oxc/crates/oxc_semantic/tests/integration/scopes.rs
DonIsaac b952942993 feat(linter): add eslint/no-unused-vars ( attempt 3.2) (#4445)
> Re-creation of #4427 due to rebasing issues. Original attempt: #642
-----

Third time's the charm?

Each time I attempt this rule, I find a bunch of bugs in `Semantic`, and I expect this attempt to be no different. Expect sidecar issues+PRs stemming from this PR here.

## Not Supported
These are cases supported in the original eslint rule, but that I'm intentionally deciding not to support
- export comments in scripts
  ```js
  /* exported a */ var a;
  ```
- global comments
  ```js
  /* global a */ var a;
   ```

## Behavior Changes
These are intentional deviations from the original rule's behavior:
- logical re-assignments are not considered usages
  ```js
  // passes in eslint/no-unused-vars, fails in this implementation
  let a = 0; a ||= 1;
  let b = 0; b &&= 2;
  let c = undefined; c ??= []
  ```

## Known Limitations
- Lint rules do not have babel or tsconfig information, meaning we can't determine if `React` imports are being used or not. The relevant tsconfig settings here are `jsx`, `jsxPragma`, and `jsxFragmentName`. To accommodate this, all imports to symbols named `React` or `h` are ignored in JSX files.
- References to symbols used in JSDoc `{@link}` tags are not created, so symbols that are only used in doc comments will be reported as unused. See: #4443
- `.vue` files are skipped completely, since variables can be used in templates in ways we cannot detect
  > note: `.d.ts` files are skipped as well.

## Todo
- [x] Skip unused TS enum members on used enums
- [x] Skip unused parameters followed by used variables in object/array spreads
- [x] Re-assignments to array/object spreads do not respect `destructuredArrayIgnorePattern` (related to: https://github.com/oxc-project/oxc/issues/4435)
- [x] #4493
- [x] References inside a nested scope are not considered usages (#4447)
- [x] Port over typescript-eslint test cases _(wip, they've been copied and I'm slowly enabling them)_
- [x] Handle constructor properties
  ```ts
  class Foo {
    constructor(public a) {} // `a` should be allowed
  }
  ```
- [x] Read references in sequence expressions (that are not in the last position) should not count as a usage
  ```js
  let a = 0; let b = (a++, 0); console.log(b)
  ```
  > Honestly, is anyone even writing code like this?
- [x] function overload signatures should not be reported
- [x] Named functions returned from other functions get incorrectly reported as unused (found by @camc314)
  ```js
  function foo() {
    return function bar() { }
  }
  Foo()()
  ```
- [x] false positive for TS modules within ambient modules
  ```ts
  declare global {
    // incorrectly marked as unused
    namespace jest { }
  }
  ```

## Blockers
- https://github.com/oxc-project/oxc/issues/4436
- https://github.com/oxc-project/oxc/issues/4437
- #4446
- #4447
- #4494
- #4495

