feat(groq): this attribute

Author: saiichihashimoto

packages/groq/src/index.test.ts

@@ -69,6 +69,14 @@ describe("groq", () => {
     >().toStrictEqual<typeof UNIQUE_VALUE>();
   });
 
+  it("key", () => {
+    const UNIQUE_VALUE: unique symbol = Symbol("");
+
+    expectType<
+      ExecuteQuery<"key", Scope<any, { key: typeof UNIQUE_VALUE }, any>>
+    >().toStrictEqual<typeof UNIQUE_VALUE>();
+  });
+
   it("*", () =>
     expectType<
       ExecuteQuery<

packages/groq/src/index.ts

@@ -143,10 +143,21 @@ type This<
     : never
   : never;
 
+/**
+ * @link https://sanity-io.github.io/GROQ/GROQ-1.revision1/#ThisAttribute
+ */
+type ThisAttribute<
+  TExpression extends string,
+  TScope extends Scope<any, any, any>
+> = TScope extends Scope<any, infer Value, any>
+  ? TExpression extends keyof Value
+    ? Value[TExpression]
+    : never
+  : never;
+
 /**
  * @link https://sanity-io.github.io/GROQ/GROQ-1.revision1/#SimpleExpression
  *
- * @todo ThisAttribute
  * @todo FuncCall
  */
 type SimpleExpression<
@@ -155,7 +166,8 @@ type SimpleExpression<
 > =
   | Everything<TExpression, TScope>
   | Parent<TExpression, TScope>
-  | This<TExpression, TScope>;
+  | This<TExpression, TScope>
+  | ThisAttribute<TExpression, TScope>;
 
 /**
  * @link https://sanity-io.github.io/GROQ/GROQ-1.revision1/#Parenthesis