feat(eslint-plugin): [prom-func-async] report only function head (#2872)

packages/eslint-plugin/src/rules/promise-function-async.ts

@@ -91,6 +91,7 @@ export default util.createRule<Options, MessageIds>({
     ]);
     const parserServices = util.getParserServices(context);
     const checker = parserServices.program.getTypeChecker();
+    const sourceCode = context.getSourceCode();
 
     function validateNode(
       node:
@@ -140,12 +141,14 @@ export default util.createRule<Options, MessageIds>({
         return context.report({
           messageId: 'missingAsync',
           node,
+          loc: util.getFunctionHeadLoc(node, sourceCode),
         });
       }
 
       context.report({
         messageId: 'missingAsync',
         node,
+        loc: util.getFunctionHeadLoc(node, sourceCode),
         fix: fixer => {
           if (
             node.parent &&

packages/eslint-plugin/src/util/explicitReturnTypeUtils.ts

@@ -2,75 +2,16 @@ import {
   TSESTree,
   AST_NODE_TYPES,
   TSESLint,
-  AST_TOKEN_TYPES,
 } from '@typescript-eslint/experimental-utils';
 import { isTypeAssertion, isConstructor, isSetter } from './astUtils';
+import { getFunctionHeadLoc } from './getFunctionHeadLoc';
 import { nullThrows, NullThrowsReasons } from './nullThrows';
 
 type FunctionExpression =
   | TSESTree.ArrowFunctionExpression
   | TSESTree.FunctionExpression;
 type FunctionNode = FunctionExpression | TSESTree.FunctionDeclaration;
 
-/**
- * Creates a report location for the given function.
- * The location only encompasses the "start" of the function, and not the body
- *
- * eg.
- * function foo(args) {}
- * ^^^^^^^^^^^^^^^^^^
- *
- * get y(args) {}
- * ^^^^^^^^^^^
- *
- * const x = (args) => {}
- *           ^^^^^^^^^
- */
-function getReporLoc(
-  node: FunctionNode,
-  sourceCode: TSESLint.SourceCode,
-): TSESTree.SourceLocation {
-  /**
-   * Returns start column position
-   * @param node
-   */
-  function getLocStart(): TSESTree.LineAndColumnData {
-    /* highlight method name */
-    const parent = node.parent;
-    if (
-      parent &&
-      (parent.type === AST_NODE_TYPES.MethodDefinition ||
-        (parent.type === AST_NODE_TYPES.Property && parent.method))
-    ) {
-      return parent.loc.start;
-    }
-
-    return node.loc.start;
-  }
-
-  /**
-   * Returns end column position
-   * @param node
-   */
-  function getLocEnd(): TSESTree.LineAndColumnData {
-    /* highlight `=>` */
-    if (node.type === AST_NODE_TYPES.ArrowFunctionExpression) {
-      return sourceCode.getTokenBefore(
-        node.body,
-        token =>
-          token.type === AST_TOKEN_TYPES.Punctuator && token.value === '=>',
-      )!.loc.end;
-    }
-
-    return sourceCode.getTokenBefore(node.body)!.loc.end;
-  }
-
-  return {
-    start: getLocStart(),
-    end: getLocEnd(),
-  };
-}
-
 /**
  * Checks if a node is a variable declarator with a type annotation.
  * ```
@@ -327,7 +268,7 @@ function checkFunctionReturnType(
     return;
   }
 
-  report(getReporLoc(node, sourceCode));
+  report(getFunctionHeadLoc(node, sourceCode));
 }
 
 /**

packages/eslint-plugin/src/util/getFunctionHeadLoc.ts

@@ -0,0 +1,79 @@
+import {
+  AST_NODE_TYPES,
+  AST_TOKEN_TYPES,
+  TSESLint,
+  TSESTree,
+} from '@typescript-eslint/experimental-utils';
+
+type FunctionNode =
+  | TSESTree.ArrowFunctionExpression
+  | TSESTree.FunctionExpression
+  | TSESTree.FunctionDeclaration;
+
+/**
+ * Creates a report location for the given function.
+ * The location only encompasses the "start" of the function, and not the body
+ *
+ * eg.
+ *
+ * ```
+ * function foo(args) {}
+ * ^^^^^^^^^^^^^^^^^^
+ *
+ * get y(args) {}
+ * ^^^^^^^^^^^
+ *
+ * const x = (args) => {}
+ *           ^^^^^^^^^
+ * ```
+ */
+export function getFunctionHeadLoc(
+  node: FunctionNode,
+  sourceCode: TSESLint.SourceCode,
+): TSESTree.SourceLocation {
+  function getLocStart(): TSESTree.LineAndColumnData {
+    if (node.parent && node.parent.type === AST_NODE_TYPES.MethodDefinition) {
+      // return the start location for class method
+
+      if (node.parent.decorators && node.parent.decorators.length > 0) {
+        // exclude decorators
+        return sourceCode.getTokenAfter(
+          node.parent.decorators[node.parent.decorators.length - 1],
+        )!.loc.start;
+      }
+
+      return node.parent.loc.start;
+    }
+
+    if (
+      node.parent &&
+      node.parent.type === AST_NODE_TYPES.Property &&
+      node.parent.method
+    ) {
+      // return the start location for object method shorthand
+      return node.parent.loc.start;
+    }
+
+    // return the start location for a regular function
+    return node.loc.start;
+  }
+
+  function getLocEnd(): TSESTree.LineAndColumnData {
+    if (node.type === AST_NODE_TYPES.ArrowFunctionExpression) {
+      // find the end location for arrow function expression
+      return sourceCode.getTokenBefore(
+        node.body,
+        token =>
+          token.type === AST_TOKEN_TYPES.Punctuator && token.value === '=>',
+      )!.loc.end;
+    }
+
+    // return the end location for a regular function
+    return sourceCode.getTokenBefore(node.body)!.loc.end;
+  }
+
+  return {
+    start: getLocStart(),
+    end: getLocEnd(),
+  };
+}

packages/eslint-plugin/src/util/index.ts

@@ -3,6 +3,7 @@ import { ESLintUtils } from '@typescript-eslint/experimental-utils';
 export * from './astUtils';
 export * from './collectUnusedVariables';
 export * from './createRule';
+export * from './getFunctionHeadLoc';
 export * from './isTypeReadonly';
 export * from './misc';
 export * from './nullThrows';

packages/eslint-plugin/tests/rules/promise-function-async.test.ts

@@ -611,6 +611,25 @@ async function foo(): Promise<string> | SPromise<boolean> {
   return Math.random() > 0.5
     ? Promise.resolve('value')
     : Promise.resolve(false);
+}
+      `,
+    },
+    {
+      code: `
+class Test {
+  @decorator
+  public test() {
+    return Promise.resolve(123);
+  }
+}
+      `,
+      errors: [{ line: 4, column: 3, messageId }],
+      output: `
+class Test {
+  @decorator
+  public async test() {
+    return Promise.resolve(123);
+  }
 }
       `,
     },