Use the same logic for determinign the key between prop-types and no-unused-prop-types

Author: jseminck

lib/rules/no-unused-prop-types.js

@@ -265,7 +265,7 @@ module.exports = {
      */
     function getKeyValue(node) {
       if (node.type === 'ObjectTypeProperty') {
-        const tokens = context.getFirstTokens(node, {count: 1, filter: tokenNode => tokenNode.type === 'Identifier'});
+        const tokens = context.getFirstTokens(node, {count: 1, filter: tokenNode => ['Identifier', 'String'].includes(tokenNode.type)});
         return tokens[0].value;
       }
       const key = node.key || node.argument;

lib/rules/prop-types.js

@@ -346,11 +346,8 @@ module.exports = {
      */
     function getKeyValue(node) {
       if (node.type === 'ObjectTypeProperty') {
-        const tokens = context.getFirstTokens(node, 2);
-        return (tokens[0].value === '+' || tokens[0].value === '-'
-          ? tokens[1].value
-          : stripQuotes(tokens[0].value)
-        );
+        const tokens = context.getFirstTokens(node, {count: 1, filter: tokenNode => ['Identifier', 'String'].includes(tokenNode.type)});
+        return stripQuotes(tokens[0].value);
       }
       const key = node.key || node.argument;
       return key.type === 'Identifier' ? key.name : key.value;