feat(linter): add typescript-eslint/no-confusing-non-null-assertion (#…

…4224)

Added logic for
https://typescript-eslint.io/rules/no-confusing-non-null-assertion

Left comments for when Suggest feature is added

---------

Co-authored-by: Don Isaac <[email protected]>

crates/oxc_linter/src/rules.rs

@@ -134,6 +134,7 @@ mod typescript {
     pub mod consistent_type_definitions;
     pub mod consistent_type_imports;
     pub mod explicit_function_return_type;
+    pub mod no_confusing_non_null_assertion;
     pub mod no_duplicate_enum_values;
     pub mod no_dynamic_delete;
     pub mod no_empty_interface;
@@ -561,6 +562,7 @@ oxc_macros::declare_all_lint_rules! {
     typescript::explicit_function_return_type,
     typescript::no_non_null_assertion,
     typescript::no_non_null_asserted_nullish_coalescing,
+    typescript::no_confusing_non_null_assertion,
     typescript::no_dynamic_delete,
     jest::consistent_test_it,
     jest::expect_expect,

crates/oxc_linter/src/rules/typescript/no_confusing_non_null_assertion.rs

@@ -0,0 +1,118 @@
+use oxc_ast::{
+    ast::{Expression, SimpleAssignmentTarget},
+    AstKind,
+};
+use oxc_diagnostics::OxcDiagnostic;
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule, AstNode};
+
+#[derive(Debug, Default, Clone)]
+pub struct NoConfusingNonNullAssertion;
+
+declare_oxc_lint!(
+    /// ### What it does
+    /// Disallow non-null assertion in locations that may be confusing.
+    ///
+    /// ### Why is this bad?
+    /// Using a non-null assertion (!) next to an assign or equals check (= or == or ===) creates code that is confusing as it looks similar to a not equals check (!= !==).
+    ///
+    /// ### Example
+    /// ```javascript
+    ///    a! == b; // a non-null assertions(`!`) and an equals test(`==`)
+    ///    a !== b; // not equals test(`!==`)
+    ///    a! === b; // a non-null assertions(`!`) and an triple equals test(`===`)
+    /// ```
+    NoConfusingNonNullAssertion,
+    suspicious,
+    // See <https://oxc.rs/docs/contribute/linter.html#rule-category> for details
+);
+
+fn not_need_no_confusing_non_null_assertion_diagnostic(op_str: &str, span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::warn(format!(
+            "typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like \"a! {op_str} b\", which looks very similar to not equal \"a !{op_str} b\"."
+    ))
+    .with_help("Remove the \"!\", or prefix the \"=\" with it.")
+    .with_label(span)
+}
+
+fn wrap_up_no_confusing_non_null_assertion_diagnostic(span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::warn(
+        "typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like \"a! = b\", which looks very similar to not equal \"a != b\"."
+    )
+    .with_help("Wrap left-hand side in parentheses to avoid putting non-null assertion \"!\" and \"=\" together.")
+    .with_label(span)
+}
+
+fn get_depth_ends_in_bang(expr: &Expression<'_>) -> Option<u32> {
+    match expr {
+        Expression::TSNonNullExpression(_) => Some(0),
+        Expression::BinaryExpression(binary_expr) => {
+            get_depth_ends_in_bang(&binary_expr.right).map(|x| x + 1)
+        }
+        Expression::UnaryExpression(unary_expr) => {
+            get_depth_ends_in_bang(&unary_expr.argument).map(|x| x + 1)
+        }
+        Expression::AssignmentExpression(assignment_expr) => {
+            get_depth_ends_in_bang(&assignment_expr.right).map(|x| x + 1)
+        }
+        _ => None,
+    }
+}
+
+impl Rule for NoConfusingNonNullAssertion {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        match node.kind() {
+            AstKind::BinaryExpression(binary_expr) => {
+                let Some(bang_depth) = get_depth_ends_in_bang(&binary_expr.left) else {
+                    return;
+                };
+                if bang_depth == 0 {
+                    ctx.diagnostic(not_need_no_confusing_non_null_assertion_diagnostic(
+                        binary_expr.operator.as_str(),
+                        binary_expr.span,
+                    ));
+                } else {
+                    ctx.diagnostic(wrap_up_no_confusing_non_null_assertion_diagnostic(
+                        binary_expr.span,
+                    ));
+                }
+            }
+            AstKind::AssignmentExpression(assignment_expr) => {
+                let Some(simple_target) = assignment_expr.left.as_simple_assignment_target() else {
+                    return;
+                };
+                let SimpleAssignmentTarget::TSNonNullExpression(_) = simple_target else { return };
+                ctx.diagnostic(not_need_no_confusing_non_null_assertion_diagnostic(
+                    assignment_expr.operator.as_str(),
+                    assignment_expr.span,
+                ));
+            }
+            _ => {}
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec!["a == b!;", "a = b!;", "a !== b;", "a != b;", "(a + b!) == c;"]; // "(a + b!) = c;"]; that's a parse error??
+    let fail = vec![
+        "a! == b;",
+        "a! === b;",
+        "a + b! == c;",
+        "(obj = new new OuterObj().InnerObj).Name! == c;",
+        "(a==b)! ==c;",
+        "a! = b;",
+        "(obj = new new OuterObj().InnerObj).Name! = c;",
+        "(a=b)! =c;",
+    ];
+    // let fix = vec![
+    //     // source, expected, rule_config?
+    //     // ("f = 1 + d! == 2", "f = (1 + d!) == 2", None), TODO: Add suggest or the weird ;() fix
+    //     // ("f =  d! == 2", "f = d == 2", None), TODO: Add suggest remove bang
+    // ];
+    Tester::new(NoConfusingNonNullAssertion::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/no_confusing_non_null_assertion.snap

@@ -0,0 +1,58 @@
+---
+source: crates/oxc_linter/src/tester.rs
+---
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! == b", which looks very similar to not equal "a !== b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ a! == b;
+   · ───────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! === b", which looks very similar to not equal "a !=== b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ a! === b;
+   · ────────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! = b", which looks very similar to not equal "a != b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ a + b! == c;
+   · ───────────
+   ╰────
+  help: Wrap left-hand side in parentheses to avoid putting non-null assertion "!" and "=" together.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! == b", which looks very similar to not equal "a !== b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ (obj = new new OuterObj().InnerObj).Name! == c;
+   · ──────────────────────────────────────────────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! == b", which looks very similar to not equal "a !== b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ (a==b)! ==c;
+   · ───────────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! = b", which looks very similar to not equal "a != b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ a! = b;
+   · ──────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! = b", which looks very similar to not equal "a != b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ (obj = new new OuterObj().InnerObj).Name! = c;
+   · ─────────────────────────────────────────────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.
+
+  ⚠ typescript-eslint(no-confusing-non-null-assertion): Confusing combinations of non-null assertion and equal test like "a! = b", which looks very similar to not equal "a != b".
+   ╭─[no_confusing_non_null_assertion.tsx:1:1]
+ 1 │ (a=b)! =c;
+   · ─────────
+   ╰────
+  help: Remove the "!", or prefix the "=" with it.