[TS] Correctly transform computed strings and templates in enums (#10555

)

* [TS] Correctly transform computed strings and templates in enums

* Typo [skip ci]

packages/babel-plugin-transform-typescript/src/enum.js

@@ -144,13 +144,12 @@ function evaluate(
   expr,
   seen: PreviousEnumMembers,
 ): number | string | typeof undefined {
-  if (expr.type === "StringLiteral") {
-    return expr.value;
-  }
   return evalConstant(expr);
 
   function evalConstant(expr): number | typeof undefined {
     switch (expr.type) {
+      case "StringLiteral":
+        return expr.value;
       case "UnaryExpression":
         return evalUnaryExpression(expr);
       case "BinaryExpression":
@@ -161,6 +160,11 @@ function evaluate(
         return evalConstant(expr.expression);
       case "Identifier":
         return seen[expr.name];
+      case "TemplateLiteral":
+        if (expr.quasis.length === 1) {
+          return expr.quasis[0].value.cooked;
+        }
+      /* falls through */
       default:
         return undefined;
     }

packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/input.ts

@@ -0,0 +1,3 @@
+enum E {
+  A = `Hey`
+}

packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/output.js

@@ -0,0 +1,5 @@
+var E;
+
+(function (E) {
+  E["A"] = "Hey";
+})(E || (E = {}));

packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/input.ts

@@ -1,4 +1,3 @@
-// Not type-correct code
 enum E {
   A = "HALLO" + "WERLD"
 }

packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/output.js

@@ -1,6 +1,5 @@
-// Not type-correct code
 var E;
 
 (function (E) {
-  E[E["A"] = "HALLO" + "WERLD"] = "A";
+  E["A"] = "HALLOWERLD";
 })(E || (E = {}));