[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

lldb/examples/python/crashlog.py

@@ -415,8 +415,14 @@ def parse(self):
         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)

lldb/test/Shell/ScriptInterpreter/Python/Crashlog/json.test

@@ -1,8 +1,13 @@
 # RUN: %clang_host -g %S/Inputs/test.c -o %t.out
+
 # RUN: cp %S/Inputs/a.out.ips %t.crash
 # RUN: python %S/patch-crashlog.py --binary %t.out --crashlog %t.crash --offsets '{"main":20, "bar":9, "foo":16}' --json
 # RUN: %lldb %t.out -o 'command script import lldb.macosx.crashlog' -o 'crashlog %t.crash' 2>&1 | FileCheck %s
 
+# RUN: cp %S/Inputs/a.out.ips %t.nometadata.crash
+# RUN: python %S/patch-crashlog.py --binary %t.out --crashlog %t.nometadata.crash --offsets '{"main":20, "bar":9, "foo":16}' --json --no-metadata
+# RUN: %lldb %t.out -o 'command script import lldb.macosx.crashlog' -o 'crashlog %t.nometadata.crash' 2>&1 | FileCheck %s
+
 # CHECK: Thread[0] Crashing Thread Name EXC_BAD_ACCESS (SIGSEGV) (KERN_INVALID_ADDRESS at 0x0000000000000000)
 # CHECK: [  0] {{.*}}out`foo + 16 at test.c
 # CHECK: [  1] {{.*}}out`bar + 8 at test.c

lldb/test/Shell/ScriptInterpreter/Python/Crashlog/patch-crashlog.py

@@ -49,13 +49,17 @@ def patch_addresses(self):
                     self.data = self.data.replace(
                         "@{}@".format(symbol), str(representation(patch_addr)))
 
+    def remove_metadata(self):
+        self.data= self.data[self.data.index('\n') + 1:]
+
 
 if __name__ == '__main__':
     parser = argparse.ArgumentParser(description='Crashlog Patcher')
     parser.add_argument('--binary', required=True)
     parser.add_argument('--crashlog', required=True)
     parser.add_argument('--offsets', required=True)
     parser.add_argument('--json', default=False, action='store_true')
+    parser.add_argument('--no-metadata', default=False, action='store_true')
     args = parser.parse_args()
 
     offsets = json.loads(args.offsets)
@@ -68,5 +72,8 @@ def patch_addresses(self):
     p.patch_uuid()
     p.patch_addresses()
 
+    if args.no_metadata:
+        p.remove_metadata()
+
     with open(args.crashlog, 'w') as file:
         file.write(p.data)