Resolve issue #555

src/lib/parser.ts

@@ -1164,7 +1164,20 @@ export const createParser = (
             let token;
             let key: TwingBaseExpressionNode;
 
-            if ((token = stream.nextIf("STRING")) || (token = stream.nextIf("NAME")) || (token = stream.nextIf("NUMBER"))) {
+            if (token = stream.nextIf("NAME")) {
+                key = createConstantNode(token.value, token.line, token.column);
+
+                // {a} is a shortcut for {a:a}
+                if (stream.test("PUNCTUATION", [',', '}'])) {
+                    elements.push({
+                        key,
+                        value: createNameNode(token.value, token.line, token.column)
+                    });
+                    
+                    continue;
+                }
+            }
+            else if ((token = stream.nextIf("STRING")) || (token = stream.nextIf("NUMBER"))) {
                 key = createConstantNode(token.value, token.line, token.column);
             }
             else if (stream.test("PUNCTUATION", '(')) {

test/tests/integration/expressions/hash/index.ts

@@ -1,2 +1,3 @@
 import "./hash";
 import "./invalid-key";
+import "./with-value-only";

test/tests/integration/expressions/hash/with-value-only.ts

@@ -0,0 +1,15 @@
+import {runTest} from "../../TestBase";
+
+runTest({
+   description: 'Hash key can be omitted if it is the same as the variable name',
+   templates: {
+       "index.twig": `
+{% set foo = "foo" %}
+{% set hash = { foo, bar: "bar" } %}
+{{ hash|join }}
+`
+   },
+    expectation: `
+foobar
+`
+});