refactor: separate response decoding from emission#554
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Each output-mode arm previously forked on `--json`, duplicating the "decode and stash vs. decode and print" logic. The recent `-o hex --json` double-printing bug was a direct consequence — easy to forget one of the `if !args.json` guards. Split the flow into a `decode_response` step that returns a `Decoded` enum (Candid / Text / Bytes) and a single emission step that forks on `--json` exactly once. Semantics are unchanged: `-o` still controls decoding strictness, `--json` still controls envelope vs. human output, and the two remain orthogonal. The write-vs-decode error reconciliation in JSON mode is preserved. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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* Don't print response in `-o hex --json` * changelog * refactor(canister call): separate response decoding from emission (#554) Each output-mode arm previously forked on `--json`, duplicating the "decode and stash vs. decode and print" logic. The recent `-o hex --json` double-printing bug was a direct consequence — easy to forget one of the `if !args.json` guards. Split the flow into a `decode_response` step that returns a `Decoded` enum (Candid / Text / Bytes) and a single emission step that forks on `--json` exactly once. Semantics are unchanged: `-o` still controls decoding strictness, `--json` still controls envelope vs. human output, and the two remain orthogonal. The write-vs-decode error reconciliation in JSON mode is preserved. Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Linwei Shang <linwei.shang@dfinity.org> Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Proposed addition to #553 — same fix, restructured so the bug class is harder to reintroduce.
Context
In
canister call, two flags control output:-o {auto,candid,text,hex}— how to decode the response.--json— wrap the result in a JSON envelope{response_bytes, response_text?, response_candid?}.They are orthogonal:
-osays what decoding to attempt (and whether failure is fatal),--jsonsays how to emit. Previously, eachCallOutputModearm contained its ownif args.json { stash } else { print }fork, and a trailing block then serialized the envelope. With four arms × two branches, it was easy for one of the guards to fall out of sync — which is what happened with-o hex --json.Change
Split the flow into two steps:
decode_response(&res, mode, method) -> Result<Decoded, _>whereDecoded ∈ {Candid, Text, Bytes}. This is the only place mode-specific logic lives. Error contexts (response (hex): …,response is not valid UTF-8) are preserved.args.jsonexactly once — either build the envelope fromDecodedand serialize, or pretty-print to the terminal.Semantics are unchanged:
-ostill controls decoding strictness.--jsonstill controls envelope vs. human emission.-o hex --json,-o candid --json, etc. all behave as in fix: Don't print response in-o hex --json#553.