[lldb] Improve meta data stripping from JSON crashlogs

JSON crashlogs normally start with a single line of meta data that we
strip unconditionally. Some producers started omitting the meta data
which tripped up crashlog. Be more resilient by only removing the first
line when we know it really is meta data.

rdar://82641662

1 files changed, 8 insertions, 2 deletions

diff --git a/lldb/examples/python/crashlog.py b/lldb/examples/python/crashlog.py
index e6d88a0..aec4096 100755
--- a/lldb/examples/python/crashlog.py
+++ b/lldb/examples/python/crashlog.py
@@ -415,8 +415,14 @@ class JSONCrashLogParser:
         with open(self.path, 'r') as f:
             buffer = f.read()
 
-        # First line is meta-data.
-        buffer = buffer[buffer.index('\n') + 1:]
+        # Skip the first line if it contains meta data.
+        head, _, tail = buffer.partition('\n')
+        try:
+            metadata = json.loads(head)
+            if 'app_name' in metadata and 'app_version' in metadata:
+                buffer = tail
+        except ValueError:
+            pass
 
         try:
             self.data = json.loads(buffer)