improve

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

@@ -6,6 +6,21 @@ type t = typeof t;
 
 const ENUMS = new WeakMap<t.Identifier, PreviousEnumMembers>();
 
+const buildEnumWrapper = template.statement(`
+  (function (ID) {
+    ASSIGNMENTS;
+  })(ID || (ID = {}));
+`);
+
+const buildPureEnumWrapper = template.expression(
+  `
+  /*#__PURE__*/(function (ID) {
+    ASSIGNMENTS;
+  })(ID || {})
+`,
+  { preserveComments: true },
+);
+
 export default function transpileEnum(
   path: NodePath<t.TSEnumDeclaration>,
   t: t,
@@ -18,24 +33,50 @@ export default function transpileEnum(
   }
 
   const name = node.id.name;
-  const { wrapper: fill, data } = enumFill(path, t, node.id);
+  const { fill, data, isPure } = enumFill(path, t, node.id);
 
   switch (path.parent.type) {
     case "BlockStatement":
     case "ExportNamedDeclaration":
     case "Program": {
-      path.insertAfter(fill);
-      if (seen(path.parentPath)) {
-        path.remove();
+      // todo: Consider exclude program with import/export
+      // && !path.parent.body.some(n => t.isImportDeclaration(n) || t.isExportDeclaration(n));
+      const isGlobal = t.isProgram(path.parent);
+
+      if (isPure && isGlobal) {
+        if (seen(path.parentPath)) {
+          path.replaceWith(
+            t.assignmentExpression(
+              "=",
+              t.cloneNode(node.id),
+              buildPureEnumWrapper(fill),
+            ),
+          );
+        } else {
+          path.scope.registerDeclaration(
+            path.replaceWith(
+              t.variableDeclaration("var", [
+                t.variableDeclarator(node.id, buildPureEnumWrapper(fill)),
+              ]),
+            )[0],
+          );
+        }
       } else {
-        // todo: Consider exclude program with import/export
-        // && !path.parent.body.some(n => t.isImportDeclaration(n) || t.isExportDeclaration(n));
-        const isGlobal = t.isProgram(path.parent);
-        path.scope.registerDeclaration(
-          path.replaceWith(makeVar(node.id, t, isGlobal ? "var" : "let"))[0],
-        );
-        ENUMS.set(path.scope.getBindingIdentifier(name), data);
+        path.insertAfter(buildEnumWrapper(fill));
+
+        if (seen(path.parentPath)) {
+          path.remove();
+        } else {
+          path.scope.registerDeclaration(
+            path.replaceWith(
+              t.variableDeclaration(isGlobal ? "var" : "let", [
+                t.variableDeclarator(node.id),
+              ]),
+            )[0],
+          );
+        }
       }
+      ENUMS.set(path.scope.getBindingIdentifier(name), data);
       break;
     }
 
@@ -57,16 +98,6 @@ export default function transpileEnum(
   }
 }
 
-function makeVar(id: t.Identifier, t: t, kind: "var" | "let" | "const") {
-  return t.variableDeclaration(kind, [t.variableDeclarator(id)]);
-}
-
-const buildEnumWrapper = template(`
-  (function (ID) {
-    ASSIGNMENTS;
-  })(ID || (ID = {}));
-`);
-
 const buildStringAssignment = template(`
   ENUM["NAME"] = VALUE;
 `);
@@ -83,7 +114,7 @@ const buildEnumMember = (isString: boolean, options: Record<string, unknown>) =>
  * `(function (E) { ... assignments ... })(E || (E = {}));`
  */
 function enumFill(path: NodePath<t.TSEnumDeclaration>, t: t, id: t.Identifier) {
-  const { enumValues: x, data } = translateEnumValues(path, t);
+  const { enumValues: x, data, isPure } = translateEnumValues(path, t);
   const assignments = x.map(([memberName, memberValue]) =>
     buildEnumMember(t.isStringLiteral(memberValue), {
       ENUM: t.cloneNode(id),
@@ -93,11 +124,12 @@ function enumFill(path: NodePath<t.TSEnumDeclaration>, t: t, id: t.Identifier) {
   );
 
   return {
-    wrapper: buildEnumWrapper({
+    fill: {
       ID: t.cloneNode(id),
       ASSIGNMENTS: assignments,
-    }),
-    data: data,
+    },
+    data,
+    isPure,
   };
 }
 
