diff': bc_err}
-        yield formatter(seq_id, seq, qual.astype(np.uint8))
+        if qual is not None:
+            qual = qual.astype(np.uint8)
+
+        yield formatter(seq_id, seq, qual)
 
 
 def to_per_sample_ascii(demux, samples=None):

qiita_ware/test/test_demux.py

@@ -282,12 +282,29 @@ def test_to_ascii(self):
                                          delete=False) as f:
             f.write(fqdata)
 
-        exp = [(b"@a_0 orig_bc=abc new_bc=abc bc_diffs=0\nxyz\n+\nABC\n"),
-               (b"@b_0 orig_bc=abw new_bc=wbc bc_diffs=4\nqwe\n+\nDFG\n"),
-               (b"@b_1 orig_bc=abw new_bc=wbc bc_diffs=4\nqwe\n+\nDEF\n")]
         self.to_remove.append(f.name)
         to_hdf5(f.name, self.hdf5_file)
 
+        exp = [b"@a_0 orig_bc=abc new_bc=abc bc_diffs=0\nxyz\n+\nABC\n",
+               b"@b_0 orig_bc=abw new_bc=wbc bc_diffs=4\nqwe\n+\nDFG\n",
+               b"@b_1 orig_bc=abw new_bc=wbc bc_diffs=4\nqwe\n+\nDEF\n"]
+
+        obs = list(to_ascii(self.hdf5_file, samples=['a', 'b']))
+        self.assertEqual(obs, exp)
+
+    def test_to_ascii_fasta(self):
+        with tempfile.NamedTemporaryFile('r+', suffix='.fna',
+                                         delete=False) as f:
+            f.write(seqdata)
+
+        self.to_remove.append(f.name)
+        to_hdf5(f.name, self.hdf5_file)
+
+        exp = [b">a_0 orig_bc=abc new_bc=abc bc_diffs=0\nx\n",
+               b">a_1 orig_bc=aby new_bc=ybc bc_diffs=2\nxy\n",
+               b">a_2 orig_bc=abz new_bc=zbc bc_diffs=3\nxyz\n",
+               b">b_0 orig_bc=abx new_bc=xbc bc_diffs=1\nxyz\n",
+               b">b_1 orig_bc=abw new_bc=wbc bc_diffs=4\nabcd\n"]
 
         obs = list(to_ascii(self.hdf5_file, samples=['a', 'b']))
         self.assertEqual(obs, exp)