Handle ClassDeclaration binding bug in babel

+ (Fixes #365)

This is happening because ClassDeclarations have bindings in two scopes where as FunctionDeclarations have bindings only in the scope where it is defined.

+ babel bug: babel/babel#5156

packages/babel-plugin-minify-mangle-names/__tests__/mangle-names-test.js

@@ -1129,4 +1129,24 @@ describe("mangle-names", () => {
     `);
     expect(transform(source)).toBe(expected);
   });
+
+  it("should fix issue#365 - classDeclaration with unsafe parent scope", () => {
+    const source = unpad(`
+      function foo() {
+        eval("");
+        class A {}
+        class B {}
+      }
+    `);
+    expect(transform(source)).toBe(source);
+  });
+
+  it("should fix classDeclaration with unsafe program scope", () => {
+    const source = unpad(`
+      eval("");
+      class A {}
+      class B {}
+    `);
+    expect(transform(source, { topLevel: true })).toBe(source);
+  });
 });

packages/babel-plugin-minify-mangle-names/src/index.js

@@ -93,7 +93,16 @@ module.exports = ({ types: t, traverse }) => {
         Scopable(path) {
           const {scope} = path;
 
-          if (!mangler.eval && hasEval(scope)) return;
+          if (!mangler.eval) {
+            if (hasEval(scope)) return;
+
+            // ClassDeclaration has binding in two scopes
+            //   1. The scope in which it is declared
+            //   2. The class's own scope
+            // So, when the scope.1 is an unsafeScope, mangling happens in scope.2
+            // To avoid that, we check if it's a class declaration
+            if (path.isClassDeclaration() && hasEval(path.parentPath.scope)) return;
+          }
 
           if (mangler.visitedScopes.has(scope)) return;
           mangler.visitedScopes.add(scope);
@@ -170,7 +179,11 @@ module.exports = ({ types: t, traverse }) => {
             if (isTopLevel) {
               mangler.rename(mangler.program.scope, oldName, next);
             }
+
             // mark the binding as renamed
+            // this is redundant and exists to work around a bug in babel
+            // ClassDeclarations have binding in two scopes
+            // - https://github.com/babel/babel/issues/5156
             binding.renamed = true;
           }
         }