feat(no-misused-observables): improve report loc for methods (#238)

See tseslint issue 10216. If a property is a function, instead of
reporting the entire function, report either its return type or else use
`getFunctionHeadLocation` to report a more narrow location. See tests
for example.

Author: JasonWeinzierl

src/rules/no-misused-observables.ts

@@ -1,4 +1,5 @@
 import { AST_NODE_TYPES, TSESTree as es, TSESLint as eslint, ESLintUtils } from '@typescript-eslint/utils';
+import { getFunctionHeadLocation, isFunction } from '@typescript-eslint/utils/ast-utils';
 import * as tsutils from 'ts-api-utils';
 import ts from 'typescript';
 import {
@@ -251,10 +252,25 @@ export const noMisusedObservablesRule = ruleCreator({
         return;
       }
 
-      context.report({
-        messageId: 'forbiddenVoidReturnProperty',
-        node: node.value,
-      });
+      if (isFunction(node.value)) {
+        const functionNode = node.value;
+        if (functionNode.returnType) {
+          context.report({
+            messageId: 'forbiddenVoidReturnProperty',
+            node: functionNode.returnType.typeAnnotation,
+          });
+        } else {
+          context.report({
+            messageId: 'forbiddenVoidReturnProperty',
+            loc: getFunctionHeadLocation(functionNode, context.sourceCode),
+          });
+        }
+      } else {
+        context.report({
+          messageId: 'forbiddenVoidReturnProperty',
+          node: node.value,
+        });
+      }
     }
 
     function checkReturnStatement(node: es.ReturnStatement): void {
@@ -277,6 +293,7 @@ export const noMisusedObservablesRule = ruleCreator({
         return current;
       }
       const functionNode = getFunctionNode();
+
       if (
         functionNode?.returnType
         && !isPossiblyFunctionType(functionNode.returnType)

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

@@ -740,7 +740,7 @@ ruleTester({ types: true }).run('no-misused-observables', noMisusedObservablesRu
         type Foo = { bar: () => void };
         const foo: Foo = {
           bar: () => of(42),
-               ~~~~~~~~~~~~ [forbiddenVoidReturnProperty]
+                  ~~ [forbiddenVoidReturnProperty]
         };
       `,
     ),
@@ -752,7 +752,7 @@ ruleTester({ types: true }).run('no-misused-observables', noMisusedObservablesRu
         type Foo = { bar: () => void };
         const foo: Foo = {
           bar(): Observable<number> { return of(42); },
-             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [forbiddenVoidReturnProperty]
+                 ~~~~~~~~~~~~~~~~~~ [forbiddenVoidReturnProperty]
         };
       `,
     ),