From 66b1c1a1910c686c09e34b69c41132a4303379f7 Mon Sep 17 00:00:00 2001
From: mdm317 <dbswh1008@gmail.com>
Date: Fri, 17 Oct 2025 00:23:47 +0900
Subject: [PATCH 1/6] fix : remove isAlwaysTruthyOperand

---
 .../analyzeChain.ts                           |  61 +-
 .../prefer-optional-chain.test.ts             | 755 +++++-------------
 2 files changed, 206 insertions(+), 610 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts b/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts
index 84c1ca6e9593..e197e382f731 100644
--- a/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts
+++ b/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts
@@ -48,40 +48,6 @@ function includesType(
   return false;
 }
 
-function isAlwaysTruthyOperand(
-  comparedName: TSESTree.Node,
-  nullishComparisonType: NullishComparisonType,
-  parserServices: ParserServicesWithTypeInformation,
-): boolean {
-  const ANY_UNKNOWN_FLAGS = ts.TypeFlags.Any | ts.TypeFlags.Unknown;
-  const comparedNameType = parserServices.getTypeAtLocation(comparedName);
-
-  if (isTypeFlagSet(comparedNameType, ANY_UNKNOWN_FLAGS)) {
-    return false;
-  }
-  switch (nullishComparisonType) {
-    case NullishComparisonType.Boolean:
-    case NullishComparisonType.NotBoolean: {
-      const types = unionConstituents(comparedNameType);
-      return types.every(type => !isFalsyType(type));
-    }
-    case NullishComparisonType.NotStrictEqualUndefined:
-    case NullishComparisonType.NotStrictEqualNull:
-    case NullishComparisonType.StrictEqualNull:
-    case NullishComparisonType.StrictEqualUndefined:
-      return !isTypeFlagSet(
-        comparedNameType,
-        ts.TypeFlags.Null | ts.TypeFlags.Undefined,
-      );
-    case NullishComparisonType.NotEqualNullOrUndefined:
-    case NullishComparisonType.EqualNullOrUndefined:
-      return !isTypeFlagSet(
-        comparedNameType,
-        ts.TypeFlags.Null | ts.TypeFlags.Undefined,
-      );
-  }
-}
-
 function isValidAndLastChainOperand(
   ComparisonValueType: TSESTree.Node,
   comparisonType: ComparisonType,
@@ -710,20 +676,6 @@ export function analyzeChain(
             }
             break;
           }
-          case NullishComparisonType.StrictEqualNull:
-          case NullishComparisonType.NotStrictEqualNull: {
-            if (
-              comparisonResult === NodeComparisonResult.Subset &&
-              isAlwaysTruthyOperand(
-                lastOperand.comparedName,
-                lastOperand.comparisonType,
-                parserServices,
-              )
-            ) {
-              lastChain = operand;
-            }
-            break;
-          }
         }
       }
       maybeReportThenReset();
@@ -768,16 +720,11 @@ export function analyzeChain(
         : isValidOrLastChainOperand;
     if (
       comparisonResult === NodeComparisonResult.Subset &&
-      (isAlwaysTruthyOperand(
-        lastOperand.comparedName,
-        lastOperand.comparisonType,
+      isValidLastChainOperand(
+        lastChainOperand.comparisonValue,
+        lastChainOperand.comparisonType,
         parserServices,
-      ) ||
-        isValidLastChainOperand(
-          lastChainOperand.comparisonValue,
-          lastChainOperand.comparisonType,
-          parserServices,
-        ))
+      )
     ) {
       lastChain = lastChainOperand;
     }
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
index a990d70b60bb..6336aabe0f44 100644
--- 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
@@ -864,441 +864,12 @@ describe('chain ending with comparison', () => {
       {
         code: `
           declare const foo: { bar: number };
-          foo && foo.bar == x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar == null;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == null;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar == undefined;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == undefined;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar === x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar === x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar === undefined;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar === undefined;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== 0;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== 0;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== 1;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== 1;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== '123';
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== '123';
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== {};
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== {};
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== false;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== false;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== true;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== true;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== null;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== null;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar !== x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != 0;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != 0;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != 1;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != 1;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != '123';
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != '123';
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != {};
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != {};
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != false;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != false;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != true;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != true;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != null;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != null;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo && foo.bar != x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar == x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar == null;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == null;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar == undefined;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == undefined;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar === x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar === x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar === undefined;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar === undefined;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== 0;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== 0;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== 1;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== 1;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== '123';
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== '123';
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== {};
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== {};
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== false;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== false;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== true;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== true;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== null;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== null;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar !== x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != 0;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != 0;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != 1;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != 1;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != '123';
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != '123';
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != {};
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != {};
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != false;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != false;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != true;
