Only provide suggestion for outermost async fix

src/services/codefixes/convertToAsyncFunction.ts

@@ -60,7 +60,7 @@ namespace ts.codefix {
         const setOfExpressionsToReturn = getAllPromiseExpressionsToReturn(functionToConvert, checker);
         const functionToConvertRenamed = renameCollidingVarNames(functionToConvert, checker, synthNamesMap, context, setOfExpressionsToReturn, originalTypeMap, allVarNames);
         const constIdentifiers = getConstIdentifiers(synthNamesMap);
-        const returnStatements = functionToConvertRenamed.body && isBlock(functionToConvertRenamed.body) ? getReturnStatementsWithPromiseHandlers(functionToConvertRenamed.body) : emptyArray;
+        const returnStatements = functionToConvertRenamed.body && isBlock(functionToConvertRenamed.body) ? getReturnStatementsWithPromiseHandlers(functionToConvertRenamed.body, checker) : emptyArray;
         const transformer: Transformer = { checker, synthNamesMap, allVarNames, setOfExpressionsToReturn, constIdentifiers, originalTypeMap, isInJSFile: isInJavascript };
 
         if (!returnStatements.length) {
@@ -87,10 +87,10 @@ namespace ts.codefix {
         }
     }
 
-    function getReturnStatementsWithPromiseHandlers(body: Block): ReadonlyArray<ReturnStatement> {
+    function getReturnStatementsWithPromiseHandlers(body: Block, checker: TypeChecker): ReadonlyArray<ReturnStatement> {
         const res: ReturnStatement[] = [];
         forEachReturnStatement(body, ret => {
-            if (isReturnStatementWithFixablePromiseHandler(ret)) res.push(ret);
+            if (isReturnStatementWithFixablePromiseHandler(ret, checker)) res.push(ret);
         });
         return res;
     }
@@ -450,7 +450,7 @@ namespace ts.codefix {
                             seenReturnStatement = true;
                         }
 
-                        if (isReturnStatementWithFixablePromiseHandler(statement)) {
+                        if (isReturnStatementWithFixablePromiseHandler(statement, transformer.checker)) {
                             refactoredStmts = refactoredStmts.concat(getInnerTransformationBody(transformer, [statement], prevArgName));
                         }
                         else {
@@ -466,7 +466,7 @@ namespace ts.codefix {
                             seenReturnStatement);
                 }
                 else {
-                    const innerRetStmts = isFixablePromiseHandler(funcBody) ? [createReturn(funcBody)] : emptyArray;
+                    const innerRetStmts = isFixablePromiseHandler(funcBody, transformer.checker) ? [createReturn(funcBody)] : emptyArray;
                     const innerCbBody = getInnerTransformationBody(transformer, innerRetStmts, prevArgName);
 
                     if (innerCbBody.length > 0) {

src/services/suggestionDiagnostics.ts

@@ -1,5 +1,7 @@
 /* @internal */
 namespace ts {
+    const visitedNestedConvertibleFunctions = createMap<true>();
+
     export function computeSuggestionDiagnostics(sourceFile: SourceFile, program: Program, cancellationToken: CancellationToken): DiagnosticWithLocation[] {
         program.getSemanticDiagnostics(sourceFile, cancellationToken);
         const diags: DiagnosticWithLocation[] = [];
@@ -13,6 +15,7 @@ namespace ts {
 
         const isJsFile = isSourceFileJS(sourceFile);
 
+        visitedNestedConvertibleFunctions.clear();
         check(sourceFile);
 
         if (getAllowSyntheticDefaultImports(program.getCompilerOptions())) {
@@ -114,17 +117,21 @@ namespace ts {
     }
 
     function addConvertToAsyncFunctionDiagnostics(node: FunctionLikeDeclaration, checker: TypeChecker, diags: Push<DiagnosticWithLocation>): void {
-        if (!isAsyncFunction(node) &&
-            node.body &&
-            isBlock(node.body) &&
-            hasReturnStatementWithPromiseHandler(node.body) &&
-            returnsPromise(node, checker)) {
+        if (!visitedNestedConvertibleFunctions.has(getKeyFromNode(node)) && isConvertableFunction(node, checker)) {
             diags.push(createDiagnosticForNode(
                 !node.name && isVariableDeclaration(node.parent) && isIdentifier(node.parent.name) ? node.parent.name : node,
                 Diagnostics.This_may_be_converted_to_an_async_function));
         }
     }
 
