no-useless-undefined: Forbid undefined as right side of ?? expression (#2799)

Author: fisker

rules/no-useless-undefined.js

@@ -216,6 +216,31 @@ const create = context => {
 		}
 	});
 
+	// `foo ?? undefined`
+	context.on('Identifier', node => {
+		if (
+			isUndefined(node)
+			&& node.parent.type === 'LogicalExpression'
+			&& node.parent.operator === '??'
+			&& node.parent.right === node
+		) {
+			return getProblem(
+				node,
+				fixer => {
+					const logicalExpression = node.parent;
+					const operatorToken = sourceCode.getTokenBefore(node, token => token.value === logicalExpression.operator);
+					const tokenBeforeOperatorToken = sourceCode.getTokenBefore(operatorToken);
+
+					return fixer.removeRange([
+						sourceCode.getRange(tokenBeforeOperatorToken)[1],
+						sourceCode.getRange(logicalExpression)[1],
+					]);
+				},
+				/* CheckFunctionReturnType */ false,
+			);
+		}
+	});
+
 	if (!options.checkArguments) {
 		return;
 	}

test/no-useless-undefined.js

@@ -497,3 +497,19 @@ test.snapshot({
 		},
 	],
 });
+
+// `foo ?? undefined`
+test.snapshot({
+	valid: [
+		'foo || undefined',
+		'foo && undefined',
+		'foo ?? null',
+		'undefined ?? foo',
+	],
+	invalid: [
+		'foo ?? undefined',
+		'(( (( foo )) ?? (( undefined )) ))',
+		'foo ?? null ?? undefined',
+		'call(foo ?? undefined,)',
+	],
+});

test/snapshots/no-useless-undefined.js.md

@@ -790,3 +790,87 @@ Generated by [AVA](https://avajs.dev).
     > 1 | function a({foo} = undefined) {}␊
         |                    ^^^^^^^^^ Do not use useless \`undefined\`.␊
     `
+
+## invalid(1): foo ?? undefined
+
+> Input
+
+    `␊
+      1 | foo ?? undefined␊
+    `
+
+> Output
+
+    `␊
+      1 | foo␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | foo ?? undefined␊
+        |        ^^^^^^^^^ Do not use useless \`undefined\`.␊
+    `
+
+## invalid(2): (( (( foo )) ?? (( undefined )) ))
+
+> Input
+
+    `␊
+      1 | (( (( foo )) ?? (( undefined )) ))␊
+    `
+
+> Output
+
+    `␊
+      1 | (( (( foo )) ))␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | (( (( foo )) ?? (( undefined )) ))␊
+        |                    ^^^^^^^^^ Do not use useless \`undefined\`.␊
+    `
+
+## invalid(3): foo ?? null ?? undefined
+
+> Input
+
+    `␊
+      1 | foo ?? null ?? undefined␊
+    `
+
+> Output
+
+    `␊
+      1 | foo ?? null␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | foo ?? null ?? undefined␊
+        |                ^^^^^^^^^ Do not use useless \`undefined\`.␊
+    `
+
+## invalid(4): call(foo ?? undefined,)
+
+> Input
+
+    `␊
+      1 | call(foo ?? undefined,)␊
+    `
+
+> Output
+
+    `␊
+      1 | call(foo,)␊
+    `
+
+> Error 1/1
+
+    `␊
+    > 1 | call(foo ?? undefined,)␊
+        |             ^^^^^^^^^ Do not use useless \`undefined\`.␊
+    `