[ts] Strip type-only namespaces

babel · Jul 19, 2023 · c2b0a0d · c2b0a0d
1 parent f28ff8a
commit c2b0a0d
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Showing 3 changed files with 100 additions and 24 deletions.
diff --git a/packages/babel-plugin-transform-typescript/src/namespace.ts b/packages/babel-plugin-transform-typescript/src/namespace.ts
@@ -24,7 +24,9 @@ export default function transpileNamespace(
   const name = path.node.id.name;
   const value = handleNested(path, t.cloneNode(path.node, true));
   const bound = path.scope.hasOwnBinding(name);
-  if (path.parent.type === "ExportNamedDeclaration") {
+  if (value === null) {
+    path.remove();
+  } else if (path.parent.type === "ExportNamedDeclaration") {
     if (!bound) {
       path.parentPath.insertAfter(value);
       path.replaceWith(getDeclaration(name));
@@ -119,7 +121,7 @@ function handleNested(
   path: NodePath,
   node: t.TSModuleDeclaration,
   parentExport?: t.Expression,
-) {
+): t.Statement | null {
   const names = new Set();
   const realName = node.id;
   t.assertIdentifier(realName);
@@ -134,6 +136,8 @@ function handleNested(
       //   }
       [t.exportNamedDeclaration(node.body)];
 
+  let isEmpty = true;
+
   for (let i = 0; i < namespaceTopLevel.length; i++) {
     const subNode = namespaceTopLevel[i];
 
@@ -146,26 +150,31 @@ function handleNested(
         }
 
         const transformed = handleNested(path, subNode);
-        const moduleName = subNode.id.name;
-        if (names.has(moduleName)) {
-          namespaceTopLevel[i] = transformed;
-        } else {
-          names.add(moduleName);
-          namespaceTopLevel.splice(
-            i++,
-            1,
-            getDeclaration(moduleName),
-            transformed,
-          );
+        if (transformed !== null) {
+          isEmpty = false;
+          const moduleName = subNode.id.name;
+          if (names.has(moduleName)) {
+            namespaceTopLevel[i] = transformed;
+          } else {
+            names.add(moduleName);
+            namespaceTopLevel.splice(
+              i++,
+              1,
+              getDeclaration(moduleName),
+              transformed,
+            );
+          }
         }
         continue;
       }
       case "TSEnumDeclaration":
       case "FunctionDeclaration":
       case "ClassDeclaration":
+        isEmpty = false;
         names.add(subNode.id.name);
         continue;
       case "VariableDeclaration": {
+        isEmpty = false;
         // getBindingIdentifiers returns an object without prototype.
         // eslint-disable-next-line guard-for-in
         for (const name in t.getBindingIdentifiers(subNode)) {
@@ -174,6 +183,7 @@ function handleNested(
         continue;
       }
       default:
+        isEmpty &&= t.isTypeScript(subNode);
         // Neither named declaration nor export, continue to next item.
         continue;
       case "ExportNamedDeclaration":
@@ -189,6 +199,7 @@ function handleNested(
       case "TSEnumDeclaration":
       case "FunctionDeclaration":
       case "ClassDeclaration": {
+        isEmpty = false;
         const itemName = subNode.declaration.id.name;
         names.add(itemName);
         namespaceTopLevel.splice(
@@ -206,6 +217,7 @@ function handleNested(
         break;
       }
       case "VariableDeclaration": {
+        isEmpty = false;
         const nodes = handleVariableDeclaration(
           subNode.declaration,
           name,
@@ -225,22 +237,27 @@ function handleNested(
           subNode.declaration,
           t.identifier(name),
         );
-        const moduleName = subNode.declaration.id.name;
-        if (names.has(moduleName)) {
-          namespaceTopLevel[i] = transformed;
-        } else {
-          names.add(moduleName);
-          namespaceTopLevel.splice(
-            i++,
-            1,
-            getDeclaration(moduleName),
-            transformed,
-          );
+        if (transformed !== null) {
+          isEmpty = false;
+          const moduleName = subNode.declaration.id.name;
+          if (names.has(moduleName)) {
+            namespaceTopLevel[i] = transformed;
+          } else {
+            names.add(moduleName);
+            namespaceTopLevel.splice(
+              i++,
+              1,
+              getDeclaration(moduleName),
+              transformed,
+            );
+          }
         }
       }
     }
   }
 
+  if (isEmpty) return null;
+
   // {}
   let fallthroughValue: t.Expression = t.objectExpression([]);
 

diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/namespace/empty-removed/input.ts b/packages/babel-plugin-transform-typescript/test/fixtures/namespace/empty-removed/input.ts
@@ -0,0 +1,22 @@
+namespace a {
+  namespace b {}
+  namespace c { var x }
+  namespace d {
+    namespace e {}
+  }
+}
+
+namespace WithTypes {
+  namespace a { type A = 1 }
+  namespace b { interface B {} }
+  namespace c { import C = a }
+  namespace d { declare class D {} }
+}
+
+namespace WithValues {
+  namespace a { class A {} }
+  namespace b { enum B {} }
+  namespace c { function C() {} }
+  namespace d { var D }
+  namespace e { E; }
+}
diff --git a/packages/babel-plugin-transform-typescript/test/fixtures/namespace/empty-removed/output.mjs b/packages/babel-plugin-transform-typescript/test/fixtures/namespace/empty-removed/output.mjs
@@ -0,0 +1,37 @@
+let a;
+(function (_a) {
+  let c;
+  (function (_c) {
+    var x;
+  })(c || (c = {}));
+})(a || (a = {}));
+let WithTypes;
+(function (_WithTypes) {
+  let d;
+  (function (_d2) {})(d || (d = {}));
+})(WithTypes || (WithTypes = {}));
+let WithValues;
+(function (_WithValues) {
+  let a;
+  (function (_a3) {
+    class A {}
+  })(a || (a = {}));
+  let b;
+  (function (_b3) {
+    let B = /*#__PURE__*/function (B) {
+      return B;
+    }({});
+  })(b || (b = {}));
+  let c;
+  (function (_c3) {
+    function C() {}
+  })(c || (c = {}));
+  let d;
+  (function (_d3) {
+    var D;
+  })(d || (d = {}));
+  let e;
+  (function (_e2) {
+    E;
+  })(e || (e = {}));
+})(WithValues || (WithValues = {}));