Fix FP 3699 (no-use-of-empty-return-values) to handle ambient functions (#451)

Author: zglicz

scripts/test-ci.sh

@@ -7,7 +7,7 @@ set -euo pipefail
 # variable is set in dockerfile
 if [ "${SONARCLOUD_ANALYSIS:-}" == "true" ]; then
   echo 'Running tests with coverage and reporter'
-  npm run test -- --coverage --testResultsProcessor jest-sonar-reporter
+  npm run test -- --maxWorkers=50% --coverage --testResultsProcessor jest-sonar-reporter
 else
   echo 'Running tests'
   npm run test

src/rules/no-use-of-empty-return-value.ts

@@ -19,35 +19,41 @@
  */
 // https://sonarsource.github.io/rspec/#/rspec/S3699
 
-import type { TSESTree, TSESLint } from '@typescript-eslint/experimental-utils';
+import { TSESTree, TSESLint } from '@typescript-eslint/experimental-utils';
 import { isFunctionExpression, isArrowFunctionExpression, isBlockStatement } from '../utils/nodes';
 import docsUrl from '../utils/docs-url';
 
+const EMPTY_RETURN_VALUE_KEYWORDS = new Set<TSESTree.AST_NODE_TYPES>([
+  TSESTree.AST_NODE_TYPES.TSVoidKeyword,
+  TSESTree.AST_NODE_TYPES.TSNeverKeyword,
+  TSESTree.AST_NODE_TYPES.TSUndefinedKeyword,
+]);
+
 function isReturnValueUsed(callExpr: TSESTree.Node) {
   const { parent } = callExpr;
   if (!parent) {
     return false;
   }
 
-  if (parent.type === 'LogicalExpression') {
+  if (parent.type === TSESTree.AST_NODE_TYPES.LogicalExpression) {
     return parent.left === callExpr;
   }
 
-  if (parent.type === 'SequenceExpression') {
+  if (parent.type === TSESTree.AST_NODE_TYPES.SequenceExpression) {
     return parent.expressions[parent.expressions.length - 1] === callExpr;
   }
 
-  if (parent.type === 'ConditionalExpression') {
+  if (parent.type === TSESTree.AST_NODE_TYPES.ConditionalExpression) {
     return parent.test === callExpr;
   }
 
   return (
-    parent.type !== 'ExpressionStatement' &&
-    parent.type !== 'ArrowFunctionExpression' &&
-    parent.type !== 'UnaryExpression' &&
-    parent.type !== 'AwaitExpression' &&
-    parent.type !== 'ReturnStatement' &&
-    parent.type !== 'ThrowStatement'
+    parent.type !== TSESTree.AST_NODE_TYPES.ExpressionStatement &&
+    parent.type !== TSESTree.AST_NODE_TYPES.ArrowFunctionExpression &&
+    parent.type !== TSESTree.AST_NODE_TYPES.UnaryExpression &&
+    parent.type !== TSESTree.AST_NODE_TYPES.AwaitExpression &&
+    parent.type !== TSESTree.AST_NODE_TYPES.ReturnStatement &&
+    parent.type !== TSESTree.AST_NODE_TYPES.ThrowStatement
   );
 }
 
@@ -102,9 +108,9 @@ const rule: TSESLint.RuleModule<string, string[]> = {
           const ancestors = [...context.getAncestors()].reverse();
           const functionNode = ancestors.find(
             node =>
-              node.type === 'FunctionExpression' ||
-              node.type === 'FunctionDeclaration' ||
-              node.type === 'ArrowFunctionExpression',
+              node.type === TSESTree.AST_NODE_TYPES.FunctionExpression ||
+              node.type === TSESTree.AST_NODE_TYPES.FunctionDeclaration ||
+              node.type === TSESTree.AST_NODE_TYPES.ArrowFunctionExpression,
           );
 
           functionsWithReturnValue.add(functionNode as TSESTree.FunctionLike);
@@ -132,6 +138,16 @@ const rule: TSESLint.RuleModule<string, string[]> = {
         }
       },
 
+      TSDeclareFunction(node: TSESTree.Node) {
+        const declareFunction = node as TSESTree.TSDeclareFunction;
+        if (
+          declareFunction.returnType?.typeAnnotation.type &&
+          !EMPTY_RETURN_VALUE_KEYWORDS.has(declareFunction.returnType?.typeAnnotation.type)
+        ) {
+          functionsWithReturnValue.add(declareFunction);
+        }
+      },
+
       'Program:exit'() {
         callExpressionsToCheck.forEach((functionDeclaration, callee) => {
           if (!functionsWithReturnValue.has(functionDeclaration)) {

tests/rules/no-use-of-empty-return-value.test.ts

@@ -51,6 +51,7 @@ ruleTester.run('no-use-of-empty-return-value', rule, {
     },
     { code: 'function* noReturn() { yield 1; } noReturn().next();' },
     { code: 'function* noReturn() { yield 1; } noReturn();' },
+    { code: 'declare function withReturn(): number; let x = withReturn();' },
   ],
   invalid: [
     invalidPrefixWithFunction('console.log(noReturn());'),
@@ -69,6 +70,9 @@ ruleTester.run('no-use-of-empty-return-value', rule, {
     ),
     invalid('var funcExpr = function noReturn () { 1; console.log(noReturn()); };'),
     invalid('var noReturn = () => { var x = () => {return 1}  }; x = noReturn();'),
+    invalid('declare function noReturn(): never; let x = noReturn();'),
+    invalid('declare function noReturn(): void; let x = noReturn();'),
+    invalid('declare function noReturn(): undefined; let x = noReturn();'),
   ],
 });