+    function isConvertableFunction(node: FunctionLikeDeclaration, checker: TypeChecker) {
+        return !isAsyncFunction(node) &&
+            node.body &&
+            isBlock(node.body) &&
+            hasReturnStatementWithPromiseHandler(node.body, checker) &&
+            returnsPromise(node, checker);
+    }
+
     function returnsPromise(node: FunctionLikeDeclaration, checker: TypeChecker): boolean {
         const functionType = checker.getTypeAtLocation(node);
         const callSignatures = checker.getSignaturesOfType(functionType, SignatureKind.Call);
@@ -136,25 +143,25 @@ namespace ts {
         return isBinaryExpression(commonJsModuleIndicator) ? commonJsModuleIndicator.left : commonJsModuleIndicator;
     }
 
-    function hasReturnStatementWithPromiseHandler(body: Block): boolean {
-        return !!forEachReturnStatement(body, isReturnStatementWithFixablePromiseHandler);
+    function hasReturnStatementWithPromiseHandler(body: Block, checker: TypeChecker): boolean {
+        return !!forEachReturnStatement(body, stmt => isReturnStatementWithFixablePromiseHandler(stmt, checker));
     }
 
-    export function isReturnStatementWithFixablePromiseHandler(node: Node): node is ReturnStatement {
-        return isReturnStatement(node) && !!node.expression && isFixablePromiseHandler(node.expression);
+    export function isReturnStatementWithFixablePromiseHandler(node: Node, checker: TypeChecker): node is ReturnStatement {
+        return isReturnStatement(node) && !!node.expression && isFixablePromiseHandler(node.expression, checker);
     }
 
     // Should be kept up to date with transformExpression in convertToAsyncFunction.ts
-    export function isFixablePromiseHandler(node: Node): boolean {
+    export function isFixablePromiseHandler(node: Node, checker: TypeChecker): boolean {
         // ensure outermost call exists and is a promise handler
-        if (!isPromiseHandler(node) || !node.arguments.every(isFixablePromiseArgument)) {
+        if (!isPromiseHandler(node) || !node.arguments.every((arg) => isFixablePromiseArgument(arg, checker))) {
             return false;
         }
 
         // ensure all chained calls are valid
         let currentNode = node.expression;
         while (isPromiseHandler(currentNode) || isPropertyAccessExpression(currentNode)) {
-            if (isCallExpression(currentNode) && !currentNode.arguments.every(isFixablePromiseArgument)) {
+            if (isCallExpression(currentNode) && !currentNode.arguments.every(arg => isFixablePromiseArgument(arg, checker))) {
                 return false;
             }
             currentNode = currentNode.expression;
@@ -167,16 +174,24 @@ namespace ts {
     }
 
     // should be kept up to date with getTransformationBody in convertToAsyncFunction.ts
-    function isFixablePromiseArgument(arg: Expression): boolean {
+    function isFixablePromiseArgument(arg: Expression, checker: TypeChecker): boolean {
         switch (arg.kind) {
-            case SyntaxKind.NullKeyword:
-            case SyntaxKind.Identifier: // identifier includes undefined
             case SyntaxKind.FunctionDeclaration:
             case SyntaxKind.FunctionExpression:
             case SyntaxKind.ArrowFunction:
+                if (isConvertableFunction(arg as FunctionLikeDeclaration, checker)) {
+                    visitedNestedConvertibleFunctions.set(getKeyFromNode(arg as FunctionLikeDeclaration), true);
+                }
+                /* falls through */
+            case SyntaxKind.NullKeyword:
+            case SyntaxKind.Identifier: // identifier includes undefined
                 return true;
             default:
                 return false;
         }
     }
+
+    function getKeyFromNode(exp: FunctionLikeDeclaration) {
+        return `${exp.pos.toString()}:${exp.end.toString()}`;
+    }
 }

src/testRunner/unittests/services/convertToAsyncFunction.ts

@@ -255,7 +255,7 @@ interface String { charAt: any; }
 interface Array<T> {}`
     };
 
-    function testConvertToAsyncFunction(caption: string, text: string, baselineFolder: string, includeLib?: boolean, expectFailure = false) {
+    function testConvertToAsyncFunction(caption: string, text: string, baselineFolder: string, includeLib?: boolean, expectFailure = false, onlyProvideAction = false) {
         const t = extractTest(text);
         const selectionRange = t.ranges.get("selection")!;
         if (!selectionRange) {
@@ -307,7 +307,7 @@ interface Array<T> {}`
 
             const actions = codefix.getFixes(context);
             const action = find(actions, action => action.description === Diagnostics.Convert_to_async_function.message);
-            if (expectFailure) {
+            if (expectFailure && !onlyProvideAction) {
                 assert.isNotTrue(action && action.changes.length > 0);
                 return;
             }
@@ -1151,25 +1151,25 @@ function [#|f|]() {
     _testConvertToAsyncFunction("convertToAsyncFunction_simpleFunctionExpression", `
 const [#|foo|] = function () {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 `);
 
