[Piglit] [PATCH 4/4] framework: Repair result file if test run is interrupted

[Chad Versace]

If the JSON result file was not closed properly, perhaps due a system
crash during a test run, then TestrunResult.parseFile will attempt to
repair the file before parsing it.

Signed-off-by: Chad Versace <chad at chad-versace.us>
---
 framework/core.py |   68 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/framework/core.py b/framework/core.py
index afc5a28..cbd3ef3 100644
--- a/framework/core.py
+++ b/framework/core.py
@@ -291,6 +291,68 @@ class TestrunResult:
 			raise ResultFileInOldFormatError(file.name)
 		file.seek(saved_position)
 
+	def __repairFile(self, file):
+		'''
+		Reapair JSON file if necessary
+
+		If the JSON file is not closed properly, perhaps due a system
+		crash during a test run, then the JSON is repaired by
+		discarding the trailing, incomplete item and appending braces
+		to the file to close the JSON object.
+
+		Warning: This sets the file's position to 0.
+		'''
+
+		file.seek(0)
+		lines = file.readlines()
+
+		if lines[-1] == '}':
+			# JSON object was closed properly. No repair is
+			# necessary.
+			file.seek(0)
+			return
+
+		# JSON object was not closed properly.
+		#
+		# To repair the file, we execute these steps:
+		#   1. Find the closing brace of the last, properly written
+		#      test result.
+		#   2. Discard all subsequent lines.
+		#   3. Remove the trailing comma of that test result.
+		#   4. Append enough closing braces to close the json object.
+		#   5. Replace file's contents with repaired JSON.
+
+		# Each non-terminal test result ends with this line:
+		safe_line =  3 * JSONWriter.INDENT * ' ' + '},\n'
+
+		# Search for the last occurence of safe_line.
+		safe_line_num = None
+		for i in range(-1, - len(lines), -1):
+			if lines[i] == safe_line:
+				safe_line_num = i
+				break
+
+		if safe_line_num is None:
+			raise Exception('failed to repair corrupt result file: ' + file.name)
+
+		# Remove corrupt lines.
+		lines = lines[0:(safe_line_num + 1)]
+
+		# Remove trailing comma.
+		lines[-1] = 3 * JSONWriter.INDENT * ' ' + '}\n'
+
+		# Close json object.
+		lines.append(JSONWriter.INDENT * ' ' + '}\n')
+		lines.append('}')
+
+		# Replace contents of corrupt file.
+		file.truncate(0)
+		file.seek(0)
+		file.writelines(lines)
+		file.flush()
+		os.fsync(file.fileno())
+		file.seek(0)
+
 	def write(self, file):
 		# Serialize only the keys in serialized_keys.
 		keys = set(self.__dict__.keys()).intersection(self.serialized_keys)
@@ -299,7 +361,7 @@ class TestrunResult:
 
 	def parseFile(self, file):
 		self.__checkFileIsNotInOldFormat(file)
-
+		self.__repairFile(file)
 		raw_dict = json.load(file)
 
 		# Check that only expected keys were unserialized.
@@ -510,7 +572,9 @@ def loadTestResults(path):
 
 	testrun = TestrunResult()
 	try:
-		with open(filepath, 'r') as file:
+		# Open the file in r+ mode so that it can be repaired if
+		# necessary.
+		with open(filepath, 'r+') as file:
 			testrun.parseFile(file)
 	except OSError:
 		traceback.print_exc()
-- 
1.7.6