fix(eslint-plugin): [require-await] Allow concise arrow function bodies (typescript-eslint#826)

scottohara · bradzacher · commit 29fddfd14959 · 2019-08-21T09:48:44.000-07:00
diff --git a/packages/eslint-plugin/src/rules/require-await.ts b/packages/eslint-plugin/src/rules/require-await.ts
@@ -64,6 +64,15 @@ export default util.createRule<Options, MessageIds>({
 
         case AST_NODE_TYPES.ArrowFunctionExpression:
           rules.ArrowFunctionExpression(node);
+
+          // If body type is not BlockStatment, we need to check the return type here
+          if (node.body.type !== AST_NODE_TYPES.BlockStatement) {
+            const expression = parserServices.esTreeNodeToTSNodeMap.get(
+              node.body,
+            );
+            scopeInfo.returnsPromise = isThenableType(expression);
+          }
+
           break;
       }
     }
@@ -102,6 +111,18 @@ export default util.createRule<Options, MessageIds>({
       }
     }
 
+    /**
+     * Checks if the node returns a thenable type
+     *
+     * @param {ASTNode} node - The node to check
+     * @returns {boolean}
+     */
+    function isThenableType(node: ts.Node) {
+      const type = checker.getTypeAtLocation(node);
+
+      return tsutils.isThenableType(checker, node, type);
+    }
+
     return {
       'FunctionDeclaration[async = true]': enterFunction,
       'FunctionExpression[async = true]': enterFunction,
@@ -122,10 +143,7 @@ export default util.createRule<Options, MessageIds>({
           return;
         }
 
-        const type = checker.getTypeAtLocation(expression);
-        if (tsutils.isThenableType(checker, expression, type)) {
-          scopeInfo.returnsPromise = true;
-        }
+        scopeInfo.returnsPromise = isThenableType(expression);
       },
 
       AwaitExpression: rules.AwaitExpression as TSESLint.RuleFunction<
diff --git a/packages/eslint-plugin/tests/rules/require-await.test.ts b/packages/eslint-plugin/tests/rules/require-await.test.ts
@@ -41,9 +41,15 @@ ruleTester.run('require-await', rule, {
       }`,
     },
     {
-      // Non-async arrow function expression
+      // Non-async arrow function expression (concise-body)
       code: `const numberOne = (): number => 1;`,
     },
+    {
+      // Non-async arrow function expression (block-body)
+      code: `const numberOne = (): number => {
+        return 1;
+      };`,
+    },
     {
       // Async function declaration with await
       code: `async function numberOne(): Promise<number> {
@@ -57,9 +63,15 @@ ruleTester.run('require-await', rule, {
       }`,
     },
     {
-      // Async arrow function expression with await
+      // Async arrow function expression with await (concise-body)
       code: `const numberOne = async (): Promise<number> => await 1;`,
     },
+    {
+      // Async arrow function expression with await (block-body)
+      code: `const numberOne = async (): Promise<number> => {
+        return await 1;
+      };`,
+    },
     {
       // Async function declaration with promise return
       code: `async function numberOne(): Promise<number> {
@@ -72,6 +84,16 @@ ruleTester.run('require-await', rule, {
         return Promise.resolve(1);
       }`,
     },
+    {
+      // Async arrow function with promise return (concise-body)
+      code: `const numberOne = async (): Promise<number> => Promise.resolve(1);`,
+    },
+    {
+      // Async arrow function with promise return (block-body)
+      code: `const numberOne = async (): Promise<number> => {
+        return Promise.resolve(1);
+      };`,
+    },
     {
       // Async function declaration with async function return
       code: `async function numberOne(): Promise<number> {
@@ -90,6 +112,22 @@ ruleTester.run('require-await', rule, {
         return Promise.resolve(x);
       }`,
     },
+    {
+      // Async arrow function with async function return (concise-body)
+      code: `const numberOne = async (): Promise<number> => getAsyncNumber(1);
+      const getAsyncNumber = async function(x: number): Promise<number> {
+        return Promise.resolve(x);
+      }`,
+    },
+    {
+      // Async arrow function with async function return (block-body)
+      code: `const numberOne = async (): Promise<number> => {
+        return getAsyncNumber(1);
+      };
+      const getAsyncNumber = async function(x: number): Promise<number> {
+        return Promise.resolve(x);
+      }`,
+    },
   ],
 
   invalid: [