     _testConvertToAsyncFunction("convertToAsyncFunction_simpleFunctionExpressionWithName", `
 const foo = function [#|f|]() {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 `);
 
     _testConvertToAsyncFunction("convertToAsyncFunction_simpleFunctionExpressionAssignedToBindingPattern", `
 const { length } = [#|function|] () {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 `);
 
     _testConvertToAsyncFunction("convertToAsyncFunction_catchBlockUniqueParams", `
 function [#|f|]() {
-	return Promise.resolve().then(x => 1).catch(x => "a").then(x => !!x); 
-} 
+	return Promise.resolve().then(x => 1).catch(x => "a").then(x => !!x);
+}
 `);
 
     _testConvertToAsyncFunction("convertToAsyncFunction_bindingPattern", `
@@ -1178,7 +1178,7 @@ function [#|f|]() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}
 `);
 
     _testConvertToAsyncFunction("convertToAsyncFunction_bindingPatternNameCollision", `
@@ -1188,7 +1188,7 @@ function [#|f|]() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}
 `);
 
     _testConvertToAsyncFunctionFailed("convertToAsyncFunction_thenArgumentNotFunction", `
@@ -1209,7 +1209,7 @@ function [#|f|]() {
 }
 function res(result) {
     return Promise.resolve().then(x => console.log(result));
-} 
+}
 `);
 
     _testConvertToAsyncFunction("convertToAsyncFunction_callbackReturnsPromise", `
@@ -1241,7 +1241,7 @@ function [#|f|]() {
     return Promise.resolve(1)
         .then(x => Promise.reject(x))
         .catch(err => console.log(err));
-}    
+}
 `);
 
 _testConvertToAsyncFunction("convertToAsyncFunction_nestedPromises", `
@@ -1266,6 +1266,22 @@ _testConvertToAsyncFunction("convertToAsyncFunction_exportModifier", `
 export function [#|foo|]() {
     return fetch('https://typescriptlang.org').then(s => console.log(s));
 }
+`);
+
+_testConvertToAsyncFunction("convertToAsyncFunction_OutermostOnlySuccess", `
+function [#|foo|]() {
+    return fetch('a').then(() => {
+        return fetch('b').then(() => 'c');
+    })
+}
+`);
+
+_testConvertToAsyncFunctionFailedSuggestion("convertToAsyncFunction_OutermostOnlyFailure", `
+function foo() {
+    return fetch('a').then([#|() => {|]
+        return fetch('b').then(() => 'c');
+    })
+}
 `);
     });
 
@@ -1276,4 +1292,8 @@ export function [#|foo|]() {
     function _testConvertToAsyncFunctionFailed(caption: string, text: string) {
         testConvertToAsyncFunction(caption, text, "convertToAsyncFunction", /*includeLib*/ true, /*expectFailure*/ true);
     }
+
+    function _testConvertToAsyncFunctionFailedSuggestion(caption: string, text: string) {
+        testConvertToAsyncFunction(caption, text, "convertToAsyncFunction", /*includeLib*/ true, /*expectFailure*/ true, /*onlyProvideAction*/ true);
+    }
 }

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_OutermostOnlyFailure.ts

@@ -0,0 +1,16 @@
+// ==ORIGINAL==
+
+function foo() {
+    return fetch('a').then(/*[#|*/() => {/*|]*/
+        return fetch('b').then(() => 'c');
+    })
+}
+
+// ==ASYNC FUNCTION::Convert to async function==
+
+function foo() {
+    return fetch('a').then(async () => {
+        await fetch('b');
+        return 'c';
+    })
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_OutermostOnlySuccess.js

@@ -0,0 +1,15 @@
+// ==ORIGINAL==
+
+function /*[#|*/foo/*|]*/() {
+    return fetch('a').then(() => {
+        return fetch('b').then(() => 'c');
+    })
+}
+
+// ==ASYNC FUNCTION::Convert to async function==
+
+async function foo() {
+    await fetch('a');
+    await fetch('b');
+    return 'c';
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_OutermostOnlySuccess.ts

@@ -0,0 +1,15 @@
+// ==ORIGINAL==
+
+function /*[#|*/foo/*|]*/() {
+    return fetch('a').then(() => {
+        return fetch('b').then(() => 'c');
+    })
+}
+
+// ==ASYNC FUNCTION::Convert to async function==
+
+async function foo() {
+    await fetch('a');
+    await fetch('b');
+    return 'c';
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_bindingPattern.js

@@ -5,7 +5,7 @@ function /*[#|*/f/*|]*/() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -15,4 +15,4 @@ async function f() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_bindingPattern.ts

