feat(linter/vitest): implement prefer-each (#5203)

Related to #4656

---------

Co-authored-by: Don Isaac <donald.isaac@gmail.com>

crates/oxc_linter/src/rules.rs

@@ -458,6 +458,7 @@ mod promise {
 mod vitest {
     pub mod no_conditional_tests;
     pub mod no_import_node_test;
+    pub mod prefer_each;
     pub mod prefer_to_be_falsy;
     pub mod prefer_to_be_truthy;
     pub mod require_local_test_context_for_concurrent_snapshots;
@@ -874,6 +875,7 @@ oxc_macros::declare_all_lint_rules! {
     promise::no_return_in_finally,
     promise::prefer_await_to_then,
     vitest::no_import_node_test,
+    vitest::prefer_each,
     vitest::prefer_to_be_falsy,
     vitest::prefer_to_be_truthy,
     vitest::no_conditional_tests,

crates/oxc_linter/src/rules/vitest/prefer_each.rs

@@ -0,0 +1,283 @@
+use std::collections::HashSet;
+
+use oxc_ast::AstKind;
+use oxc_diagnostics::OxcDiagnostic;
+use oxc_macros::declare_oxc_lint;
+use oxc_semantic::{AstNode, AstNodeId};
+use oxc_span::{GetSpan, Span};
+
+use crate::{
+    context::LintContext,
+    rule::Rule,
+    utils::{parse_jest_fn_call, JestFnKind, JestGeneralFnKind, PossibleJestNode},
+};
+
+fn use_prefer_each(span: Span, fn_name: &str) -> OxcDiagnostic {
+    OxcDiagnostic::warn("Enforce using `each` rather than manual loops")
+        .with_help(format!("Prefer using `{fn_name}.each` rather than a manual loop."))
+        .with_label(span)
+}
+
+#[inline]
+fn is_in_test(ctx: &LintContext<'_>, id: AstNodeId) -> bool {
+    ctx.nodes().iter_parents(id).any(|node| {
+        let AstKind::CallExpression(ancestor_call_expr) = node.kind() else { return false };
+        let Some(ancestor_member_expr) = ancestor_call_expr.callee.as_member_expression() else {
+            return false;
+        };
+        let Some(id) = ancestor_member_expr.object().get_identifier_reference() else {
+            return false;
+        };
+
+        matches!(JestFnKind::from(id.name.as_str()), JestFnKind::General(JestGeneralFnKind::Test))
+    })
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct PreferEach;
+
+declare_oxc_lint!(
+    /// ### What it does
+    /// This rule enforces using `each` rather than manual loops.
+    ///
+    /// ### Examples
+    ///
+    /// Examples of **incorrect** code for this rule:
+    /// ```js
+    /// for (const item of items) {
+    /// 	describe(item, () => {
+    /// 		expect(item).toBe('foo')
+    /// 	})
+    /// }
+    /// ```
+    ///
+    /// Examples of **correct** code for this rule:
+    /// ```js
+    /// describe.each(items)('item', (item) => {
+    /// 	expect(item).toBe('foo')
+    /// })
+    /// ```
+    PreferEach,
+    style,
+);
+
+impl Rule for PreferEach {
+    fn run_once(&self, ctx: &LintContext<'_>) {
+        let mut skip = HashSet::<AstNodeId>::new();
+        ctx.nodes().iter().for_each(|node| {
+            Self::run(node, ctx, &mut skip);
+        });
+    }
+}
+
+impl PreferEach {
+    fn run<'a>(node: &AstNode<'a>, ctx: &LintContext<'a>, skip: &mut HashSet<AstNodeId>) {
+        let kind = node.kind();
+
+        let AstKind::CallExpression(call_expr) = kind else { return };
+
+        let Some(vitest_fn_call) =
+            parse_jest_fn_call(call_expr, &PossibleJestNode { node, original: None }, ctx)
+        else {
+            return;
+        };
+
+        if !matches!(
+            vitest_fn_call.kind(),
+            JestFnKind::General(
+                JestGeneralFnKind::Describe | JestGeneralFnKind::Hook | JestGeneralFnKind::Test
+            )
+        ) {
+            return;
+        }
+
+        for parent_node in ctx.nodes().iter_parents(node.id()).skip(1) {
+            match parent_node.kind() {
+                AstKind::CallExpression(_) => {
+                    return;
+                }
+                AstKind::ForStatement(_)
+                | AstKind::ForInStatement(_)
+                | AstKind::ForOfStatement(_) => {
+                    if skip.contains(&parent_node.id()) || is_in_test(ctx, parent_node.id()) {
+                        return;
+                    }
+
+                    let fn_name = if matches!(
+                        vitest_fn_call.kind(),
+                        JestFnKind::General(JestGeneralFnKind::Test)
+                    ) {
+                        "it"
+                    } else {
+                        "describe"
+                    };
+
+                    let span = match parent_node.kind() {
+                        AstKind::ForStatement(statement) => {
+                            Span::new(statement.span.start, statement.body.span().start)
+                        }
+                        AstKind::ForInStatement(statement) => {