+          foo && foo.bar != null;
         `,
         errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
         output: `
           declare const foo: { bar: number };
-          foo?.bar != true;
+          foo?.bar != null;
         `,
       },
       {
@@ -1312,39 +883,6 @@ describe('chain ending with comparison', () => {
           foo?.bar != null;
         `,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo != null && foo.bar != x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number } | 1;
-          foo && foo.bar == x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number } | 1;
-          foo?.bar == x;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number } | 0;
-          foo != null && foo.bar == x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number } | 0;
-          foo?.bar == x;
-        `,
-      },
       {
         code: '!foo || foo.bar != 0;',
         errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
@@ -1505,17 +1043,6 @@ describe('chain ending with comparison', () => {
         errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
         output: `foo?.bar !== null;`,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          !foo || foo.bar == x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == x;
-        `,
-      },
       {
         code: `
           declare const foo: { bar: number };
@@ -1538,17 +1065,6 @@ describe('chain ending with comparison', () => {
           foo?.bar == undefined;
         `,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          !foo || foo.bar === x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar === x;
-        `,
-      },
       {
         code: `
           declare const foo: { bar: number };
@@ -1637,17 +1153,6 @@ describe('chain ending with comparison', () => {
           foo?.bar !== null;
         `,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          !foo || foo.bar !== x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== x;
-        `,
-      },
       {
         code: `
           declare const foo: { bar: number };
@@ -1714,40 +1219,6 @@ describe('chain ending with comparison', () => {
           foo?.bar != true;
         `,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          !foo || foo.bar != null;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != null;
-        `,
-      },
-      {
-        code: `
-          declare const foo: { bar: number };
-          !foo || foo.bar != x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar != x;
-        `,
-      },
-
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo == null || foo.bar == x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar == x;
-        `,
-      },
       {
         code: `
           declare const foo: { bar: number };
@@ -1770,17 +1241,6 @@ describe('chain ending with comparison', () => {
           foo?.bar == undefined;
         `,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo == null || foo.bar === x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar === x;
-        `,
-      },
       {
         code: `
           declare const foo: { bar: number };
@@ -1869,17 +1329,6 @@ describe('chain ending with comparison', () => {
           foo?.bar !== null;
         `,
       },
-      {
-        code: `
-          declare const foo: { bar: number };
-          foo == null || foo.bar !== x;
-        `,
-        errors: [{ messageId: 'preferOptionalChain', suggestions: null }],
-        output: `
-          declare const foo: { bar: number };
-          foo?.bar !== x;
-        `,
-      },
       // yoda case
       {
         code: "foo != null && null != foo.bar && '123' == foo.bar.baz;",
@@ -1938,6 +1387,174 @@ describe('chain ending with comparison', () => {
       'foo != null && foo.bar != false;',
       'foo != null && foo.bar != true;',
       'foo != null && foo.bar != x;',
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar == x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar == null;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar == undefined;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar === x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar === undefined;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== 0;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== 1;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== '123';
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== {};
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== false;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== true;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== null;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar !== x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != 0;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != 1;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != '123';
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != {};
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != false;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != true;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo && foo.bar != x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar == x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar == null;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar == undefined;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar === x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar === undefined;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== 0;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== 1;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== '123';
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== {};
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== false;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== true;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== null;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar !== x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != 0;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != 1;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != '123';
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != {};
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != false;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != true;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo != null && foo.bar != x;
+      `,
+      `
+        declare const foo: { bar: number } | 1;
+        foo && foo.bar == x;
+      `,
+      `
+        declare const foo: { bar: number } | 0;
+        foo != null && foo.bar == x;
+      `,
       `
         declare const foo: { bar: number } | null;
         foo && foo.bar == x;
@@ -2108,6 +1725,26 @@ describe('chain ending with comparison', () => {
         declare const foo: { bar: number } | undefined;
         foo !== undefined && foo !== undefined && foo.bar != 1;
       `,
+      `
+        declare const foo: { bar: number };
+        !foo || foo.bar == x;
+      `,
+      `
+        declare const foo: { bar: number };
+        !foo || foo.bar === x;
+      `,
+      `
+        declare const foo: { bar: number };
+        !foo || foo.bar !== x;
+      `,
+      `
+        declare const foo: { bar: number };
+        !foo || foo.bar != null;
+      `,
+      `
+        declare const foo: { bar: number };
+        !foo || foo.bar != x;
+      `,
       '!foo && foo.bar == 0;',
       '!foo && foo.bar == 1;',
       "!foo && foo.bar == '123';",
@@ -2176,6 +1813,18 @@ describe('chain ending with comparison', () => {
       '!foo || foo.bar == x;',
       '!foo || foo.bar !== x;',
       '!foo || foo.bar !== undefined;',
+      `
+        declare const foo: { bar: number };
+        foo == null || foo.bar == x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo == null || foo.bar === x;
+      `,
+      `
+        declare const foo: { bar: number };
+        foo == null || foo.bar !== x;
+      `,
       'foo == null || foo.bar != x;',
       'foo == null || foo.bar != null;',
       'foo == null || foo.bar != undefined;',

