zed/tooling/lints

lints

A dylint library that flags various bad patterns in our codebase.

Install dylint, a pinned nightly toolchain and the necessary tools with

cargo install cargo-dylint dylint-link
cd tooling/lints
rustup toolchain install

The channel and its components (rustc-dev, rust-src, llvm-tools-preview) are declared in tooling/lints/rust-toolchain.toml, so rustup toolchain install picks them up automatically when run from that directory.

Demo

./single-lint blocking_io_on_foreground

Current lints

• shared_string_from_str_literal — SharedString::new/from etc where SharedString::from_static should be used instead.
• async_block_without_await — async { … } blocks whose body contains no .await expression.
• entity_update_in_render — Entity::update/WeakEntity::update mutating an entity inside Render::render.
• map_lookup_then_insert — map value lookups that branch into an insertion for the same key, on any map with an entry method (HashMap, BTreeMap, FxHashMap, hashbrown, indexmap, ...), and the same pattern on HashSet/BTreeSet (where a bare insert already searches only once). Keys are matched up to borrows/derefs, value-preserving conversions (clone, to_owned, to_string on string types, to_vec on slices, String::from on &str — each resolved by definition, not name), and immutable local aliases, so looking up &key and inserting key.clone() is caught.
• notify_in_render — Context::notify() called inside Render::render.
• owned_string_into_shared — String::from(<lit>).into() / <lit>.to_string().into() / <lit>.to_owned().into() whose target is SharedString, Arc<str>, Rc<str>, or Cow<'_, str>.
• blocking_io_on_foreground - Catch blocking IO calls that are called on the main thread (but not on closures or background threads)

How to run

Ideally you run this as part of the clippy script in the zed/scripts directory since this will also run our other linters.

Prerequisites

Install both tools (version 6 or later):

cargo install cargo-dylint dylint-link

• cargo-dylint is the cargo subcommand that builds and runs the lints; dylint-link is the linker used to build the lint library.

The workspace registers this library under [workspace.metadata.dylint] in the root Cargo.toml, so Dylint discovers it automatically — you do not pass a --path. The first run builds the library against its pinned nightly (see rust-toolchain.toml) and is slow; later runs are cached.

Run all lints against the whole repo

cargo dylint --all -- --workspace

Run all lints against a single crate

cargo dylint --all -- -p project_panel

Run a single lint

The library loads every lint at once. To run just one, use the single-lint helper, which silences the rest and force-enables the one you name:

tooling/lints/single-lint blocking_io_on_foreground -p project_panel

The first argument is the lint name (one of the snake_case identifiers under Current lints); everything after it is passed to cargo check and defaults to --workspace. Under the hood the script runs:

DYLINT_RUSTFLAGS="-A warnings --force-warn <lint>" cargo dylint --all -- <args>

It also handles two non-obvious gotchas:

• --force-warn is required: after -A warnings silences the group, a plain -W <lint> does not reliably re-enable a driver-registered lint.
• DYLINT_RUSTFLAGS is not part of Cargo's fingerprint, so the script cleans the targeted package(s) first; otherwise Cargo replays a stale cache and the filter appears to do nothing.