Fix FP S6606 (prefer-nullish-coalescing): When the first argument s boolean | undefined

packages/jsts/src/rules/S6606/fixtures/index.ts

@@ -0,0 +1 @@
+// intentionally left empty

packages/jsts/src/rules/S6606/fixtures/tsconfig.json

@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "strictNullChecks": true
+  }
+}

packages/jsts/src/rules/S6606/index.ts

@@ -0,0 +1,20 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+export * from './rule';

packages/jsts/src/rules/S6606/rule.ts

@@ -0,0 +1,55 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+import { tsEslintRules } from '../typescript-eslint';
+import { type Rule } from 'eslint';
+import {
+  getTypeFromTreeNode,
+  interceptReport,
+  isNullOrUndefinedType,
+  isObjectType,
+  isPrimitiveType,
+} from '../helpers';
+import { LogicalExpression } from 'estree';
+
+const preferNullishCoalescingRule = tsEslintRules['prefer-nullish-coalescing'];
+
+export const rule = interceptReport(preferNullishCoalescingRule, (context, reportDescriptor) => {
+  const { node: token, messageId } = reportDescriptor as Rule.ReportDescriptor & {
+    node: Rule.Node;
+    messageId: string;
+  };
+
+  if (messageId === 'preferNullishOverOr') {
+    const services = context.sourceCode.parserServices;
+    const node = context.sourceCode.getNodeByRangeIndex(token.range![0]) as LogicalExpression;
+    const leftOperand = node.left;
+    const leftOperandType = getTypeFromTreeNode(leftOperand, services);
+
+    if (
+      leftOperandType.isUnion() &&
+      leftOperandType.types.some(isNullOrUndefinedType) &&
+      (leftOperandType.types.some(isPrimitiveType) || leftOperandType.types.some(isObjectType))
+    ) {
+      return;
+    }
+  }
+
+  context.report(reportDescriptor);
+});

packages/jsts/src/rules/S6606/unit.test.ts

@@ -0,0 +1,102 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+import { rule } from './rule';
+import { RuleTester } from 'eslint';
+import path from 'path';
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('@typescript-eslint/parser'),
+  parserOptions: {
+    ecmaVersion: 2018,
+    sourceType: 'module',
+    project: `./tsconfig.json`,
+    tsconfigRootDir: path.join(__dirname, 'fixtures'),
+  },
+});
+
+ruleTester.run('S6606', rule, {
+  valid: [
+    {
+      code: `
+  function foo(value: string) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: string | number) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: string | null) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: number | null) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: bigint | null) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: boolean | null) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: { baz: number } | null) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+    {
+      code: `
+  function foo(value: Date | null) {
+    return value || 'default';
+  }
+  `,
+      filename: path.join(__dirname, 'fixtures/index.ts'),
+    },
+  ],
+  invalid: [],
+});

packages/jsts/src/rules/helpers/type.ts

@@ -291,3 +291,21 @@ export function isBooleanLiteralType(type: ts.Type): type is ts.Type & {
 export function isBooleanTrueType(type: ts.Type) {
   return isBooleanLiteralType(type) && type.intrinsicName === 'true';
 }
+
+export function isPrimitiveType({ flags }: ts.Type) {
+  return (
+    flags & ts.TypeFlags.BooleanLike ||
+    flags & ts.TypeFlags.BigIntLike ||
+    flags & ts.TypeFlags.NumberLike ||
+    flags & ts.TypeFlags.StringLike ||
+    flags & ts.TypeFlags.EnumLike
+  );
+}
+
+export function isNullOrUndefinedType({ flags }: ts.Type) {
+  return flags & ts.TypeFlags.Null || flags & ts.TypeFlags.Undefined;
+}
+
+export function isObjectType({ flags }: ts.Type) {
+  return flags & ts.TypeFlags.Object;
+}