From a38269604521b035a9e117a24c41876229f275f9 Mon Sep 17 00:00:00 2001
From: mdm317 <dbswh1008@gmail.com>
Date: Fri, 17 Oct 2025 00:28:06 +0900
Subject: [PATCH 2/6] test : fix base case

---
 .../prefer-optional-chain.test.ts             | 80 -------------------
 1 file changed, 80 deletions(-)

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
index 6336aabe0f44..a81f48c55a3e 100644
--- 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
@@ -3138,7 +3138,6 @@ describe('base cases', () => {
             mutateCode: c => c.replaceAll('&&', '!== null &&'),
             mutateOutput: identity,
             operator: '&&',
-            skipIds: [20, 26],
           }),
           // but if the type is just `| null` - then it covers the cases and is
           // a valid conversion
@@ -3150,45 +3149,6 @@ describe('base cases', () => {
               operator: '&&',
               useSuggestionFixer: true,
             }),
-            {
-              code: `
-                declare const foo: {
-                  bar: () =>
-                    | { baz: { buzz: (() => number) | null | undefined } | null | undefined }
-                    | null
-                    | undefined;
-                };
-                foo.bar !== null &&
-                  foo.bar() !== null &&
-                  foo.bar().baz !== null &&
-                  foo.bar().baz.buzz !== null &&
-                  foo.bar().baz.buzz();
-              `,
-              errors: [{ messageId: 'preferOptionalChain' }],
-              output: `
-                declare const foo: {
-                  bar: () =>
-                    | { baz: { buzz: (() => number) | null | undefined } | null | undefined }
-                    | null
-                    | undefined;
-                };
-                foo.bar?.() !== null &&
-                  foo.bar().baz !== null &&
-                  foo.bar().baz.buzz !== null &&
-                  foo.bar().baz.buzz();
-              `,
-            },
-            {
-              code: `
-                declare const foo: { bar: () => { baz: number } | null | undefined };
-                foo.bar !== null && foo.bar?.() !== null && foo.bar?.().baz;
-              `,
-              errors: [{ messageId: 'preferOptionalChain' }],
-              output: `
-                declare const foo: { bar: () => { baz: number } | null | undefined };
-                foo.bar?.() !== null && foo.bar?.().baz;
-              `,
-            },
           ],
         });
       });
@@ -3303,7 +3263,6 @@ describe('base cases', () => {
             mutateCode: c => c.replaceAll('||', '=== null ||'),
             mutateOutput: identity,
             operator: '||',
-            skipIds: [20, 26],
           }),
           // but if the type is just `| null` - then it covers the cases and is
           // a valid conversion
@@ -3320,45 +3279,6 @@ describe('base cases', () => {
               operator: '||',
               useSuggestionFixer: true,
             }),
-            {
-              code: `
-                declare const foo: {
-                  bar: () =>
-                    | { baz: { buzz: (() => number) | null | undefined } | null | undefined }
-                    | null
-                    | undefined;
-                };
-                foo.bar === null ||
-                  foo.bar() === null ||
-                  foo.bar().baz === null ||
-                  foo.bar().baz.buzz === null ||
-                  foo.bar().baz.buzz();
-              `,
-              errors: [{ messageId: 'preferOptionalChain' }],
-              output: `
-                declare const foo: {
-                  bar: () =>
-                    | { baz: { buzz: (() => number) | null | undefined } | null | undefined }
-                    | null
-                    | undefined;
-                };
-                foo.bar?.() === null ||
-                  foo.bar().baz === null ||
-                  foo.bar().baz.buzz === null ||
-                  foo.bar().baz.buzz();
-              `,
-            },
-            {
-              code: `
-                declare const foo: { bar: () => { baz: number } | null | undefined };
-                foo.bar === null || foo.bar?.() === null || foo.bar?.().baz;
-              `,
-              errors: [{ messageId: 'preferOptionalChain' }],
-              output: `
-                declare const foo: { bar: () => { baz: number } | null | undefined };
-                foo.bar?.() === null || foo.bar?.().baz;
-              `,
-            },
           ],
         });
       });

