fix(eslint-plugin): [prefer-optional-chain] properly disambiguate bet…

…ween `boolean` and `false` (#8685) * make the example from the docs work * revert * allow falsey literals on last operand
typescript-eslint · Mar 25, 2024 · 2018f91 · 2018f91
1 parent 56358a6
commit 2018f91
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Showing 2 changed files with 23 additions and 9 deletions.
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
@@ -61,17 +61,13 @@ type Operand = ValidOperand | InvalidOperand;
 const NULLISH_FLAGS = ts.TypeFlags.Null | ts.TypeFlags.Undefined;
 function isValidFalseBooleanCheckType(
   node: TSESTree.Node,
-  operator: TSESTree.LogicalExpression['operator'],
-  checkType: 'true' | 'false',
+  disallowFalseyLiteral: boolean,
   parserServices: ParserServicesWithTypeInformation,
   options: PreferOptionalChainOptions,
 ): boolean {
   const type = parserServices.getTypeAtLocation(node);
   const types = unionTypeParts(type);
 
-  const disallowFalseyLiteral =
-    (operator === '||' && checkType === 'false') ||
-    (operator === '&&' && checkType === 'true');
   if (disallowFalseyLiteral) {
     /*
     ```
@@ -133,6 +129,7 @@ export function gatherLogicalOperands(
   const { operands, newlySeenLogicals } = flattenLogicalOperands(node);
 
   for (const operand of operands) {
+    const areMoreOperands = operand !== operands.at(-1);
     switch (operand.type) {
       case AST_NODE_TYPES.BinaryExpression: {
         // check for "yoda" style logical: null != x
@@ -258,8 +255,7 @@ export function gatherLogicalOperands(
           operand.operator === '!' &&
           isValidFalseBooleanCheckType(
             operand.argument,
-            node.operator,
-            'false',
+            areMoreOperands && node.operator === '||',
             parserServices,
             options,
           )
@@ -285,8 +281,7 @@ export function gatherLogicalOperands(
         if (
           isValidFalseBooleanCheckType(
             operand,
-            node.operator,
-            'true',
+            areMoreOperands && node.operator === '&&',
             parserServices,
             options,
           )

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
@@ -1945,6 +1945,25 @@ describe('hand-crafted cases', () => {
           },
         ],
       },
+      {
+        code: `
+          declare const foo: { bar: boolean } | null | undefined;
+          declare function acceptsBoolean(arg: boolean): void;
+          acceptsBoolean(foo != null && foo.bar);
+        `,
+        output: `
+          declare const foo: { bar: boolean } | null | undefined;
+          declare function acceptsBoolean(arg: boolean): void;
+          acceptsBoolean(foo?.bar);
+        `,
+        options: [
+          {
+            allowPotentiallyUnsafeFixesThatModifyTheReturnTypeIKnowWhatImDoing:
+              true,
+          },
+        ],
+        errors: [{ messageId: 'preferOptionalChain' }],
+      },
       {
         code: `
           function foo(globalThis?: { Array: Function }) {