## Objective
Sometimes we can do a hash lookup twice, which is slow and unidiomatic.
We should use the Entry API instead.
## Solution
Add another `dylint` lint called `map_lookup_then_insert` that catches
those cases.
This works with HashMap, BTreeMap, HashSet, BTreeSet and
entry-compatible ADTs.
## What it catches
See the examples in the `tooling/lints/ui/map_lookup_then_insert.rs`.
It's mostly things of the form
```rust
if let Some(value) = map.get(&key) {
*value
} else {
map.insert(key, 1);
1
}
```
which should be
```rust
*map.entry(key).or_insert(1)
```
The two key expressions 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 by
name),
and immutable local aliases. So looking up `&key` and inserting
`key.clone()`
is caught too. When a conversion had to be peeled, the diagnostic
carries a
note that an entry-API rewrite would perform that copy on hits as well
as
misses.
## What it deliberately does not catch
Forms Clippy already catches.
## Findings
A `--workspace` run finds 31 warnings at 30 unique sites in `zed`:
the 16 the plain key matching finds, plus 15 more that require the
conversion/alias matching (e.g. `tiles_by_key.get(key)` followed by
`tiles_by_key.insert(key.clone(), tile)` in `metal_atlas.rs`).
Will post those fixes in a follow up PR.
## Testing
UI tests cover every `Entry` method positively and negatively, BTreeMap
mirrors, set cases, and the Clippy-deferral boundary. The
key-normalization logic is covered by nine positive cases (cloned keys,
UFCS forms, `to_owned`/`to_string`/`to_vec`/`String::from`, deref
layers, local aliases, sets) and six negative cases (inherent methods
merely named `clone`/`to_owned`, mutated aliases, a clone of a different
key, `to_string` on a non-string key, and side-effecting initializers).
## Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- N/A
Stacked on #60502 and targets it — #60502 must land first (its
orchestrator fix is what lets this `tooling/lints/`-touching PR go green
rather than tripping the `rdeps(lints)` nextest filter). Re-creates the
symlinks from #60504, which was accidentally merged into #60502's branch
and reverted.
Follow-up to #60468, which added a `LICENSE-APACHE` symlink to the
`tooling/lints` crate but not to the `test_fixture` sub-crates. Those
five sub-crates each carry a `Cargo.toml`, so `script/check-licenses`
requires a `LICENSE-GPL`/`LICENSE-APACHE` symlink in each, and
`check_licenses` fails on any PR that changes `Cargo.lock`. This adds
`LICENSE-APACHE` symlinks to the five fixture crates, matching #60468;
`script/check-licenses` passes locally afterward.
Release Notes:
- N/A
Seeing `script/check-license` fail because we forgot to add a license in
#58496
> Error: tooling/lints does not contain a LICENSE-GPL or LICENSE-APACHE
symlink
Release Notes:
- N/A
Adds a dylint library under tooling/lints that flags Zed-specific
anti-patterns:
* shared_string_from_str_literal,
* async_block_without_await,
* entity_update_in_render,
* notify_in_render,
* owned_string_into_shared,
* len_in_loop_condition, and
* blocking_io_on_foreground.
Includes UI tests, a single-lint helper, and workspace.metadata.dylint
registration so cargo dylint --all discovers it. The library pins its
own nightly toolchain (kept out of the main workspace) and tracks dylint
6.
Release Notes:
- N/A
Self-Review Checklist:
- [ ] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [ ] Performance impact has been considered and is acceptable
Closes #ISSUE
Release Notes:
- N/A or Added/Fixed/Improved ...
Miguel Raz Guzmán Macedo