+                            Span::new(statement.span.start, statement.body.span().start)
+                        }
+                        AstKind::ForOfStatement(statement) => {
+                            Span::new(statement.span.start, statement.body.span().start)
+                        }
+                        _ => unreachable!(),
+                    };
+
+                    skip.insert(parent_node.id());
+                    ctx.diagnostic(use_prefer_each(span, fn_name));
+
+                    break;
+                }
+                _ => {}
+            }
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        r#"it("is true", () => { expect(true).toBe(false) });"#,
+        r#"it.each(getNumbers())("only returns numbers that are greater than seven", number => {
+			     expect(number).toBeGreaterThan(7);
+			      });"#,
+        r#"it("returns numbers that are greater than five", function () {
+			     for (const number of getNumbers()) {
+			       expect(number).toBeGreaterThan(5);
+			     }
+			      });"#,
+        r#"it("returns things that are less than ten", function () {
+			     for (const thing in things) {
+			       expect(thing).toBeLessThan(10);
+			     }
+			      });"#,
+        r#"it("only returns numbers that are greater than seven", function () {
+			     const numbers = getNumbers();
+			   
+			     for (let i = 0; i < numbers.length; i++) {
+			       expect(numbers[i]).toBeGreaterThan(7);
+			     }
+			      });"#,
+    ];
+
+    let fail = vec![
+        "  for (const [input, expected] of data) {
+			      it(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }",
+        " for (const [input, expected] of data) {
+			      describe(`when the input is ${input}`, () => {
+			        it(`results in ${expected}`, () => {
+			       expect(fn(input)).toBe(expected)
+			        });
+			      });
+			       }",
+        "for (const [input, expected] of data) {
+			      describe(`when the input is ${input}`, () => {
+			        it(`results in ${expected}`, () => {
+			       expect(fn(input)).toBe(expected)
+			        });
+			      });
+			       }
+			     
+			       for (const [input, expected] of data) {
+			      it.skip(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }",
+        "for (const [input, expected] of data) {
+			      it.skip(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }",
+        "it('is true', () => {
+			      expect(true).toBe(false);
+			       });
+			     
+			       for (const [input, expected] of data) {
+			      it.skip(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }",
+        " for (const [input, expected] of data) {
+			      it.skip(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }
+			     
+			       it('is true', () => {
+			      expect(true).toBe(false);
+			       });",
+        " it('is true', () => {
+			      expect(true).toBe(false);
+			       });
+			     
+			       for (const [input, expected] of data) {
+			      it.skip(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }
+			     
+			       it('is true', () => {
+			      expect(true).toBe(false);
+			       });",
+        "for (const [input, expected] of data) {
+			      it(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			     
+			      it(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }",
+        "for (const [input, expected] of data) {
+			      it(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }
+			     
+			       for (const [input, expected] of data) {
+			      it(`results in ${expected}`, () => {
+			        expect(fn(input)).toBe(expected)
+			      });
+			       }",
+        "for (const [input, expected] of data) {
+			      beforeEach(() => setupSomething(input));
+			     
+			      test(`results in ${expected}`, () => {
+			        expect(doSomething()).toBe(expected)
+			      });
+			       }",
+        r#"
+			       for (const [input, expected] of data) {
+			      it("only returns numbers that are greater than seven", function () {
+			        const numbers = getNumbers(input);
+			    
+			        for (let i = 0; i < numbers.length; i++) {
+			       expect(numbers[i]).toBeGreaterThan(7);
+			        }
+			      });
+			       }
+			     "#,
+        r#"
+			       for (const [input, expected] of data) {
+			      beforeEach(() => setupSomething(input));
+			     
+			      it("only returns numbers that are greater than seven", function () {
+			        const numbers = getNumbers();
+			    
+			        for (let i = 0; i < numbers.length; i++) {
+			       expect(numbers[i]).toBeGreaterThan(7);
+			        }
+			      });
+			       }
+			     "#,
+    ];
+
+    Tester::new(PreferEach::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/prefer_each.snap

