trx_toolkit/data_dump.py: fix return value of parse_msg()

Jenkins build #2516 has uncovered a problem in DATADumpFile.parse_msg():

  ======================================================================
  FAIL: test_parse_empty (test_data_dump.DATADump_Test)
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/build/src/target/trx_toolkit/test_data_dump.py",
         line 138, in test_parse_empty
      self.assertEqual(msg, False)
  AssertionError: None != False

I did a quick investigation, and figured out that this failure
happens when trying to call parse_msg() with idx == 0, because
DATADumpFile._seek2msg() basically does nothing in this case
and thus always returns True. The None itself comes from
DATADumpFile._parse_msg().

Let's ensure that DATADumpFile.parse_msg() always returns None,
even if DATADumpFile._seek2msg() fails. Also, update the unit
test, so we always test a wide range of 'idx' values.

Change-Id: Ifcfa9c5208636a0f9309f5ba8e47d282dc6a03f4

2 files changed, 6 insertions, 6 deletions

diff --git a/src/target/trx_toolkit/data_dump.py b/src/target/trx_toolkit/data_dump.py
index 7c5452bf..41af6950 100644
--- a/src/target/trx_toolkit/data_dump.py
+++ b/src/target/trx_toolkit/data_dump.py
@@ -158,14 +158,14 @@ class DATADumpFile(DATADump):
 	# Parses a particular message defined by index idx
 	# Return value:
 	#   a parsed message in case of success,
-	#   or None in case of EOF or header parsing error,
-	#   or False in case of message parsing error or out of range.
+	#   or None in case of EOF, out of range, or header parsing error,
+	#   or False in case of message parsing error.
 	def parse_msg(self, idx):
 		# Move descriptor to the beginning of requested message
 		rc = self._seek2msg(idx)
 		if not rc:
 			log.error("Couldn't find requested message")
-			return False
+			return None
 
 		# Attempt to parse a message
 		return self._parse_msg()
diff --git a/src/target/trx_toolkit/test_data_dump.py b/src/target/trx_toolkit/test_data_dump.py
index 2f7e25a0..51291967 100644
--- a/src/target/trx_toolkit/test_data_dump.py
+++ b/src/target/trx_toolkit/test_data_dump.py
@@ -133,9 +133,9 @@ class DATADump_Test(unittest.TestCase):
 
 	def test_parse_empty(self):
 		with self.assertLogs(level = 'ERROR'):
-			idx = random.randrange(100)
-			msg = self._ddf.parse_msg(idx)
-			self.assertEqual(msg, False)
+			for idx in range(100):
+				msg = self._ddf.parse_msg(idx)
+				self.assertEqual(msg, None)
 
 	def test_parse_all_empty(self):
 		msg_list = self._ddf.parse_all()