From ca323edfffc2b644168b4c026a81242a19d6cbbc Mon Sep 17 00:00:00 2001
From: mdm317 <dbswh1008@gmail.com>
Date: Fri, 17 Oct 2025 00:46:09 +0900
Subject: [PATCH 3/6] test : add some case for array/index access

---
 .../prefer-optional-chain/prefer-optional-chain.test.ts   | 8 ++++++++
 1 file changed, 8 insertions(+)

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
index a81f48c55a3e..0c53b7b6332e 100644
--- 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
@@ -1877,6 +1877,14 @@ describe('chain ending with comparison', () => {
       'foo != null || foo.bar !== false;',
       'foo != null || foo.bar !== true;',
       'foo != null || foo.bar !== null;',
+      `
+        declare const record: Record<string, { kind: string }>;
+        record['key'] && record['key'].kind !== '1'
+      `,
+      `
+        declare const array: { b?: string }[];
+        !array[1] || array[1].b === "foo"
+      `,
     ],
   });
 });

From 87605b08ea91bb85acdca5ebfd4fc82126d2ec3c Mon Sep 17 00:00:00 2001
From: mdm317 <dbswh1008@gmail.com>
Date: Fri, 17 Oct 2025 01:20:17 +0900
Subject: [PATCH 4/6] fix : lint err

---
 .../src/rules/prefer-optional-chain-utils/analyzeChain.ts     | 2 +-
 .../rules/prefer-optional-chain/prefer-optional-chain.test.ts | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts b/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts
index e197e382f731..a2b11134e540 100644
--- a/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts
+++ b/packages/eslint-plugin/src/rules/prefer-optional-chain-utils/analyzeChain.ts
@@ -10,7 +10,7 @@ import type {
 } from '@typescript-eslint/utils/ts-eslint';
 
 import { AST_NODE_TYPES } from '@typescript-eslint/utils';
-import { isFalsyType, unionConstituents } from 'ts-api-utils';
+import { unionConstituents } from 'ts-api-utils';
 import * as ts from 'typescript';
 
 import type { LastChainOperand, ValidOperand } from './gatherLogicalOperands';
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
index 0c53b7b6332e..14367cfcf0d3 100644
--- 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
@@ -1879,11 +1879,11 @@ describe('chain ending with comparison', () => {
       'foo != null || foo.bar !== null;',
       `
         declare const record: Record<string, { kind: string }>;
-        record['key'] && record['key'].kind !== '1'
+        record['key'] && record['key'].kind !== '1';
       `,
       `
         declare const array: { b?: string }[];
-        !array[1] || array[1].b === "foo"
+        !array[1] || array[1].b === 'foo';
       `,
     ],
   });

From 837db2a44813a28089fca4d76f49e77f12266ca7 Mon Sep 17 00:00:00 2001
From: mdm317 <dbswh1008@gmail.com>
Date: Sat, 18 Oct 2025 02:24:35 +0900
Subject: [PATCH 5/6] refactor : undeclaredVar

---
 .../prefer-optional-chain.test.ts             | 78 +++++++++----------
 1 file changed, 39 insertions(+), 39 deletions(-)

