fix(aws): honor explicit --output json/yaml losslessly

[maxmilian]

Summary

• Fixes aws lambda commands: rtk corrupts --output json (returns non-JSON schema skeleton, drops field values) #2139: rtk aws ... --output json returned a lossy schema skeleton (string, int, string[64]) or a one-line table summary instead of valid JSON, dropping field values (ImageUri, CodeSha256, env vars) and breaking downstream jq / json.load.
• Root cause: rtk applied its summarizers (filter_lambda_get) or generic schema compression (filter_json_string) regardless of the user-requested output format.
• Fix: when the user explicitly requests a structured, parseable format (--output json / --output=json / yaml / yaml-stream), run() short-circuits to a new byte-faithful run_passthrough. Lossy/human formats (table, text) and the no-flag default keep the existing compression behavior.

This covers all aws subcommands, not just lambda.

Test plan

• cargo fmt --all clean
• cargo clippy --all-targets — zero warnings
• cargo test --all — 1947 passed
• New unit test test_explicit_lossless_format covers json/yaml/=json positives and table/text/absent negatives

🤖 Generated with Claude Code

[maxmilian]

Automated triage on #2139 (by wshm) independently confirms this: categorized as bug, priority high, 93% confidence, with the recommended fix being to "bypass summarization when an explicit output format flag is present" — which is exactly what this PR does.

This PR narrows that slightly: it only bypasses for parseable formats (json / yaml / yaml-stream) where losslessness is a contract, while keeping the existing compression for the human-readable table / text formats and the no-flag default — so token savings are preserved everywhere they don't break parsing.

[maxmilian]

Note for the PR Testing Checklist: the "token savings ≥60%" item is N/A here. This isn't a new/compressing filter — it's a correctness fix that bypasses compression when the user explicitly requests --output json/yaml. It directly applies design principle Correctness vs Token Savings: a flag that explicitly asks for parseable, lossless output must not be reformatted into a lossy summary/skeleton.

The remaining checklist items are covered:

• Unit tests added (test_explicit_lossless_format, incl. repeated/dangling --output)
• cargo fmt --all --check && cargo clippy --all-targets && cargo test — all green (1947 passed)
• Manual rtk aws ... --output json verified to pass through byte-for-byte

On security: the new run_passthrough forwards the user's args to the aws binary via Command::arg (no shell string interpolation), so it doesn't widen any injection surface versus the existing runners.

[dessite]

I believe I tackled this problem a bit differently a few hours earlier #2135 ;) rtk adds --output json on it's own if no --output defined afair

[maxmilian]

Thanks @dessite — I looked at #2135 and I don't think they collide; they fix different layers and are actually complementary.

#2135 swaps filter_json_string → filter_json_compact in run_generic, so the compressed output keeps real values instead of string/int placeholders. That's a real improvement for the default token-saving path. But by design the output is still rtk's compact form — unquoted keys, depth cap, array summarization (your own "After" shows GlobalSettings: with no quotes) — so it's still not parseable JSON; jq / json.load would still choke on it.

#2140 (this PR) targets the --output json|yaml contract (#2139): when the user explicitly asks for a structured, parseable format, it short-circuits to a byte-faithful passthrough — the real aws output, untouched — so downstream parsing works. The default/no-flag path and table/text keep the existing compression (i.e. they keep your #2135 improvement).

Two notes specific to #2139:

• The repro spans two routes. lambda get-function-configuration falls to _ => run_generic (so fix(aws): preserve values in JSON output for unsupported subcommands #2135 improves it — but to compact, not valid JSON), while lambda get-function has a specialized handler (filter_lambda_get, aws_cmd.rs:120) and never reaches run_generic, so fix(aws): preserve values in JSON output for unsupported subcommands #2135 doesn't touch that one at all. fix(aws): honor explicit --output json/yaml losslessly #2140 covers both because it short-circuits in run() before any handler.
• It also covers yaml/yaml-stream, not just json.

On "rtk adds --output json on its own if none is defined" — agreed, and that auto-added path stays on run_generic (your territory). explicit_lossless_format only inspects the args the user actually passed, so rtk's auto-injected json isn't treated as explicit and the two don't overlap.

So I think both can land: #2135 makes the default compressed output value-preserving, #2140 honors an explicit format request losslessly. Happy to defer to maintainers on sequencing though.

[maxmilian]

Rebased onto latest develop and resolved the conflict with #2135 (now merged as ad2bfd3).

The two changes sit at different layers and compose cleanly:

• fix(aws): preserve values in JSON output for unsupported subcommands #2135 makes run_generic use filter_json_compact so unsupported subcommands keep their values — but it still applies depth/string-length/array-size truncation, and the compact form isn't byte-faithful JSON.
• This PR intercepts at the top of run(): when the user explicitly passes --output json/yaml, it routes to run_passthrough and emits the aws output byte-for-byte, so … --output json | jq / json.load keep working. No overlap — explicit-lossless is handled before run_generic is ever reached, while fix(aws): preserve values in JSON output for unsupported subcommands #2135 still governs the auto-injected-json path.

Conflict was a one-line doc comment on run_generic; kept #2135's wording ("compact (values preserved)") and layered the explicit-lossless functions ahead of it.

Validation on the rebased branch: cargo fmt --check clean, cargo clippy --all-targets clean, cargo test 2073 passed / 0 failed (incl. #2135's test_aws_unsupported_subcommand_json_preserves_values and this PR's test_explicit_lossless_format).