@@ -0,0 +1,120 @@
+---
+source: crates/oxc_linter/src/tester.rs
+---
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:3]
+ 1 │   for (const [input, expected] of data) {
+   ·   ──────────────────────────────────────
+ 2 │                   it(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:2]
+ 1 │  for (const [input, expected] of data) {
+   ·  ──────────────────────────────────────
+ 2 │                   describe(`when the input is ${input}`, () => {
+   ╰────
+  help: Prefer using `describe.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:1]
+ 1 │ for (const [input, expected] of data) {
+   · ──────────────────────────────────────
+ 2 │                   describe(`when the input is ${input}`, () => {
+   ╰────
+  help: Prefer using `describe.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+    ╭─[prefer_each.tsx:9:11]
+  8 │                  
+  9 │                    for (const [input, expected] of data) {
+    ·                    ──────────────────────────────────────
+ 10 │                   it.skip(`results in ${expected}`, () => {
+    ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:1]
+ 1 │ for (const [input, expected] of data) {
+   · ──────────────────────────────────────
+ 2 │                   it.skip(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:5:11]
+ 4 │                  
+ 5 │                    for (const [input, expected] of data) {
+   ·                    ──────────────────────────────────────
+ 6 │                   it.skip(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:2]
+ 1 │  for (const [input, expected] of data) {
+   ·  ──────────────────────────────────────
+ 2 │                   it.skip(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:5:11]
+ 4 │                  
+ 5 │                    for (const [input, expected] of data) {
+   ·                    ──────────────────────────────────────
+ 6 │                   it.skip(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:1]
+ 1 │ for (const [input, expected] of data) {
+   · ──────────────────────────────────────
+ 2 │                   it(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:1]
+ 1 │ for (const [input, expected] of data) {
+   · ──────────────────────────────────────
+ 2 │                   it(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:7:11]
+ 6 │                  
+ 7 │                    for (const [input, expected] of data) {
+   ·                    ──────────────────────────────────────
+ 8 │                   it(`results in ${expected}`, () => {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:1:1]
+ 1 │ for (const [input, expected] of data) {
+   · ──────────────────────────────────────
+ 2 │                   beforeEach(() => setupSomething(input));
+   ╰────
+  help: Prefer using `describe.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:2:11]
+ 1 │ 
+ 2 │                    for (const [input, expected] of data) {
+   ·                    ──────────────────────────────────────
+ 3 │                   it("only returns numbers that are greater than seven", function () {
+   ╰────
+  help: Prefer using `it.each` rather than a manual loop.
+
+  ⚠ eslint-plugin-vitest(prefer-each): Enforce using `each` rather than manual loops
+   ╭─[prefer_each.tsx:2:11]
+ 1 │ 
+ 2 │                    for (const [input, expected] of data) {
+   ·                    ──────────────────────────────────────
+ 3 │                   beforeEach(() => setupSomething(input));
+   ╰────
+  help: Prefer using `describe.each` rather than a manual loop.