refactor(linter): add fixer for typescript-eslint/no-non-null-asserted-optional-chain (#9993)

Adds fixes for the `typescript-eslint/no-non-null-asserted-optional-chain` rule in the linter and adds better diagnostic messages with labeled spans.

Author: camchenry

Diff for: crates/oxc_language_server/src/linter/snapshots/fixtures_linter_issue_9958_issue.ts.snap

@@ -15,14 +15,26 @@ tags: None
 
 code: "typescript-eslint(no-non-null-asserted-optional-chain)"
 code_description.href: "https://oxc.rs/docs/guide/usage/linter/rules/typescript_eslint/no-non-null-asserted-optional-chain"
-message: "non-null assertions after an optional chain expression\nhelp: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion."
-range: Range { start: Position { line: 11, character: 18 }, end: Position { line: 11, character: 18 } }
-related_information[0].message: ""
+message: "Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.\nhelp: Remove the non-null assertion."
+range: Range { start: Position { line: 11, character: 18 }, end: Position { line: 11, character: 19 } }
+related_information[0].message: "non-null assertion made after optional chain"
 related_information[0].location.uri: "file://<variable>/fixtures/linter/issue_9958/issue.ts"
-related_information[0].location.range: Range { start: Position { line: 11, character: 18 }, end: Position { line: 11, character: 18 } }
-related_information[1].message: ""
+related_information[0].location.range: Range { start: Position { line: 11, character: 21 }, end: Position { line: 11, character: 22 } }
+related_information[1].message: "optional chain used"
 related_information[1].location.uri: "file://<variable>/fixtures/linter/issue_9958/issue.ts"
-related_information[1].location.range: Range { start: Position { line: 11, character: 21 }, end: Position { line: 11, character: 21 } }
+related_information[1].location.range: Range { start: Position { line: 11, character: 18 }, end: Position { line: 11, character: 19 } }
 severity: Some(Error)
 source: Some("oxc")
 tags: None
+            
+
+code: "None"
+code_description.href: "None"
+message: "non-null assertion made after optional chain"
+range: Range { start: Position { line: 11, character: 21 }, end: Position { line: 11, character: 22 } }
+related_information[0].message: "original diagnostic"
+related_information[0].location.uri: "file://<variable>/fixtures/linter/issue_9958/issue.ts"
+related_information[0].location.range: Range { start: Position { line: 11, character: 18 }, end: Position { line: 11, character: 19 } }
+severity: Some(Hint)
+source: Some("oxc")
+tags: None

Diff for: crates/oxc_linter/src/rules/typescript/no_non_null_asserted_optional_chain.rs

@@ -12,10 +12,14 @@ use crate::{
     rule::Rule,
 };
 
-fn no_non_null_asserted_optional_chain_diagnostic(span: Span, span1: Span) -> OxcDiagnostic {
-    OxcDiagnostic::warn("non-null assertions after an optional chain expression")
-        .with_help("Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.")
-        .with_labels([span, span1])
+fn no_non_null_asserted_optional_chain_diagnostic(
+    chain_span: Span,
+    assertion_span: Span,
+) -> OxcDiagnostic {
+    OxcDiagnostic::warn("Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.")
+        .with_help("Remove the non-null assertion.")
+        .with_label(assertion_span.primary_label("non-null assertion made after optional chain"))
+        .and_label(chain_span.label("optional chain used"))
 }
 
 #[derive(Debug, Default, Clone)]
@@ -27,20 +31,35 @@ declare_oxc_lint!(
     /// Disallow non-null assertions after an optional chain expression.
     ///
     /// ### Why is this bad?
-    /// `?.` optional chain expressions provide undefined if an object is null or undefined.
-    /// Using a `!` non-null assertion to assert the result of an `?.` optional chain expression is non-nullable is likely wrong.
     ///
-    /// Most of the time, either the object was not nullable and did not need the `?.` for its property lookup, or the `!` is incorrect and introducing a type safety hole.
+    /// By design, optional chain expressions (`?.`) provide `undefined` as the expression's value, if the object being
+    /// accessed is `null` or `undefined`, instead of throwing an error. Using a non-null assertion (`!`) to assert the
+    /// result of an optional chain expression is contradictory and likely wrong, as it indicates the code is both expecting
+    /// the value to be potentially `null` or `undefined` and non-null at the same time.
+    ///
+    /// In most cases, either:
+    /// 1. The object is not nullable and did not need the `?.` for its property lookup
+    /// 2. The non-null assertion is incorrect and introduces a type safety hole.
+    ///
+    /// ### Examples
+    ///
+    /// Examples of **incorrect** code for this rule:
     ///
-    /// ### Example
     /// ```ts
     /// foo?.bar!;
     /// foo?.bar()!;
     /// ```
+    ///
+    /// Examples of **correct** code for this rule:
+    ///
+    /// ```ts
+    /// foo?.bar;
+    /// foo.bar!;
+    /// ```
     NoNonNullAssertedOptionalChain,
     typescript,
     correctness,
-    pending
+    fix
 );
 