@@ -141,10 +173,11 @@ export function translateEnumValues(path: NodePath<t.TSEnumDeclaration>, t: t) {
   // Start at -1 so the first enum member is its increment, 0.
   let constValue: number | string | undefined = -1;
   let lastName: string;
+  let isPure = true;
 
-  return {
-    data: seen,
-    enumValues: path.get("members").map(memberPath => {
+  const enumValues: Array<[name: string, value: t.Expression]> = path
+    .get("members")
+    .map(memberPath => {
       const member = memberPath.node;
       const name = t.isIdentifier(member.id) ? member.id.name : member.id.value;
       const initializerPath = memberPath.get("initializer");
@@ -161,6 +194,10 @@ export function translateEnumValues(path: NodePath<t.TSEnumDeclaration>, t: t) {
             value = t.stringLiteral(constValue);
           }
         } else {
+          if (isPure && !initializerPath.isPure()) {
+            isPure = false;
+          }
+
           if (initializerPath.isReferencedIdentifier()) {
             ReferencedIdentifier(initializerPath, {
               t,
@@ -197,7 +234,12 @@ export function translateEnumValues(path: NodePath<t.TSEnumDeclaration>, t: t) {
 
       lastName = name;
       return [name, value];
-    }) as Array<[name: string, value: t.Expression]>,
+    });
+
+  return {
+    isPure,
+    data: seen,
+    enumValues,
   };
 }
 

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

@@ -1,5 +1,4 @@
 // Not type-correct code
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E[E["A"] = true] = "A";
-})(E || (E = {}));
+}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/const/output.js

@@ -1,3 +1,2 @@
 // With --isolatedModules, TSC ignores the "const" modifier when compiling enums
-var E;
-(function (E) {})(E || (E = {}));
+var E = /*#__PURE__*/function (E) {}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/constant-folding/output.js

@@ -1,5 +1,4 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E[E["a"] = 0] = "a";
   E[E["b"] = 3] = "b";
   E[E["c"] = 1] = "c";
@@ -18,4 +17,4 @@ var E;
   E[E["p"] = -3] = "p";
   E[E["q"] = 5.4] = "q";
   E[E["r"] = 6.4] = "r";
-})(E || (E = {}));
+}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/inferred/output.js

@@ -1,5 +1,4 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E[E["x"] = 0] = "x";
   E[E["y"] = 1] = "y";
-})(E || (E = {}));
+}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/inner-references/output.js

@@ -1,5 +1,4 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E[E["a"] = 10] = "a";
   E[E["b"] = 10] = "b";
-})(E || (E = {}));
+}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/mix-references/output.js

@@ -1,10 +1,9 @@
 var x = 10;
-var Foo;
-(function (Foo) {
+var Foo = /*#__PURE__*/function (Foo) {
   Foo[Foo["a"] = 10] = "a";
   Foo[Foo["b"] = 10] = "b";
   Foo[Foo["c"] = 20] = "c";
-})(Foo || (Foo = {}));
+}(Foo || {});
 var Bar;
 (function (Bar) {
   Bar[Bar["D"] = 10] = "D";

packages/babel-plugin-transform-typescript/test/fixtures/enum/non-scoped/output.js

@@ -1,8 +1,7 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E[E["x"] = 1] = "x";
   E[E["y"] = 2] = "y";
-})(E || (E = {}));
-(function (E) {
+}(E || {});
+E = /*#__PURE__*/function (E) {
   E[E["z"] = 3] = "z";
-})(E || (E = {}));
+}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/outer-references/output.js

@@ -1,14 +1,12 @@
-var socketType;
-(function (socketType) {
+var socketType = /*#__PURE__*/function (socketType) {
   socketType[socketType["SOCKET"] = 0] = "SOCKET";
   socketType[socketType["SERVER"] = 1] = "SERVER";
   socketType[socketType["IPC"] = 2] = "IPC";
-})(socketType || (socketType = {}));
-var constants;
-(function (constants) {
+}(socketType || {});
+var constants = /*#__PURE__*/function (constants) {
   constants[constants["SOCKET"] = 0] = "SOCKET";
   constants[constants["SERVER"] = 1] = "SERVER";
   constants[constants["IPC"] = 2] = "IPC";
   constants[constants["UV_READABLE"] = 3] = "UV_READABLE";
   constants[constants["UV_WRITABLE"] = 4] = "UV_WRITABLE";
-})(constants || (constants = {}));
+}(constants || {});

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

@@ -1,4 +1,3 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E["A"] = "Hey";
-})(E || (E = {}));
+}(E || {});

