From abce0ef49d4f3b204b9d570b763839101772a56a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Mon, 4 Nov 2019 19:22:49 +0100
Subject: [PATCH] [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 | 10 +++++++---
 .../test/fixtures/enum/string-value-template/input.ts  |  3 +++
 .../test/fixtures/enum/string-value-template/output.js |  5 +++++
 .../enum/{string-values => string-value}/input.ts      |  0
 .../enum/{string-values => string-value}/output.js     |  0
 .../test/fixtures/enum/string-values-computed/input.ts |  1 -
 .../fixtures/enum/string-values-computed/output.js     |  3 +--
 7 files changed, 16 insertions(+), 6 deletions(-)
 create mode 100644 packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/input.ts
 create mode 100644 packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/output.js
 rename packages/babel-plugin-transform-typescript/test/fixtures/enum/{string-values => string-value}/input.ts (100%)
 rename packages/babel-plugin-transform-typescript/test/fixtures/enum/{string-values => string-value}/output.js (100%)

diff --git a/packages/babel-plugin-transform-typescript/src/enum.js b/packages/babel-plugin-transform-typescript/src/enum.js
index 11c7b5376d..3b604e2e8f 100644
--- a/packages/babel-plugin-transform-typescript/src/enum.js
+++ b/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;
     }
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/input.ts b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/input.ts
new file mode 100644
index 0000000000..01086419ea
--- /dev/null
+++ b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/input.ts
@@ -0,0 +1,3 @@
+enum E {
+  A = `Hey`
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/output.js b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value-template/output.js
new file mode 100644
index 0000000000..dfc0f72fcd
--- /dev/null
+++ b/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 = {}));
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values/input.ts b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value/input.ts
similarity index 100%
rename from packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values/input.ts
rename to packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value/input.ts
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values/output.js b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value/output.js
similarity index 100%
rename from packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values/output.js
rename to packages/babel-plugin-transform-typescript/test/fixtures/enum/string-value/output.js
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/input.ts b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/input.ts
index ac52806fb9..06e9b00f06 100644
--- a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/input.ts
+++ b/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"
 }
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/output.js b/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/output.js
index e449a1ca23..a0f3ea2ca8 100644
--- a/packages/babel-plugin-transform-typescript/test/fixtures/enum/string-values-computed/output.js
+++ b/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 = {}));