fix(linter): add help guidance to eslint diagnostic messages (#19562)

Partially addresses #19121

Add `.with_help()` to 4 ESLint rule diagnostics to help developers understand how to resolve warnings:

- `no-undef`: "Either define '{name}' or remove the reference to it. If '{name}' is a global variable, add it to the 'globals' configuration."
- `no-setter-return`: "Remove the return statement or ensure it does not return a value."
- `no-unreachable`: "Remove the unreachable code or fix the control flow to make it reachable."

---------

Co-authored-by: Cameron <cameron.clark@hey.com>

Author: anthonyamaro15

apps/oxlint/src/snapshots/_-W no-undef -c fixtures__eslintrc_env__eslintrc_no_env.json fixtures__eslintrc_env__test.js@oxlint.snap

@@ -11,6 +11,7 @@ working directory:
  1 | console.log('')
    : ^^^^^^^
    `----
+  help: Either define 'console' or remove the reference to it. If 'console' is a global variable, add it to the 'globals' configuration.
 
 Found 1 warning and 0 errors.
 Finished in <variable>ms on 1 file with 94 rules using 1 threads.

apps/oxlint/src/snapshots/_-W no-undef -c fixtures__no_undef__eslintrc.json fixtures__no_undef__test.js@oxlint.snap

@@ -11,6 +11,7 @@ working directory:
  1 | console.log(foo)
    : ^^^^^^^
    `----
+  help: Either define 'console' or remove the reference to it. If 'console' is a global variable, add it to the 'globals' configuration.
 
 Found 1 warning and 0 errors.
 Finished in <variable>ms on 1 file with 94 rules using 1 threads.

crates/oxc_linter/src/rules/eslint/no_setter_return.rs

@@ -6,7 +6,9 @@ use oxc_span::Span;
 use crate::{AstNode, context::LintContext, rule::Rule};
 
 fn no_setter_return_diagnostic(span: Span) -> OxcDiagnostic {
-    OxcDiagnostic::warn("Setter cannot return a value").with_label(span)
+    OxcDiagnostic::warn("Setter cannot return a value")
+        .with_help("Remove the return statement or ensure it does not return a value.")
+        .with_label(span)
 }
 
 #[derive(Debug, Default, Clone)]

crates/oxc_linter/src/rules/eslint/no_undef.rs

@@ -13,7 +13,11 @@ use crate::{
 };
 
 fn no_undef_diagnostic(name: &str, span: Span) -> OxcDiagnostic {
-    OxcDiagnostic::warn(format!("'{name}' is not defined.")).with_label(span)
+    OxcDiagnostic::warn(format!("'{name}' is not defined."))
+        .with_help(format!(
+            "Either define '{name}' or remove the reference to it. If '{name}' is a global variable, add it to the 'globals' configuration."
+        ))
+        .with_label(span)
 }
 
 #[derive(Debug, Default, Clone, JsonSchema, Deserialize)]

crates/oxc_linter/src/rules/eslint/no_unreachable.rs

@@ -14,7 +14,9 @@ use oxc_span::{GetSpan, Span};
 use crate::{context::LintContext, rule::Rule};
 
 fn no_unreachable_diagnostic(span: Span) -> OxcDiagnostic {
-    OxcDiagnostic::warn("Unreachable code.").with_label(span)
+    OxcDiagnostic::warn("Unreachable code.")
+        .with_help("Remove the unreachable code or fix the control flow to make it reachable.")
+        .with_label(span)
 }
 
 /// <https://github.com/eslint/eslint/blob/069aa680c78b8516b9a1b568519f1d01e74fb2a2/lib/rules/no-unreachable.js#L196>