## Non-Blocking Issues
- #4443
- #4475 (prevents checks on exported symbols from namespaces)
2024-07-31 03:22:16 +00:00

199 lines
4.9 KiB
Rust

use oxc_ast::AstKind;
use oxc_semantic::{ScopeFlags, SymbolFlags};
use crate::util::{Expect, SemanticTester};
#[test]
fn test_top_level_strict() {
// Module with top-level "use strict"
SemanticTester::js(
r#"
"use strict";
function foo() {
return 1
}
"#,
)
.has_root_symbol("foo")
.is_in_scope(ScopeFlags::Top | ScopeFlags::StrictMode)
// .expect(expect_strict)
.test();
// Module without top-level "use strict"
SemanticTester::js(
r"
function foo() {
return 1
}
",
)
.has_root_symbol("foo")
.is_in_scope(ScopeFlags::Top | ScopeFlags::StrictMode)
.test();
// Script with top-level "use strict"
SemanticTester::js(
r#"
"use strict";
function foo() {
return 1
}
"#,
)
.with_module(false)
.has_root_symbol("foo")
.is_in_scope(ScopeFlags::Top | ScopeFlags::StrictMode)
.test();
// Script without top-level "use strict"
SemanticTester::js(
r"
function foo() {
return 1
}
",
)
.with_module(false)
.has_root_symbol("foo")
.is_in_scope(ScopeFlags::Top)
.is_not_in_scope(ScopeFlags::StrictMode)
.test();
}
#[test]
fn test_function_level_strict() {
let tester = SemanticTester::js(
r#"
function foo() {
"use strict";
let x = 1;
return x
}
"#,
)
.with_module(false);
tester.has_some_symbol("x")
.is_in_scope(ScopeFlags::StrictMode | ScopeFlags::Function)
.expect(|(semantic, symbol_id)| -> Result<(), &'static str> {
let scope_id = semantic.symbol_scope(symbol_id);
let Some(parent_scope_id) = semantic.scopes().get_parent_id(scope_id) else {
return Err("Expected x's scope to have a parent")
};
let parent_flags = semantic.scopes().get_flags(parent_scope_id);
if parent_flags.contains(ScopeFlags::Top) {
Ok(())
} else {
Err("Expected x to be in a top-level function declaration, but its parent scope has flags {parent_flags:?}")
}
})
.test();
tester.has_some_symbol("foo").is_not_in_scope(ScopeFlags::StrictMode).test();
}
#[test]
fn test_switch_case() {
SemanticTester::js(
"
const foo = 1;
switch (foo) {
case 1:
const foo = 2;
}
",
)
.has_root_symbol("foo")
.has_number_of_references(1)
.test();
}
#[test]
fn test_function_parameters() {
let tester = SemanticTester::js(
"
const foo = 2;
const c = 0;
function func(a = foo, b = c, c = 0) {
const foo = 0;
}
",
);
tester.has_root_symbol("foo").has_number_of_references(1).test();
// b = c should reference the third parameter, so root symbol `c`` should have 0 reference
tester.has_root_symbol("c").has_number_of_references(0).test();
}
#[test]
fn test_catch_clause_parameters() {
SemanticTester::js(
"
const a = 0;
try {
} catch ({ [a]: b }) {
const a = 1;
}
",
)
.has_root_symbol("a")
.has_number_of_references(1)
.test();
}
#[test]
fn test_enums() {
let test = SemanticTester::ts(
"
enum A {
X,
Y,
Z
}",
);
test.has_root_symbol("A").contains_flags(SymbolFlags::RegularEnum).test();
test.has_some_symbol("X").contains_flags(SymbolFlags::EnumMember).test();
let semantic = test.build();
let program = semantic
.nodes()
.iter()
.find(|node| matches!(node.kind(), AstKind::Program(_)))
.expect("No program node found");
assert_eq!(program.scope_id(), semantic.scopes().root_scope_id());
let (enum_node, enum_decl) = semantic
.nodes()
.iter()
.find_map(|node| {
if let AstKind::TSEnumDeclaration(e) = node.kind() {
Some((node, e))
} else {
None
}
})
.expect("Expected TS test case to have an enum declaration for A.");
assert_eq!(
enum_node.scope_id(),
program.scope_id(),
"Expected `enum A` to be created in the top-level scope."
);
let enum_decl_scope_id = enum_decl.scope_id.get().expect("Enum declaration has no scope id");
assert_ne!(enum_node.scope_id(), enum_decl_scope_id, "Enum declaration nodes should contain the scope ID they create, not the scope ID they're created in.");
assert_eq!(enum_decl.members.len(), 3);
}
#[test]
fn var_hoisting() {
SemanticTester::js(
"
try {} catch (e) {
var e = 0;
}
",
)
.has_root_symbol("e")
// `e` was hoisted to the top scope so the symbol's scope is also the top scope
.is_in_scope(ScopeFlags::Top)
.test();
}