fix(eslint-plugin): [strict-boolean-expression] support falsy and truthy literals simultaneously (#6672)

* support falsy and truthy literals simultanously

* replace Array.prototype.some condition with Array.prototype.every

* format test cases to match prettier configuration

---------

Co-authored-by: Michał Kozłowski <michal.kozlowski@start-up.house>

Author: kozlovvski

packages/eslint-plugin/src/rules/strict-boolean-expressions.ts

@@ -835,7 +835,9 @@ export default util.createRule<Options, MessageId>({
       );
 
       if (strings.length) {
-        if (strings.some(type => type.isStringLiteral() && type.value !== '')) {
+        if (
+          strings.every(type => type.isStringLiteral() && type.value !== '')
+        ) {
           variantTypes.add('truthy string');
         } else {
           variantTypes.add('string');
@@ -848,8 +850,9 @@ export default util.createRule<Options, MessageId>({
           ts.TypeFlags.NumberLike | ts.TypeFlags.BigIntLike,
         ),
       );
+
       if (numbers.length) {
-        if (numbers.some(type => type.isNumberLiteral() && type.value !== 0)) {
+        if (numbers.every(type => type.isNumberLiteral() && type.value !== 0)) {
           variantTypes.add('truthy number');
         } else {
           variantTypes.add('number');

packages/eslint-plugin/tests/rules/strict-boolean-expressions.test.ts

@@ -894,6 +894,7 @@ if (y) {
         declare const x: string | null; if (x) {}
         (x?: string) => !x;
         <T extends string | null | undefined>(x: T) => x ? 1 : 0;
+        function foo(x: '' | 'bar' | null) { if (!x) {} }
       `,
       errors: [
         {
@@ -956,6 +957,28 @@ if (y) {
             },
           ],
         },
+        {
+          messageId: 'conditionErrorNullableString',
+          line: 5,
+          column: 51,
+          suggestions: [
+            {
+              messageId: 'conditionFixCompareNullish',
+              output:
+                "        function foo(x: '' | 'bar' | null) { if (x == null) {} }",
+            },
+            {
+              messageId: 'conditionFixDefaultEmptyString',
+              output:
+                "        function foo(x: '' | 'bar' | null) { if (!(x ?? \"\")) {} }",
+            },
+            {
+              messageId: 'conditionFixCastBoolean',
+              output:
+                "        function foo(x: '' | 'bar' | null) { if (!Boolean(x)) {} }",
+            },
+          ],
+        },
       ],
     }),
 
@@ -965,6 +988,7 @@ if (y) {
         declare const x: number | null; if (x) {}
         (x?: number) => !x;
         <T extends number | null | undefined>(x: T) => x ? 1 : 0;
+        function foo(x: 0 | 1 | null) { if (!x) {} }
       `,
       errors: [
         {
@@ -1027,6 +1051,28 @@ if (y) {
             },
           ],
         },
+        {
+          messageId: 'conditionErrorNullableNumber',
+          line: 5,
+          column: 46,
+          suggestions: [
+            {
+              messageId: 'conditionFixCompareNullish',
+              output:
+                '        function foo(x: 0 | 1 | null) { if (x == null) {} }',
+            },
+            {
+              messageId: 'conditionFixDefaultZero',
+              output:
+                '        function foo(x: 0 | 1 | null) { if (!(x ?? 0)) {} }',
+            },
+            {
+              messageId: 'conditionFixCastBoolean',
+              output:
+                '        function foo(x: 0 | 1 | null) { if (!Boolean(x)) {} }',
+            },
+          ],
+        },
       ],
     }),