feat(linter): eslint-plugin-jest: prefer-spy-on (#2666)

Rule Detail:
[link](https://github.com/jest-community/eslint-plugin-jest/blob/main/src/rules/prefer-spy-on.ts)

crates/oxc_linter/src/rules.rs

@@ -153,6 +153,7 @@ mod jest {
     pub mod no_test_return_statement;
     pub mod prefer_called_with;
     pub mod prefer_equality_matcher;
+    pub mod prefer_spy_on;
     pub mod prefer_strict_equal;
     pub mod prefer_to_have_length;
     pub mod prefer_todo;
@@ -456,6 +457,7 @@ oxc_macros::declare_all_lint_rules! {
     jest::no_test_return_statement,
     jest::prefer_called_with,
     jest::prefer_equality_matcher,
+    jest::prefer_spy_on,
     jest::prefer_strict_equal,
     jest::prefer_to_have_length,
     jest::prefer_todo,

crates/oxc_linter/src/rules/jest/prefer_spy_on.rs

@@ -0,0 +1,301 @@
+use oxc_ast::{
+    ast::{
+        Argument, AssignmentExpression, AssignmentTarget, CallExpression, Expression,
+        MemberExpression, SimpleAssignmentTarget,
+    },
+    AstKind,
+};
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::Error,
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_semantic::AstNode;
+use oxc_span::Span;
+
+use crate::{
+    context::LintContext,
+    fixer::Fix,
+    rule::Rule,
+    utils::{get_node_name, parse_general_jest_fn_call, PossibleJestNode},
+};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.")]
+#[diagnostic(severity(warning), help("Use jest.spyOn() instead"))]
+struct UseJestSpyOn(#[label] pub Span);
+
+#[derive(Debug, Default, Clone)]
+pub struct PreferSpyOn;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// When mocking a function by overwriting a property you have to manually restore
+    /// the original implementation when cleaning up. When using `jest.spyOn()` Jest
+    /// keeps track of changes, and they can be restored with `jest.restoreAllMocks()`,
+    /// `mockFn.mockRestore()` or by setting `restoreMocks` to `true` in the Jest
+    /// config.
+    ///
+    /// Note: The mock created by `jest.spyOn()` still behaves the same as the original
+    /// function. The original function can be overwritten with
+    /// `mockFn.mockImplementation()` or by some of the
+    /// [other mock functions](https://jestjs.io/docs/en/mock-function-api).
+    ///
+    /// ### Example
+    ///
+    /// ```javascript
+    /// // invalid
+    /// Date.now = jest.fn();
+    /// Date.now = jest.fn(() => 10);
+    ///
+    /// // valid
+    /// jest.spyOn(Date, 'now');
+    /// jest.spyOn(Date, 'now').mockImplementation(() => 10);
+    /// ```
+    PreferSpyOn,
+    style,
+);
+
+impl Rule for PreferSpyOn {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        let AstKind::AssignmentExpression(assign_expr) = node.kind() else {
+            return;
+        };
+
+        let left = &assign_expr.left;
+        let right = &assign_expr.right;
+
+        let AssignmentTarget::SimpleAssignmentTarget(
+            SimpleAssignmentTarget::MemberAssignmentTarget(left_assign),
+        ) = left
+        else {
+            return;
+        };
+
+        match right {
+            Expression::CallExpression(call_expr) => {
+                Self::check_and_fix(assign_expr, call_expr, left_assign, node, ctx);
+            }
+            Expression::MemberExpression(mem_expr) => {
+                let Expression::CallExpression(call_expr) = mem_expr.object() else {
+                    return;
+                };
+                Self::check_and_fix(assign_expr, call_expr, left_assign, node, ctx);
+            }
+            _ => (),
+        }
+    }
+}
+
+impl PreferSpyOn {
+    fn check_and_fix<'a>(
+        assign_expr: &AssignmentExpression,
+        call_expr: &'a CallExpression<'a>,
+        left_assign: &MemberExpression,
+        node: &AstNode<'a>,
+        ctx: &LintContext<'a>,
+    ) {
+        let Some(jest_fn_call) =
+            parse_general_jest_fn_call(call_expr, &PossibleJestNode { node, original: None }, ctx)
+        else {
+            return;
+        };
+        let Some(first_fn_member) = jest_fn_call.members.first() else {
+            return;
+        };
+
+        if first_fn_member.name().unwrap() != "fn" {
+            return;
+        }
+
+        ctx.diagnostic_with_fix(
+            UseJestSpyOn(Span::new(call_expr.span.start, first_fn_member.span.end)),
+            || {
+                let (end, has_mock_implementation) = if jest_fn_call.members.len() > 1 {
+                    let second = &jest_fn_call.members[1];
+                    let has_mock_implementation = jest_fn_call
+                        .members
+                        .iter()
+                        .filter(|member| member.is_name_equal("mockImplementation"))
+                        .count()
+                        > 0;
+
+                    (second.span.start - 1, has_mock_implementation)
+                } else {
+                    (
+                        first_fn_member.span.end + (call_expr.span.end - first_fn_member.span.end),
+                        false,
+                    )
+                };
+                let content =
+                    Self::build_code(call_expr, left_assign, has_mock_implementation, ctx);
+                Fix::new(content, Span::new(assign_expr.span.start, end))
+            },
+        );
+    }
+
+    fn build_code<'a>(
+        call_expr: &'a CallExpression<'a>,
+        left_assign: &MemberExpression,
+        has_mock_implementation: bool,
+        ctx: &LintContext,
+    ) -> String {
+        let mut formatter = ctx.codegen();
+        formatter.print_str(b"jest.spyOn(");
+
+        match left_assign {
+            MemberExpression::ComputedMemberExpression(cmp_mem_expr) => {
