typescript-eslint · nayounsang · Jun 5, 2025 · Jun 5, 2025 · Jun 5, 2025 · Jun 5, 2025
diff --git a/packages/eslint-plugin/docs/rules/prefer-optional-chain.mdx b/packages/eslint-plugin/docs/rules/prefer-optional-chain.mdx
@@ -265,6 +265,37 @@ thing?.toString();
 </TabItem>
 </Tabs>
 
+### `checkVoid`
+
+{/* insert option description */}
+
+Examples of code for this rule with `{ checkVoid: true }`:
+
+<Tabs>
+<TabItem value="❌ Incorrect">
+
+```ts option='{ "checkVoid": true }'
+declare const thing: {
+  method: undefined | (() => void);
+};
+
+thing.method && thing.method();
+```
+
+</TabItem>
+<TabItem value="✅ Correct">
+
+```ts option='{ "checkVoid": true }'
+declare const thing: {
+  method: undefined | (() => void);
+};
+
+thing.method?.();
+```
+
+</TabItem>
+</Tabs>
+
 ### `requireNullish`
 
 {/* insert option description */}

diff --git a/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/PreferOptionalChainOptions.ts b/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/PreferOptionalChainOptions.ts
@@ -10,5 +10,6 @@ export interface PreferOptionalChainOptions {
   checkNumber?: boolean;
   checkString?: boolean;
   checkUnknown?: boolean;
+  checkVoid?: boolean;
   requireNullish?: boolean;
 }
diff --git a/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/gatherLogicalOperands.ts b/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/gatherLogicalOperands.ts
@@ -59,8 +59,6 @@ export interface InvalidOperand {
   type: OperandValidity.Invalid;
 }
 type Operand = InvalidOperand | ValidOperand;
-
-const NULLISH_FLAGS = ts.TypeFlags.Null | ts.TypeFlags.Undefined;
 function isValidFalseBooleanCheckType(
   node: TSESTree.Node,
   disallowFalseyLiteral: boolean,
@@ -92,26 +90,30 @@ function isValidFalseBooleanCheckType(
     return false;
   }
 
-  let allowedFlags = NULLISH_FLAGS | ts.TypeFlags.Object;
-  if (options.checkAny === true) {
-    allowedFlags |= ts.TypeFlags.Any;
+  let flagsToExcludeFromCheck = 0;
+  if (options.checkAny !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.Any;
+  }
+  if (options.checkUnknown !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.Unknown;
   }
-  if (options.checkUnknown === true) {
-    allowedFlags |= ts.TypeFlags.Unknown;
+  if (options.checkString !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.StringLike;
   }
-  if (options.checkString === true) {
-    allowedFlags |= ts.TypeFlags.StringLike;
+  if (options.checkNumber !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.NumberLike;
   }
-  if (options.checkNumber === true) {
-    allowedFlags |= ts.TypeFlags.NumberLike;
+  if (options.checkBoolean !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.BooleanLike;
   }
-  if (options.checkBoolean === true) {
-    allowedFlags |= ts.TypeFlags.BooleanLike;
+  if (options.checkBigInt !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.BigIntLike;
   }
-  if (options.checkBigInt === true) {
-    allowedFlags |= ts.TypeFlags.BigIntLike;
+  if (options.checkVoid !== true) {
+    flagsToExcludeFromCheck |= ts.TypeFlags.Void;
   }
-  return types.every(t => isTypeFlagSet(t, allowedFlags));
+
+  return types.every(t => !isTypeFlagSet(t, flagsToExcludeFromCheck));
 }
 
 export function gatherLogicalOperands(

diff --git a/packages/eslint-plugin/src/rules/prefer-optional-chain.ts b/packages/eslint-plugin/src/rules/prefer-optional-chain.ts
@@ -82,6 +82,11 @@ export default createRule<
             description:
               'Check operands that are typed as `unknown` when inspecting "loose boolean" operands.',
           },
+          checkVoid: {
+            type: 'boolean',
+            description:
+              'Check operands that are typed as `void` when inspecting "loose boolean" operands.',
+          },
           requireNullish: {
             type: 'boolean',
             description:
@@ -100,6 +105,7 @@ export default createRule<
       checkNumber: true,
       checkString: true,
       checkUnknown: true,
+      checkVoid: true,
       requireNullish: false,
     },
   ],

diff --git a/packages/eslint-plugin/tests/docs-eslint-output-snapshots/prefer-optional-chain.shot b/packages/eslint-plugin/tests/docs-eslint-output-snapshots/prefer-optional-chain.shot
diff --git a/packages/eslint-plugin/tests/rules/prefer-optional-chain/prefer-optional-chain.test.ts b/packages/eslint-plugin/tests/rules/prefer-optional-chain/prefer-optional-chain.test.ts
@@ -1680,6 +1680,48 @@ describe('hand-crafted cases', () => {
         ],
         output: 'a?.prop;',
       },
+      // check void
+      {
+        code: `
+declare const foo: {
+  method: undefined | (() => void);
+};
+foo.method && foo.method();
+        `,
+        errors: [{ messageId: 'preferOptionalChain' }],
+        output: `
+declare const foo: {
+  method: undefined | (() => void);
+};
+foo.method?.();
+        `,
+      },
+      // Exclude for everything else, an error occurs
+      {
+        code: noFormat`declare const foo: { x: { y: string } } | null; foo && foo.x;`,
+        errors: [
+          {
+            messageId: 'preferOptionalChain',
+            suggestions: [
+              {
+                messageId: 'optionalChainSuggest',
+                output: `declare const foo: { x: { y: string } } | null; foo?.x;`,
+              },
+            ],
+          },
+        ],
+        options: [
+          {
+            checkAny: false,
+            checkBigInt: false,
+            checkBoolean: false,
+            checkNumber: false,
+            checkString: false,
+            checkUnknown: false,
+            checkVoid: false,
+          },
+        ],
+      },
     ],
     valid: [
       '!a || !b;',
@@ -1878,6 +1920,15 @@ describe('hand-crafted cases', () => {
         `,
         options: [{ checkUnknown: false }],
       },
+      {
+        code: `
+declare const foo: {
+  method: undefined | (() => void);
+};
+foo.method && foo.method();
+        `,
+        options: [{ checkVoid: false }],
+      },
       '(x = {}) && (x.y = true) != null && x.y.toString();',
       "('x' as `${'x'}`) && ('x' as `${'x'}`).length;",
       '`x` && `x`.length;',

diff --git a/packages/eslint-plugin/tests/schema-snapshots/prefer-optional-chain.shot b/packages/eslint-plugin/tests/schema-snapshots/prefer-optional-chain.shot