fix(no-floating-observables): handle chain expressions

Author: JasonWeinzierl

src/etc/is.ts

@@ -34,6 +34,10 @@ export function isCallExpression(node: TSESTree.Node): node is TSESTree.CallExpr
   return node.type === AST_NODE_TYPES.CallExpression;
 }
 
+export function isChainExpression(node: TSESTree.Node): node is TSESTree.ChainExpression {
+  return node.type === AST_NODE_TYPES.ChainExpression;
+}
+
 export function isExportNamedDeclaration(
   node: TSESTree.Node,
 ): node is TSESTree.ExportNamedDeclaration {

src/rules/no-floating-observables.ts

@@ -1,5 +1,5 @@
 import { TSESTree as es } from '@typescript-eslint/utils';
-import { getTypeServices, isCallExpression } from '../etc';
+import { getTypeServices, isCallExpression, isChainExpression } from '../etc';
 import { ruleCreator } from '../utils';
 
 const defaultOptions: readonly {
@@ -57,9 +57,19 @@ export const noFloatingObservablesRule = ruleCreator({
       'ExpressionStatement > UnaryExpression': (node: es.UnaryExpression) => {
         if (ignoreVoid) return;
         if (node.operator !== 'void') return;
-        if (!isCallExpression(node.argument)) return;
 
-        checkNode(node.argument);
+        let expression = node.argument;
+        if (isChainExpression(expression)) {
+          expression = expression.expression;
+        }
+
+        if (!isCallExpression(expression)) return;
+        checkNode(expression);
+      },
+      'ExpressionStatement > ChainExpression': (node: es.ChainExpression) => {
+        if (!isCallExpression(node.expression)) return;
+
+        checkNode(node.expression);
       },
     };
   },

tests/rules/no-floating-observables.test.ts

@@ -61,6 +61,17 @@ ruleTester({ types: true }).run('no-floating-observables', noFloatingObservables
         ~~~~~~~~~~~~~ [forbidden]
       `,
     ),
+    fromFixture(
+      stripIndent`
+        // chain expression
+        import { Observable, of } from "rxjs";
+
+        const arrowSource: null | (() => Observable<number>) = () => of(42);
+
+        arrowSource?.();
+        ~~~~~~~~~~~~~~~ [forbidden]
+      `,
+    ),
     fromFixture(
       stripIndent`
         // ignoreVoid false
@@ -72,6 +83,8 @@ ruleTester({ types: true }).run('no-floating-observables', noFloatingObservables
 
         void functionSource();
              ~~~~~~~~~~~~~~~~ [forbiddenNoVoid]
+        void functionSource?.();
+             ~~~~~~~~~~~~~~~~~~ [forbiddenNoVoid]
       `,
       {
         options: [{ ignoreVoid: false }],