+                formatter.print_expression(&cmp_mem_expr.object);
+                formatter.print(b',');
+                formatter.print_hard_space();
+                formatter.print_expression(&cmp_mem_expr.expression);
+            }
+            MemberExpression::StaticMemberExpression(static_mem_expr) => {
+                let name = &static_mem_expr.property.name;
+                formatter.print_expression(&static_mem_expr.object);
+                formatter.print(b',');
+                formatter.print_hard_space();
+                formatter.print_str(format!("\'{name}\'").as_bytes());
+            }
+            MemberExpression::PrivateFieldExpression(_) => (),
+        }
+
+        formatter.print(b')');
+
+        if has_mock_implementation {
+            return formatter.into_source_text();
+        }
+
+        formatter.print_str(b".mockImplementation(");
+
+        if let Some(Argument::Expression(expr)) = Self::get_jest_fn_call(call_expr) {
+            formatter.print_expression(expr);
+        }
+
+        formatter.print(b')');
+        formatter.into_source_text()
+    }
+
+    fn get_jest_fn_call<'a>(call_expr: &'a CallExpression<'a>) -> Option<&'a Argument<'a>> {
+        let is_jest_fn = get_node_name(&call_expr.callee) == "jest.fn";
+
+        if is_jest_fn {
+            return call_expr.arguments.first();
+        }
+
+        match &call_expr.callee {
+            Expression::MemberExpression(mem_expr) => {
+                if let Some(call_expr) = Self::find_mem_expr(mem_expr) {
+                    return Self::get_jest_fn_call(call_expr);
+                }
+                None
+            }
+            Expression::CallExpression(call_expr) => Self::get_jest_fn_call(call_expr),
+            _ => None,
+        }
+    }
+
+    fn find_mem_expr<'a>(mem_expr: &'a MemberExpression<'a>) -> Option<&'a CallExpression<'a>> {
+        match mem_expr.object() {
+            Expression::CallExpression(call_expr) => Some(call_expr),
+            Expression::MemberExpression(mem_expr) => Self::find_mem_expr(mem_expr),
+            _ => None,
+        }
+    }
+}
+
+#[test]
+fn tests() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        ("Date.now = () => 10", None),
+        ("window.fetch = jest.fn", None),
+        ("Date.now = fn()", None),
+        ("obj.mock = jest.something()", None),
+        ("const mock = jest.fn()", None),
+        ("mock = jest.fn()", None),
+        ("const mockObj = { mock: jest.fn() }", None),
+        ("mockObj = { mock: jest.fn() }", None),
+        ("window[`${name}`] = jest[`fn${expression}`]()", None),
+    ];
+
+    let fail = vec![
+        ("obj.a = jest.fn(); const test = 10;", None),
+        ("Date['now'] = jest['fn']()", None),
+        ("window[`${name}`] = jest[`fn`]()", None),
+        ("obj['prop' + 1] = jest['fn']()", None),
+        ("obj.one.two = jest.fn(); const test = 10;", None),
+        ("obj.a = jest.fn(() => 10,)", None),
+        (
+            "obj.a.b = jest.fn(() => ({})).mockReturnValue('default').mockReturnValueOnce('first call'); test();",
+            None,
+        ),
+        ("window.fetch = jest.fn(() => ({})).one.two().three().four", None),
+        ("foo[bar] = jest.fn().mockReturnValue(undefined)", None),
+        (
+            "
+                foo.bar = jest.fn().mockImplementation(baz => baz)
+                foo.bar = jest.fn(a => b).mockImplementation(baz => baz)
+            ",
+            None,
+        ),
+    ];
+
+    let fix = vec![
+        (
+            "obj.a = jest.fn(); const test = 10;",
+            "jest.spyOn(obj, 'a').mockImplementation(); const test = 10;",
+            None,
+        ),
+        ("Date['now'] = jest['fn']()", "jest.spyOn(Date, 'now').mockImplementation()", None),
+        (
+            "window[`${name}`] = jest[`fn`]()",
+            "jest.spyOn(window, `${name}`).mockImplementation()",
+            None,
+        ),
+        (
+            "obj['prop' + 1] = jest['fn']()",
+            "jest.spyOn(obj, 'prop' + 1).mockImplementation()",
+            None,
+        ),
+        (
+            "obj.one.two = jest.fn(); const test = 10;",
+            "jest.spyOn(obj.one, 'two').mockImplementation(); const test = 10;",
+            None,
+        ),
+        ("obj.a = jest.fn(() => 10,)", "jest.spyOn(obj, 'a').mockImplementation(() => 10)", None),
+        (
+            "obj.a.b = jest.fn(() => ({})).mockReturnValue('default').mockReturnValueOnce('first call'); test();",
+            "jest.spyOn(obj.a, 'b').mockImplementation(() => ({})).mockReturnValue('default').mockReturnValueOnce('first call'); test();",
+            None,
+        ),
+        (
+            "window.fetch = jest.fn(() => ({})).one.two().three().four",
+            "jest.spyOn(window, 'fetch').mockImplementation(() => ({})).one.two().three().four",
+            None,
+        ),
+        (
+            "foo[bar] = jest.fn().mockReturnValue(undefined)",
+            "jest.spyOn(foo, bar).mockImplementation().mockReturnValue(undefined)",
+            None,
+        ),
+        (
+            "
+                foo.bar = jest.fn().mockImplementation(baz => baz)
+                foo.bar = jest.fn(a => b).mockImplementation(baz => baz)
+            ",
+            "
+                jest.spyOn(foo, 'bar').mockImplementation(baz => baz)
+                jest.spyOn(foo, 'bar').mockImplementation(baz => baz)
+            ",
+            None,
+        ),
+    ];
+
+    Tester::new(PreferSpyOn::NAME, pass, fail)
+        .with_jest_plugin(true)
+        .expect_fix(fix)
+        .test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/prefer_spy_on.snap