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
index 14367cfcf0d3..946895825cf8 100644
--- 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
@@ -1347,10 +1347,10 @@ describe('chain ending with comparison', () => {
       },
     ],
     valid: [
-      'foo && foo.bar == x;',
+      'foo && foo.bar == undeclaredVar;',
       'foo && foo.bar == null;',
       'foo && foo.bar == undefined;',
-      'foo && foo.bar === x;',
+      'foo && foo.bar === undeclaredVar;',
       'foo && foo.bar === undefined;',
       'foo && foo.bar !== 0;',
       'foo && foo.bar !== 1;',
@@ -1359,18 +1359,18 @@ describe('chain ending with comparison', () => {
       'foo && foo.bar !== false;',
       'foo && foo.bar !== true;',
       'foo && foo.bar !== null;',
-      'foo && foo.bar !== x;',
+      'foo && foo.bar !== undeclaredVar;',
       'foo && foo.bar != 0;',
       'foo && foo.bar != 1;',
       "foo && foo.bar != '123';",
       'foo && foo.bar != {};',
       'foo && foo.bar != false;',
       'foo && foo.bar != true;',
-      'foo && foo.bar != x;',
-      'foo != null && foo.bar == x;',
+      'foo && foo.bar != undeclaredVar;',
+      'foo != null && foo.bar == undeclaredVar;',
       'foo != null && foo.bar == null;',
       'foo != null && foo.bar == undefined;',
-      'foo != null && foo.bar === x;',
+      'foo != null && foo.bar === undeclaredVar;',
       'foo != null && foo.bar === undefined;',
       'foo != null && foo.bar !== 0;',
       'foo != null && foo.bar !== 1;',
@@ -1379,17 +1379,17 @@ describe('chain ending with comparison', () => {
       'foo != null && foo.bar !== false;',
       'foo != null && foo.bar !== true;',
       'foo != null && foo.bar !== null;',
-      'foo != null && foo.bar !== x;',
+      'foo != null && foo.bar !== undeclaredVar;',
       'foo != null && foo.bar != 0;',
       'foo != null && foo.bar != 1;',
       "foo != null && foo.bar != '123';",
       'foo != null && foo.bar != {};',
       'foo != null && foo.bar != false;',
       'foo != null && foo.bar != true;',
-      'foo != null && foo.bar != x;',
+      'foo != null && foo.bar != undeclaredVar;',
       `
         declare const foo: { bar: number };
-        foo && foo.bar == x;
+        foo && foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1401,7 +1401,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        foo && foo.bar === x;
+        foo && foo.bar === undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1437,7 +1437,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        foo && foo.bar !== x;
+        foo && foo.bar !== undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1465,11 +1465,11 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        foo && foo.bar != x;
+        foo && foo.bar != undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
-        foo != null && foo.bar == x;
+        foo != null && foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1481,7 +1481,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        foo != null && foo.bar === x;
+        foo != null && foo.bar === undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1517,7 +1517,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        foo != null && foo.bar !== x;
+        foo != null && foo.bar !== undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1545,19 +1545,19 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        foo != null && foo.bar != x;
+        foo != null && foo.bar != undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | 1;
-        foo && foo.bar == x;
+        foo && foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | 0;
-        foo != null && foo.bar == x;
+        foo != null && foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
-        foo && foo.bar == x;
+        foo && foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
@@ -1569,7 +1569,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number } | null;
-        foo && foo.bar === x;
+        foo && foo.bar === undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
@@ -1605,11 +1605,11 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number } | null;
-        foo && foo.bar !== x;
+        foo && foo.bar !== undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
-        foo != null && foo.bar == x;
+        foo != null && foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
@@ -1621,7 +1621,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number } | null;
-        foo != null && foo.bar === x;
+        foo != null && foo.bar === undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
@@ -1657,7 +1657,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number } | null;
-        foo != null && foo.bar !== x;
+        foo != null && foo.bar !== undeclaredVar;
       `,
       `
         declare const foo: { bar: number } | null;
@@ -1727,15 +1727,15 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        !foo || foo.bar == x;
+        !foo || foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
-        !foo || foo.bar === x;
+        !foo || foo.bar === undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
-        !foo || foo.bar !== x;
+        !foo || foo.bar !== undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
@@ -1743,7 +1743,7 @@ describe('chain ending with comparison', () => {
       `,
       `
         declare const foo: { bar: number };
-        !foo || foo.bar != x;
+        !foo || foo.bar != undeclaredVar;
       `,
       '!foo && foo.bar == 0;',
       '!foo && foo.bar == 1;',
@@ -1793,7 +1793,7 @@ describe('chain ending with comparison', () => {
         declare const x: 0n | { a: string };
         x && x.a;
       `,
-      '!foo || foo.bar != x;',
+      '!foo || foo.bar != undeclaredVar;',
       '!foo || foo.bar != null;',
       '!foo || foo.bar != undefined;',
       '!foo || foo.bar === 0;',
@@ -1803,29 +1803,29 @@ describe('chain ending with comparison', () => {
       '!foo || foo.bar === false;',
       '!foo || foo.bar === true;',
       '!foo || foo.bar === null;',
-      '!foo || foo.bar === x;',
+      '!foo || foo.bar === undeclaredVar;',
       '!foo || foo.bar == 0;',
       '!foo || foo.bar == 1;',
       "!foo || foo.bar == '123';",
       '!foo || foo.bar == {};',
       '!foo || foo.bar == false;',
       '!foo || foo.bar == true;',
-      '!foo || foo.bar == x;',
-      '!foo || foo.bar !== x;',
+      '!foo || foo.bar == undeclaredVar;',
+      '!foo || foo.bar !== undeclaredVar;',
       '!foo || foo.bar !== undefined;',
       `
         declare const foo: { bar: number };
-        foo == null || foo.bar == x;
+        foo == null || foo.bar == undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
-        foo == null || foo.bar === x;
+        foo == null || foo.bar === undeclaredVar;
       `,
       `
         declare const foo: { bar: number };
-        foo == null || foo.bar !== x;
+        foo == null || foo.bar !== undeclaredVar;
       `,
-      'foo == null || foo.bar != x;',
+      'foo == null || foo.bar != undeclaredVar;',
       'foo == null || foo.bar != null;',
       'foo == null || foo.bar != undefined;',
       'foo == null || foo.bar === 0;',
@@ -1835,15 +1835,15 @@ describe('chain ending with comparison', () => {
       'foo == null || foo.bar === false;',
       'foo == null || foo.bar === true;',
       'foo == null || foo.bar === null;',
-      'foo == null || foo.bar === x;',
+      'foo == null || foo.bar === undeclaredVar;',
       'foo == null || foo.bar == 0;',
       'foo == null || foo.bar == 1;',
       "foo == null || foo.bar == '123';",
       'foo == null || foo.bar == {};',
       'foo == null || foo.bar == false;',
       'foo == null || foo.bar == true;',
-      'foo == null || foo.bar == x;',
-      'foo == null || foo.bar !== x;',
+      'foo == null || foo.bar == undeclaredVar;',
+      'foo == null || foo.bar !== undeclaredVar;',
       'foo == null || foo.bar !== undefined;',
       'foo || foo.bar != 0;',
       'foo || foo.bar != 1;',