crates/oxc_linter/src/snapshots/eslint_no_setter_return.snap

@@ -7,249 +7,291 @@ source: crates/oxc_linter/src/tester.rs
  1 │ ({ set a(val){ return val + 1; } })
    ·                ───────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:17]
  1 │ ({ set a(val) { return 1; } })
    ·                 ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:24]
  1 │ class A { set a(val) { return 1; } }
    ·                        ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:31]
  1 │ class A { static set a(val) { return 1; } }
    ·                               ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:23]
  1 │ (class { set a(val) { return 1; } })
    ·                       ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:17]
  1 │ ({ set a(val) { return val; } })
    ·                 ───────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:24]
  1 │ class A { set a(val) { return undefined; } }
    ·                        ─────────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:23]
  1 │ (class { set a(val) { return null; } })
    ·                       ────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:17]
  1 │ ({ set a(val) { return x + y; } })
    ·                 ─────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:24]
  1 │ class A { set a(val) { return foo(); } }
    ·                        ─────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:23]
  1 │ (class { set a(val) { return this._a; } })
    ·                       ───────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:17]
  1 │ ({ set a(val) { return this.a; } })
    ·                 ──────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:28]
  1 │ ({ set a(val) { if (foo) { return 1; }; } })
    ·                            ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:30]
  1 │ class A { set a(val) { try { return 1; } catch(e) {} } }
    ·                              ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:57]
  1 │ (class { set a(val) { while (foo){ if (bar) break; else return 1; } } })
    ·                                                         ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:17]
  1 │ ({ set a(val) { return 1; }, set b(val) { return 1; } })
    ·                 ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:43]
  1 │ ({ set a(val) { return 1; }, set b(val) { return 1; } })
    ·                                           ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:24]
  1 │ class A { set a(val) { return 1; } set b(val) { return 1; } }
    ·                        ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:49]
  1 │ class A { set a(val) { return 1; } set b(val) { return 1; } }
    ·                                                 ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:23]
  1 │ (class { set a(val) { return 1; } static set b(val) { return 1; } })
    ·                       ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:55]
  1 │ (class { set a(val) { return 1; } static set b(val) { return 1; } })
    ·                                                       ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:27]
  1 │ ({ set a(val) { if(val) { return 1; } else { return 2 }; } })
    ·                           ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:46]
  1 │ ({ set a(val) { if(val) { return 1; } else { return 2 }; } })
    ·                                              ────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:46]
  1 │ class A { set a(val) { switch(val) { case 1: return x; case 2: return y; default: return z } } }
    ·                                              ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:64]
  1 │ class A { set a(val) { switch(val) { case 1: return x; case 2: return y; default: return z } } }
    ·                                                                ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:83]
  1 │ class A { set a(val) { switch(val) { case 1: return x; case 2: return y; default: return z } } }
    ·                                                                                   ────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:62]
  1 │ (class { static set a(val) { if (val > 0) { this._val = val; return val; } return false; } })
    ·                                                              ───────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:76]
  1 │ (class { static set a(val) { if (val > 0) { this._val = val; return val; } return false; } })
    ·                                                                            ─────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:27]
  1 │ ({ set a(val) { if(val) { return 1; } else { return; }; } })
    ·                           ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:46]
  1 │ class A { set a(val) { switch(val) { case 1: return x; case 2: return; default: return z } } }
    ·                                              ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:81]
  1 │ class A { set a(val) { switch(val) { case 1: return x; case 2: return; default: return z } } }
    ·                                                                                 ────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:72]
  1 │ (class { static set a(val) { if (val > 0) { this._val = val; return; } return false; } })
    ·                                                                        ─────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:32]
  1 │ ({ set a(val) { function b(){} return b(); } })
    ·                                ───────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:24]
  1 │ class A { set a(val) { return () => {}; } }
    ·                        ────────────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:49]
  1 │ (class { set a(val) { function b(){ return 1; } return 2; } })
    ·                                                 ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:41]
  1 │ ({ set a(val) { function b(){ return; } return 1; } })
    ·                                         ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:58]
  1 │ class A { set a(val) { var x = function() { return 1; }; return 2; } }
    ·                                                          ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:50]
  1 │ (class { set a(val) { var x = () => { return; }; return 2; } })
    ·                                                  ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:33]
  1 │ function f(){}; ({ set a(val) { return 1; } });
    ·                                 ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:44]
  1 │ x = function f(){}; class A { set a(val) { return 1; } };
    ·                                            ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:40]
  1 │ x = () => {}; A = class { set a(val) { return 1; } };
    ·                                        ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.
 
   ⚠ eslint(no-setter-return): Setter cannot return a value
    ╭─[no_setter_return.js:1:25]
  1 │ return; ({ set a(val) { return 1; } }); return 2;
    ·                         ─────────
    ╰────
+  help: Remove the return statement or ensure it does not return a value.