@@ -5,7 +5,7 @@ function /*[#|*/f/*|]*/() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -15,4 +15,4 @@ async function f() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_bindingPatternNameCollision.js

@@ -6,7 +6,7 @@ function /*[#|*/f/*|]*/() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -17,4 +17,4 @@ async function f() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_bindingPatternNameCollision.ts

@@ -6,7 +6,7 @@ function /*[#|*/f/*|]*/() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -17,4 +17,4 @@ async function f() {
 }
 function res({ status, trailer }){
     console.log(status);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_callbackReturnsRejectedPromiseInTryBlock.js

@@ -4,7 +4,7 @@ function /*[#|*/f/*|]*/() {
     return Promise.resolve(1)
         .then(x => Promise.reject(x))
         .catch(err => console.log(err));
-}    
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -16,4 +16,4 @@ async function f() {
     catch (err) {
         return console.log(err);
     }
-}    
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_callbackReturnsRejectedPromiseInTryBlock.ts

@@ -4,7 +4,7 @@ function /*[#|*/f/*|]*/() {
     return Promise.resolve(1)
         .then(x => Promise.reject(x))
         .catch(err => console.log(err));
-}    
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -16,4 +16,4 @@ async function f() {
     catch (err) {
         return console.log(err);
     }
-}    
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_catchBlockUniqueParams.js

@@ -1,8 +1,8 @@
 // ==ORIGINAL==
 
 function /*[#|*/f/*|]*/() {
-	return Promise.resolve().then(x => 1).catch(x => "a").then(x => !!x); 
-} 
+	return Promise.resolve().then(x => 1).catch(x => "a").then(x => !!x);
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -15,5 +15,5 @@ async function f() {
     catch (x_1) {
         x_2 = "a";
     }
-    return !!x_2; 
-} 
+    return !!x_2;
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_catchBlockUniqueParams.ts

@@ -1,8 +1,8 @@
 // ==ORIGINAL==
 
 function /*[#|*/f/*|]*/() {
-	return Promise.resolve().then(x => 1).catch(x => "a").then(x => !!x); 
-} 
+	return Promise.resolve().then(x => 1).catch(x => "a").then(x => !!x);
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -15,5 +15,5 @@ async function f() {
     catch (x_1) {
         x_2 = "a";
     }
-    return !!x_2; 
-} 
+    return !!x_2;
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_runEffectfulContinuation.js

@@ -5,7 +5,7 @@ function /*[#|*/f/*|]*/() {
 }
 function res(result) {
     return Promise.resolve().then(x => console.log(result));
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -16,4 +16,4 @@ async function f() {
 }
 function res(result) {
     return Promise.resolve().then(x => console.log(result));
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_runEffectfulContinuation.ts

@@ -5,7 +5,7 @@ function /*[#|*/f/*|]*/() {
 }
 function res(result) {
     return Promise.resolve().then(x => console.log(result));
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
@@ -16,4 +16,4 @@ async function f() {
 }
 function res(result) {
     return Promise.resolve().then(x => console.log(result));
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_simpleFunctionExpression.js

@@ -2,11 +2,11 @@
 
 const /*[#|*/foo/*|]*/ = function () {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
 const foo = async function () {
     const result = await fetch('https://typescriptlang.org');
     console.log(result);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_simpleFunctionExpression.ts

@@ -2,11 +2,11 @@
 
 const /*[#|*/foo/*|]*/ = function () {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
 const foo = async function () {
     const result = await fetch('https://typescriptlang.org');
     console.log(result);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_simpleFunctionExpressionAssignedToBindingPattern.js

@@ -2,11 +2,11 @@
 
 const { length } = /*[#|*/function/*|]*/ () {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
 const { length } = async function () {
     const result = await fetch('https://typescriptlang.org');
     console.log(result);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_simpleFunctionExpressionAssignedToBindingPattern.ts

@@ -2,11 +2,11 @@
 
 const { length } = /*[#|*/function/*|]*/ () {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
 const { length } = async function () {
     const result = await fetch('https://typescriptlang.org');
     console.log(result);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_simpleFunctionExpressionWithName.js

@@ -2,11 +2,11 @@
 
 const foo = function /*[#|*/f/*|]*/() {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
 const foo = async function f() {
     const result = await fetch('https://typescriptlang.org');
     console.log(result);
-} 
+}

tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_simpleFunctionExpressionWithName.ts

@@ -2,11 +2,11 @@
 
 const foo = function /*[#|*/f/*|]*/() {
     return fetch('https://typescriptlang.org').then(result => { console.log(result) });
-} 
+}
 
 // ==ASYNC FUNCTION::Convert to async function==
 
 const foo = async function f() {
     const result = await fetch('https://typescriptlang.org');
     console.log(result);
-} 
+}