util: Show choices for volid if all are too long

When we fail to generate a volume ID that fits in 32 characters, the
error message should include the options that were considered. It could
show that there might be a substitution that could fix the problem.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

pungi/util.py

@@ -366,6 +366,7 @@ def get_volid(compose, arch, variant=None, escape_spaces=False, disc_type=False)
     else:
         all_products = products
 
+    tried = set()
     for i in all_products:
         if not variant_uid and "%(variant)s" in i:
             continue
@@ -384,9 +385,11 @@ def get_volid(compose, arch, variant=None, escape_spaces=False, disc_type=False)
         volid = _apply_substitutions(compose, volid)
         if len(volid) <= 32:
             break
+        tried.add(volid)
 
     if volid and len(volid) > 32:
-        raise ValueError("Could not create volume ID <= 32 characters")
+        raise ValueError("Could not create volume ID longer than 32 bytes, options are %r",
+                         sorted(tried, key=len))
 
     if volid and escape_spaces:
         volid = volid.replace(" ", r"\x20")

tests/test_util.py

@@ -158,6 +158,28 @@ class TestVolumeIdGenerator(unittest.TestCase):
 
             self.assertEqual(volid, expected)
 
+    @mock.patch('pungi.compose.ComposeInfo')
+    def test_get_volid_too_long(self, ci):
+        conf = {
+            'release_short': 'rel_short2',
+            'release_version': '6.0',
+            'release_is_layered': False,
+            'image_volid_formats': [
+                'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa',   # 34 chars
+                'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb',    # 33 chars
+            ],
+            'image_volid_layered_product_formats': [],
+            'volume_id_substitutions': {},
+        }
+        variant = mock.Mock(uid='Server', type='variant')
+        c = compose.Compose(conf, self.tmp_dir)
+
+        with self.assertRaises(ValueError) as ctx:
+            util.get_volid(c, 'x86_64', variant, escape_spaces=False, disc_type=False)
+
+        self.assertIn('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb', str(ctx.exception))
+        self.assertIn('aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa', str(ctx.exception))
+
 
 class TestFindOldCompose(unittest.TestCase):
     def setUp(self):