test: use -stdin for large rpc commands

Because of the MAX_ARG_STRLEN limit (128kb on most systems)
for args, these would usually fail. As a workaround, use
-stdin for these large calls. Idea by 0xB10C.

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

test/functional/test_framework/test_node.py

@@ -46,6 +46,8 @@ BITCOIND_PROC_WAIT_TIMEOUT = 60
 # The size of the blocks xor key
 # from InitBlocksdirXorKey::xor_key.size()
 NUM_XOR_BYTES = 8
+CLI_MAX_ARG_SIZE = 131071 # many systems have a 128kb limit per arg (MAX_ARG_STRLEN)
+
 # The null blocks key (all 0s)
 NULL_BLK_XOR_KEY = bytes([0] * NUM_XOR_BYTES)
 BITCOIN_PID_FILENAME_DEFAULT = "bitcoind.pid"
@@ -920,12 +922,24 @@ class TestNodeCLI():
         p_args = self.binaries.rpc_argv() + [f"-datadir={self.datadir}"] + self.options
         if named_args:
             p_args += ["-named"]
+        base_arg_pos = len(p_args)
         if clicommand is not None:
             p_args += [clicommand]
         p_args += pos_args + named_args
+        max_arg_size = max(len(arg) for arg in p_args)
+        stdin_data = self.input
+        if max_arg_size > CLI_MAX_ARG_SIZE:
+            self.log.debug(f"Cli: Command size {max_arg_size} too large, using stdin")
+            rpc_args = "\n".join([arg for arg in p_args[base_arg_pos:]])
+            if stdin_data is not None:
+                stdin_data += "\n" + rpc_args
+            else:
+                stdin_data = rpc_args
+            p_args = p_args[:base_arg_pos] + ['-stdin']
+
         self.log.debug("Running bitcoin-cli {}".format(p_args[2:]))
         process = subprocess.Popen(p_args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
-        cli_stdout, cli_stderr = process.communicate(input=self.input)
+        cli_stdout, cli_stderr = process.communicate(input=stdin_data)
         returncode = process.poll()
         if returncode:
             match = re.match(r'error code: ([-0-9]+)\nerror message:\n(.*)', cli_stderr)