From 0bf0b1765e4c582100a8355ea96195b3b0275bd5 Mon Sep 17 00:00:00 2001
From: Lauren Tan <poteto@users.noreply.github.com>
Date: Fri, 16 Aug 2024 17:37:44 -0400
Subject: [PATCH] [compiler] Surface unused opt out directives in eslint

This PR updates the eslint plugin to report unused opt out directives.
One of the downsides of the opt out directive is that it opts the
component/hook out of compilation forever, even if the underlying issue
was fixed in product code or fixed in the compiler.

ghstack-source-id: 81deb5c11b7c57f07f6ab13266066cd73b2f3729
Pull Request resolved: https://github.com/facebook/react/pull/30721
---
 .../__tests__/ReactCompilerRule-test.ts       | 59 +++++++++++++++++++
 .../src/rules/ReactCompilerRule.ts            | 51 +++++++++++++++-
 2 files changed, 109 insertions(+), 1 deletion(-)

diff --git a/compiler/packages/eslint-plugin-react-compiler/__tests__/ReactCompilerRule-test.ts b/compiler/packages/eslint-plugin-react-compiler/__tests__/ReactCompilerRule-test.ts
index c1aba9f4c8405..71be6b6622eb5 100644
--- a/compiler/packages/eslint-plugin-react-compiler/__tests__/ReactCompilerRule-test.ts
+++ b/compiler/packages/eslint-plugin-react-compiler/__tests__/ReactCompilerRule-test.ts
@@ -215,6 +215,65 @@ const tests: CompilerTestCases = {
         },
       ],
     },
+    {
+      name: "'use no forget' does not disable eslint rule",
+      code: normalizeIndent`
+        let count = 0;
+        function Component() {
+          'use no forget';
+          count = count + 1;
+          return <div>Hello world {count}</div>
+        }
+      `,
+      errors: [
+        {
+          message:
+            'Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render)',
+        },
+      ],
+    },
+    {
+      name: "Unused 'use no forget' directive is reported when no errors are present on components",
+      code: normalizeIndent`
+        function Component() {
+          'use no forget';
+          return <div>Hello world</div>
+        }
+      `,
+      errors: [
+        {
+          message: "Unused 'use no forget' directive",
+          suggestions: [
+            {
+              output:
+                // yuck
+                '\nfunction Component() {\n  \n  return <div>Hello world</div>\n}\n',
+            },
+          ],
+        },
+      ],
+    },
+    {
+      name: "Unused 'use no forget' directive is reported when no errors are present on non-components or hooks",
+      code: normalizeIndent`
+        function notacomponent() {
+          'use no forget';
+          return 1 + 1;
+        }
+      `,
+      errors: [
+        {
+          message: "Unused 'use no forget' directive",
+          suggestions: [
+            {
+              output:
+                // yuck
+                '\nfunction notacomponent() {\n  \n  return 1 + 1;\n}\n',
+            },
+          ],
+        },
+      ],
+    },
   ],
 };
 
diff --git a/compiler/packages/eslint-plugin-react-compiler/src/rules/ReactCompilerRule.ts b/compiler/packages/eslint-plugin-react-compiler/src/rules/ReactCompilerRule.ts
index 7b6525842c4d2..0a0956ebe1db0 100644
--- a/compiler/packages/eslint-plugin-react-compiler/src/rules/ReactCompilerRule.ts
+++ b/compiler/packages/eslint-plugin-react-compiler/src/rules/ReactCompilerRule.ts
@@ -15,10 +15,12 @@ import BabelPluginReactCompiler, {
   ErrorSeverity,
   parsePluginOptions,
   validateEnvironmentConfig,
+  OPT_OUT_DIRECTIVES,
   type PluginOptions,
 } from 'babel-plugin-react-compiler/src';
 import {Logger} from 'babel-plugin-react-compiler/src/Entrypoint';
 import type {Rule} from 'eslint';
+import {Statement} from 'estree';
 import * as HermesParser from 'hermes-parser';
 
 type CompilerErrorDetailWithLoc = Omit<CompilerErrorDetailOptions, 'loc'> & {
@@ -146,6 +148,7 @@ const rule: Rule.RuleModule = {
         userOpts['__unstable_donotuse_reportAllBailouts'];
     }
 
+    let shouldReportUnusedOptOutDirective = true;
     const options: PluginOptions = {
       ...parsePluginOptions(userOpts),
       ...COMPILER_OPTIONS,
@@ -155,6 +158,7 @@ const rule: Rule.RuleModule = {
       logEvent: (filename, event): void => {
         userLogger?.logEvent(filename, event);
         if (event.kind === 'CompileError') {
+          shouldReportUnusedOptOutDirective = false;
           const detail = event.detail;
           const suggest = makeSuggestions(detail);
           if (__unstable_donotuse_reportAllBailouts && event.fnLoc != null) {
@@ -272,7 +276,52 @@ const rule: Rule.RuleModule = {
         /* errors handled by injected logger */
       }
     }
-    return {};
+
+    function reportUnusedOptOutDirective(stmt: Statement) {
+      if (
+        stmt.type === 'ExpressionStatement' &&
+        stmt.expression.type === 'Literal' &&
+        typeof stmt.expression.value === 'string' &&
+        OPT_OUT_DIRECTIVES.has(stmt.expression.value) &&
+        stmt.loc != null
+      ) {
+        context.report({
+          message: `Unused '${stmt.expression.value}' directive`,
+          loc: stmt.loc,
+          suggest: [
+            {
+              desc: 'Remove the directive',
+              fix(fixer) {
+                return fixer.remove(stmt);
+              },
+            },
+          ],
+        });
+      }
+    }
+    if (shouldReportUnusedOptOutDirective) {
+      return {
+        FunctionDeclaration(fnDecl) {
+          for (const stmt of fnDecl.body.body) {
+            reportUnusedOptOutDirective(stmt);
+          }
+        },
+        ArrowFunctionExpression(fnExpr) {
+          if (fnExpr.body.type === 'BlockStatement') {
+            for (const stmt of fnExpr.body.body) {
+              reportUnusedOptOutDirective(stmt);
+            }
+          }
+        },
+        FunctionExpression(fnExpr) {
+          for (const stmt of fnExpr.body.body) {
+            reportUnusedOptOutDirective(stmt);
+          }
+        },
+      };
+    } else {
+      return {};
+    }
   },
 };