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

@@ -1,7 +1,6 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E[E["A"] = 0] = "A";
   E["B"] = "";
   E[E["A2"] = 0] = "A2";
   E["B2"] = "";
-})(E || (E = {}));
+}(E || {});

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

@@ -1,4 +1,3 @@
-var E;
-(function (E) {
+var E = /*#__PURE__*/function (E) {
   E["A"] = "HALLOWERLD";
-})(E || (E = {}));
+}(E || {});

packages/babel-plugin-transform-typescript/test/fixtures/enum/ts5.0-const-foldable/output.js

@@ -2,18 +2,16 @@
 
 const BaseValue = 10;
 const Prefix = "/data";
-var Values; // 12
-(function (Values) {
+var Values = /*#__PURE__*/function (Values) {
   Values[Values["First"] = 10] = "First";
   Values[Values["Second"] = 11] = "Second";
   Values[Values["Third"] = 12] = "Third";
-})(Values || (Values = {}));
+}(Values || {}); // 12
 const xxx = 100 + Values.First;
 const yyy = xxx;
-var Routes;
-(function (Routes) {
+var Routes = /*#__PURE__*/function (Routes) {
   Routes["Parts"] = "/data/parts";
   Routes["Invoices"] = "/data/invoices";
   Routes["x"] = "10/x";
   Routes["y"] = "110/y";
-})(Routes || (Routes = {}));
+}(Routes || {});

packages/babel-plugin-transform-typescript/test/fixtures/exports/declared-types/output.mjs

@@ -1,19 +1,17 @@
 export class C2 {}
 // everything removed
 export { C2 as C3 }; // only C2->C3
-var BB;
-(function (BB) {
+var BB = /*#__PURE__*/function (BB) {
   BB[BB["K"] = 0] = "K";
-})(BB || (BB = {}));
-(function (BB) {
+}(BB || {});
+BB = /*#__PURE__*/function (BB) {
   BB["L"] = "LL";
-})(BB || (BB = {}));
+}(BB || {});
 export { BB }; // only BB
 
 // everything removed
 export { BB as BB1 }; // BB->BB1
-var BB2;
-(function (BB2) {})(BB2 || (BB2 = {}));
+var BB2 = /*#__PURE__*/function (BB2) {}(BB2 || {});
 function foo() {}
 export { BB2 as BB3, foo }; // only BB2->BB3 and foo
 

packages/babel-plugin-transform-typescript/test/fixtures/exports/export-const-enums/output.mjs

@@ -1,4 +1,3 @@
-var None;
-(function (None) {})(None || (None = {}));
+var None = /*#__PURE__*/function (None) {}(None || {});
 ;
 export {};

packages/babel-plugin-transform-typescript/test/fixtures/imports/enum-id/output.mjs

@@ -1,6 +1,5 @@
-var Enum;
-(function (Enum) {
+var Enum = /*#__PURE__*/function (Enum) {
   Enum[Enum["A"] = 0] = "A";
-})(Enum || (Enum = {}));
+}(Enum || {});
 ;
 export {};

packages/babel-plugin-transform-typescript/test/fixtures/imports/enum-value/output.mjs

@@ -1,6 +1,5 @@
 import { A } from 'lib';
-var Enum;
-(function (Enum) {
+var Enum = /*#__PURE__*/function (Enum) {
   Enum[Enum["id"] = A] = "id";
-})(Enum || (Enum = {}));
+}(Enum || {});
 ;

packages/babel-plugin-transform-typescript/test/fixtures/namespace/clobber-enum/output.mjs

@@ -1,7 +1,6 @@
-var A;
-(function (A) {
+var A = /*#__PURE__*/function (A) {
   A[A["C"] = 2] = "C";
-})(A || (A = {}));
+}(A || {});
 (function (_A) {
   const B = _A.B = 1;
 })(A || (A = {}));

packages/babel-preset-typescript/test/fixtures/flow-compat/ts-valid/output.js

@@ -1,5 +1,4 @@
-var Example;
-(function (Example) {
+var Example = /*#__PURE__*/function (Example) {
   Example[Example["Value"] = 0] = "Value";
-})(Example || (Example = {}));
+}(Example || {});
 foo;

packages/babel-preset-typescript/test/fixtures/flow-compat/tsx-valid/output.js

@@ -1,5 +1,4 @@
-var Example;
-(function (Example) {
+var Example = /*#__PURE__*/function (Example) {
   Example[Example["Value"] = 0] = "Value";
-})(Example || (Example = {}));
+}(Example || {});
 foo;