dev-splice: newline-separated script segments fail to compile via JSON-RPC #9553

Summary

dev-splice scripts with segments separated by real newlines (\n) fail to compile when submitted via JSON-RPC, even though doc/dev-splice.7.md states segments are "separated by newlines or semicolons" and is_delimiter() in common/splice_script.c accepts \n. The identical script with ; separators compiles and executes fine.

Reproduction

Over the raw JSON-RPC unix socket (bypassing lightning-cli and clnrest entirely):

Semicolon-separated — works:

{"jsonrpc":"2.0","id":1,"method":"dev-splice","params":{"script_or_json":"wallet -> 500000sat ; 500000sat -> <channel_id>","dryrun":true}}

{"dryrun":["wallet withdraw 500000sat","put 500000sat into <channel_id>","put 100% of rest into wallet"]}

Newline-separated — fails:

{"jsonrpc":"2.0","id":1,"method":"dev-splice","params":{"script_or_json":"wallet -> 500000sat\n500000sat -> <channel_id>","dryrun":true}}

{"code":-32602,"message":"Splice script compile failed","compiler_error":["Missing sat amount. A sat amount or '*' is required here","wallet -> 500000sat\\n500000sat -> <channel_id>","^","Compiler phase: validate_and_clean"]}

A variant with +fee fails differently (Failed to parse sat amount, Compiler phase: type_data), which suggests the newline is reaching parse_splice_script but not being tokenized as TOK_DELIMITER — the segment split never happens.

Same behavior via lightning-cli dev-splice -k script_or_json=$'...\n...' (real newline in argv).

Expected

Newline-separated segments compile identically to ;-separated ones, per the documented grammar.

Version

v26.06.8 (built from source, mainnet).

Secondary issue: clnrest drops compiler_error from error responses

When the same call fails through clnrest, the HTTP 500 body is only:

{"code":-32602,"data":null,"message":"Splice script compile failed"}

The compiler_error array (the actionable detail: reason + caret position + phase) is stripped, making splice script errors undebuggable via REST. Any extra keys on RPC error objects should be passed through.

Workaround

Use ; as the segment separator — works over JSON-RPC, clnrest, and CLI.