@@ -0,0 +1,85 @@
+---
+source: crates/oxc_linter/src/tester.rs
+assertion_line: 151
+expression: prefer_spy_on
+---
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:9]
+ 1 │ obj.a = jest.fn(); const test = 10;
+   ·         ───────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:15]
+ 1 │ Date['now'] = jest['fn']()
+   ·               ─────────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:21]
+ 1 │ window[`${name}`] = jest[`fn`]()
+   ·                     ─────────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:19]
+ 1 │ obj['prop' + 1] = jest['fn']()
+   ·                   ─────────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:15]
+ 1 │ obj.one.two = jest.fn(); const test = 10;
+   ·               ───────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:9]
+ 1 │ obj.a = jest.fn(() => 10,)
+   ·         ───────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:11]
+ 1 │ obj.a.b = jest.fn(() => ({})).mockReturnValue('default').mockReturnValueOnce('first call'); test();
+   ·           ───────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:16]
+ 1 │ window.fetch = jest.fn(() => ({})).one.two().three().four
+   ·                ───────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:1:12]
+ 1 │ foo[bar] = jest.fn().mockReturnValue(undefined)
+   ·            ───────
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:2:27]
+ 1 │ 
+ 2 │                 foo.bar = jest.fn().mockImplementation(baz => baz)
+   ·                           ───────
+ 3 │                 foo.bar = jest.fn(a => b).mockImplementation(baz => baz)
+   ╰────
+  help: Use jest.spyOn() instead
+
+  ⚠ eslint-plugin-jest(prefer-spy-on): Suggest using `jest.spyOn()`.
+   ╭─[prefer_spy_on.tsx:3:27]
+ 2 │                 foo.bar = jest.fn().mockImplementation(baz => baz)
+ 3 │                 foo.bar = jest.fn(a => b).mockImplementation(baz => baz)
+   ·                           ───────
+ 4 │             
+   ╰────
+  help: Use jest.spyOn() instead