 impl Rule for NoNonNullAssertedOptionalChain {
@@ -90,10 +109,14 @@ impl Rule for NoNonNullAssertedOptionalChain {
         if let Some(chain_span) = chain_span {
             let chain_span_end = chain_span.end;
             let non_null_end = non_null_expr.span.end - 1;
-            ctx.diagnostic(no_non_null_asserted_optional_chain_diagnostic(
-                Span::new(chain_span_end, chain_span_end),
-                Span::new(non_null_end, non_null_end),
-            ));
+            let diagnostic = no_non_null_asserted_optional_chain_diagnostic(
+                Span::sized(chain_span_end, 1),
+                Span::sized(non_null_end, 1),
+            );
+            // ctx.diagnostic(diagnostic);
+            ctx.diagnostic_with_fix(diagnostic, |fixer| {
+                fixer.delete_range(Span::sized(non_null_end, 1))
+            });
         }
     }
 
@@ -143,11 +166,24 @@ fn test() {
         "(foo?.bar!)()",
     ];
 
+    let fix = vec![
+        ("foo?.bar!", "foo?.bar"),
+        ("foo?.['bar']!", "foo?.['bar']"),
+        ("foo?.bar()!", "foo?.bar()"),
+        ("(foo?.bar)!.baz", "(foo?.bar).baz"),
+        ("(foo?.bar)!().baz", "(foo?.bar)().baz"),
+        ("(foo?.bar)!", "(foo?.bar)"),
+        ("(foo?.bar)!()", "(foo?.bar)()"),
+        ("(foo?.bar!)", "(foo?.bar)"),
+        ("(foo?.bar!)()", "(foo?.bar)()"),
+    ];
+
     Tester::new(
         NoNonNullAssertedOptionalChain::NAME,
         NoNonNullAssertedOptionalChain::PLUGIN,
         pass,
         fail,
     )
+    .expect_fix(fix)
     .test_and_snapshot();
 }

Diff for: crates/oxc_linter/src/snapshots/typescript_no_non_null_asserted_optional_chain.snap

@@ -1,72 +1,92 @@
 ---
 source: crates/oxc_linter/src/tester.rs
 ---
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:4]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:9]
  1 │ foo?.bar!;
-   ·    ▲    ▲
+   ·    ┬    ┬
+   ·    │    ╰── non-null assertion made after optional chain
+   ·    ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:4]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:13]
  1 │ foo?.['bar']!;
-   ·    ▲        ▲
+   ·    ┬        ┬
+   ·    │        ╰── non-null assertion made after optional chain
+   ·    ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:4]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:11]
  1 │ foo?.bar()!;
-   ·    ▲      ▲
+   ·    ┬      ┬
+   ·    │      ╰── non-null assertion made after optional chain
+   ·    ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:8]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:12]
  1 │ foo.bar?.()!;
-   ·        ▲   ▲
+   ·        ┬   ┬
+   ·        │   ╰── non-null assertion made after optional chain
+   ·        ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:5]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:11]
  1 │ (foo?.bar)!.baz
-   ·     ▲     ▲
+   ·     ┬     ┬
+   ·     │     ╰── non-null assertion made after optional chain
+   ·     ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:5]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:11]
  1 │ (foo?.bar)!().baz
-   ·     ▲     ▲
+   ·     ┬     ┬
+   ·     │     ╰── non-null assertion made after optional chain
+   ·     ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:5]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:11]
  1 │ (foo?.bar)!
-   ·     ▲     ▲
+   ·     ┬     ┬
+   ·     │     ╰── non-null assertion made after optional chain
+   ·     ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:5]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:11]
  1 │ (foo?.bar)!()
-   ·     ▲     ▲
+   ·     ┬     ┬
+   ·     │     ╰── non-null assertion made after optional chain
+   ·     ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:5]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:10]
  1 │ (foo?.bar!)
-   ·     ▲    ▲
+   ·     ┬    ┬
+   ·     │    ╰── non-null assertion made after optional chain
+   ·     ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.
 
-  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): non-null assertions after an optional chain expression
-   ╭─[no_non_null_asserted_optional_chain.tsx:1:5]
+  ⚠ typescript-eslint(no-non-null-asserted-optional-chain): Optional chain expressions can return undefined by design: using a non-null assertion is unsafe and wrong.
+   ╭─[no_non_null_asserted_optional_chain.tsx:1:10]
  1 │ (foo?.bar!)()
-   ·     ▲    ▲
+   ·     ┬    ┬
+   ·     │    ╰── non-null assertion made after optional chain
+   ·     ╰── optional chain used
    ╰────
-  help: Optional chain expressions can return undefined by design - using a non-null assertion is unsafe and wrong. You should remove the non-null assertion.
+  help: Remove the non-null assertion.