[fylorn]

Why

set and insert only ever touched scalars, so the patch protocol could express exactly one thing: replace a value that already exists. Every structural edit was therefore impossible from the UI — creating a key, adding a rule, defining a proxy, assigning a route. None of those is a replacement.

That was less a missing feature than a ceiling: the configuration page could read anything and create nothing.

tw_yaml::append / tw_yaml::remove

Block sequences, operating on the text rather than a re-serialised document, so comments and layout survive — the whole reason this crate exists.

Positions come from walking lines, not from container nodes' byte ranges. Those ranges run on to the next token (the note at the top of the file says so), and slicing with them takes the following entry's opening with it.

Four behaviours worth naming, each with a test:

• A blank line between entries belongs to the following entry. Attached to the preceding one, deleting a middle entry glues its neighbours together.
• Indentation is copied from the entry already there. A four-space file gets four-space entries — it is the user's file.
• A trailing comment on the last entry stays on the last entry.
• Nested sequences work, which is what the routes page needs: /routes/默认/rules.

Empty sequences are refused with a message saying so, rather than writing something that will not parse. clients: [] cannot be appended to yet; validation already requires at least one client, so the case that matters in practice is covered.

The structural guard mirrors the scalar one — re-parse in memory, then count. The scalar path asserts "the value reads back"; this one asserts "the list is exactly one longer". Writing a file that cannot be parsed is what this layer exists to prevent, and it would otherwise surface only at the next load.

PatchOp::Append / PatchOp::Remove

Remove takes a path to the entry, by name — /clients/codex — not an index. That is the rule already written on PatchOp: an index points at something else once the user reorders, and that failure is silent. The index is resolved internally, from a name the user wrote, with no reordering in between.

A new entry can carry nested structure in one write, so creating a key and assigning its routes is a single operation. Two writes would leave a moment where a key exists with no routes — a state the user can see.

Verification

cargo fmt --all -- --check, cargo clippy --workspace --all-targets -- -D warnings, 1088 tests (10 new: 7 on the YAML operations, 3 on the patch path end to end), and scripts/smoke.sh — 46 checks, 0 failures.

🤖 Generated with Claude Code