Fix traceback during songshowplus import. Fixes bug 1585489.

Fixes: https://launchpad.net/bugs/1585489

openlp/plugins/songs/lib/importers/songshowplus.py

@@ -116,7 +116,13 @@ class SongShowPlusImport(SongImport):
                     null, verse_name_length, = struct.unpack("BB", song_data.read(2))
                     verse_name = self.decode(song_data.read(verse_name_length))
                 length_descriptor_size, = struct.unpack("B", song_data.read(1))
-                log.debug(length_descriptor_size)
+                log.debug('length_descriptor_size: %d' % length_descriptor_size)
+                # In the case of song_numbers the number is in the data from the
+                # current position to the next block starts
+                if block_key == SONG_NUMBER:
+                    sn_bytes = song_data.read(length_descriptor_size - 1)
+                    self.song_number = int.from_bytes(sn_bytes, byteorder='little')
+                    continue
                 # Detect if/how long the length descriptor is
                 if length_descriptor_size == 12 or length_descriptor_size == 20:
                     length_descriptor, = struct.unpack("I", song_data.read(4))

tests/functional/openlp_plugins/songs/test_songshowplusimport.py

@@ -52,6 +52,8 @@ class TestSongShowPlusFileImport(SongImportTestHelper):
                          self.load_external_result_data(os.path.join(TEST_PATH, 'Beautiful Garden Of Prayer.json')))
         self.file_import([os.path.join(TEST_PATH, 'a mighty fortress is our god.sbsong')],
                          self.load_external_result_data(os.path.join(TEST_PATH, 'a mighty fortress is our god.json')))
+        self.file_import([os.path.join(TEST_PATH, 'cleanse-me.sbsong')],
+                         self.load_external_result_data(os.path.join(TEST_PATH, 'cleanse-me.json')))
 
 
 class TestSongShowPlusImport(TestCase):

tests/resources/songshowplussongs/cleanse-me.json

@@ -0,0 +1,38 @@
+{
+    "authors": [
+        "J. Edwin Orr"
+    ],
+    "ccli_number": 56307,
+    "comments": "",
+    "copyright": "Public Domain ",
+    "song_book_name": "",
+    "song_number": 438,
+    "title": "Cleanse Me [438]",
+    "topics": [
+        "Cleansing",
+        "Communion",
+        "Consecration",
+        "Holiness",
+        "Holy Spirit",
+        "Revival"
+    ],
+    "verse_order_list": [],
+    "verses": [
+        [
+            "Search me, O God,\r\nAnd know my heart today;\r\nTry me, O Savior,\r\nKnow my thoughts, I pray.\r\nSee if there be\r\nSome wicked way in me;\r\nCleanse me from every sin\r\nAnd set me free.",
+            "v1"
+        ],
+        [
+            "I praise Thee, Lord,\r\nFor cleansing me from sin;\r\nFulfill Thy Word,\r\nAnd make me pure within.\r\nFill me with fire\r\nWhere once I burned with shame;\r\nGrant my desire\r\nTo magnify Thy name.",
+            "v2"
+        ],
+        [
+            "Lord, take my life,\r\nAnd make it wholly Thine;\r\nFill my poor heart\r\nWith Thy great love divine.\r\nTake all my will,\r\nMy passion, self and pride;\r\nI now surrender, Lord\r\nIn me abide.",
+            "v3"
+        ],
+        [
+            "O Holy Ghost,\r\nRevival comes from Thee;\r\nSend a revival,\r\nStart the work in me.\r\nThy Word declares\r\nThou wilt supply our need;\r\nFor blessings now,\r\nO Lord, I humbly plead.",
+            "v4"
+        ]
+    ]
+}