From fd98e654f086419e25d823e99745ef952a83a078 Mon Sep 17 00:00:00 2001
From: mdm317 <dbswh1008@gmail.com>
Date: Sat, 18 Oct 2025 02:26:11 +0900
Subject: [PATCH 6/6] fix : weird test csae

---
 .../prefer-optional-chain.test.ts                | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

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
index 946895825cf8..52c59b479b68 100644
--- 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
@@ -1778,20 +1778,20 @@ describe('chain ending with comparison', () => {
       'foo == null && foo.bar != null;',
       'foo == null && foo.bar != undefined;',
       `
-        declare const x: false | { a: string };
-        x && x.a == x;
+        declare const foo: false | { a: string };
+        foo && foo.a == undeclaredVar;
       `,
       `
-        declare const x: '' | { a: string };
-        x && x.a == x;
+        declare const foo: '' | { a: string };
+        foo && foo.a == undeclaredVar;
       `,
       `
-        declare const x: 0 | { a: string };
-        x && x.a == x;
+        declare const foo: 0 | { a: string };
+        foo && foo.a == undeclaredVar;
       `,
       `
-        declare const x: 0n | { a: string };
-        x && x.a;
+        declare const foo: 0n | { a: string };
+        foo && foo.a;
       `,
       '!foo || foo.bar != undeclaredVar;',
       '!foo || foo.bar != null;',