From 67f600df1379b725cc1d3e97b837533de34124a5 Mon Sep 17 00:00:00 2001
From: Lauren Tan <poteto@users.noreply.github.com>
Date: Wed, 19 Oct 2022 12:55:10 -0400
Subject: [PATCH] [useEvent] Lint for presence of useEvent functions in
 dependency lists

With #25473, the identity of useEvent's return value is no longer stable
across renders. Previously, the ExhaustiveDeps lint rule would only
allow the omission of the useEvent function, but you could still add it
as a dependency.

This PR updates the ExhaustiveDeps rule to explicitly check for the
presence of useEvent functions in dependency lists, and emits a warning
and suggestion/autofixer for removing the dependency.
---
 .../ESLintRuleExhaustiveDeps-test.js          | 57 ++++++++++++++++---
 .../src/ExhaustiveDeps.js                     | 27 ++++++++-
 2 files changed, 74 insertions(+), 10 deletions(-)

diff --git a/packages/eslint-plugin-react-hooks/__tests__/ESLintRuleExhaustiveDeps-test.js b/packages/eslint-plugin-react-hooks/__tests__/ESLintRuleExhaustiveDeps-test.js
index fc343705a6922..c4c379e8b4e63 100644
--- a/packages/eslint-plugin-react-hooks/__tests__/ESLintRuleExhaustiveDeps-test.js
+++ b/packages/eslint-plugin-react-hooks/__tests__/ESLintRuleExhaustiveDeps-test.js
@@ -7635,15 +7635,54 @@ if (__EXPERIMENTAL__) {
     ...tests.valid,
     {
       code: normalizeIndent`
-      function MyComponent({ theme }) {
-        const onStuff = useEvent(() => {
-          showNotification(theme);
-        });
-        useEffect(() => {
-          onStuff();
-        }, []);
-      }
-    `,
+        function MyComponent({ theme }) {
+          const onStuff = useEvent(() => {
+            showNotification(theme);
+          });
+          useEffect(() => {
+            onStuff();
+          }, []);
+        }
+      `,
+    },
+  ];
+
+  tests.invalid = [
+    ...tests.invalid,
+    {
+      code: normalizeIndent`
+        function MyComponent({ theme }) {
+          const onStuff = useEvent(() => {
+            showNotification(theme);
+          });
+          useEffect(() => {
+            onStuff();
+          }, [onStuff]);
+        }
+      `,
+      errors: [
+        {
+          message:
+            '`useEvent` functions always return a new identity for every render. This means that ' +
+            'it should not be included in dependency lists, as it would cause the callback to be ' +
+            'run on every render. You can safely remove this.',
+          suggestions: [
+            {
+              desc: 'Remove the dependency `onStuff`',
+              output: normalizeIndent`
+                function MyComponent({ theme }) {
+                  const onStuff = useEvent(() => {
+                    showNotification(theme);
+                  });
+                  useEffect(() => {
+                    onStuff();
+                  }, []);
+                }
+              `,
+            },
+          ],
+        },
+      ],
     },
   ];
 }
diff --git a/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js b/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js
index 6f99e6ef4369e..fc5f2d0127478 100644
--- a/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js
+++ b/packages/eslint-plugin-react-hooks/src/ExhaustiveDeps.js
@@ -74,6 +74,7 @@ export default {
     const stateVariables = new WeakSet();
     const stableKnownValueCache = new WeakMap();
     const functionWithoutCapturedValueCache = new WeakMap();
+    const useEventVariables = new WeakSet();
     function memoizeWithWeakMap(fn, map) {
       return function(arg) {
         if (map.has(arg)) {
@@ -226,7 +227,12 @@ export default {
           // useRef() return value is stable.
           return true;
         } else if (isUseEventIdentifier(callee) && id.type === 'Identifier') {
-          // useEvent() return value is stable.
+          for (const ref of resolved.references) {
+            if (ref !== id) {
+              useEventVariables.add(ref.identifier);
+            }
+          }
+          // useEvent() return value is always unstable.
           return true;
         } else if (name === 'useState' || name === 'useReducer') {
           // Only consider second value in initializing tuple stable.
@@ -639,6 +645,25 @@ export default {
             });
             return;
           }
+          if (useEventVariables.has(declaredDependencyNode)) {
+            reportProblem({
+              node: declaredDependencyNode,
+              message:
+                '`useEvent` functions always return a new identity for every render. This means ' +
+                'that it should not be included in dependency lists, as it would cause the ' +
+                'callback to be run on every render. You can safely remove this.',
+              suggest: [
+                {
+                  desc: `Remove the dependency \`${context.getSource(
+                    declaredDependencyNode,
+                  )}\``,
+                  fix(fixer) {
+                    return fixer.removeRange(declaredDependencyNode.range);
+                  },
+                },
+              ],
+            });
+          }
           // Try to normalize the declared dependency. If we can't then an error
           // will be thrown. We will catch that error and report an error.
           let declaredDependency;