fix(mangle): handle inferred names for functions (#842)

* fix(mangle): handle inferred names for functions

The t.NOT_LOCAL_BINDING symbol used in plugin-function-name
(https://github.com/babel/babel/blob/bd98041321c60737ddcacd1ad7e056ef6de31879/packages/babel-helper-function-name/src/index.js#L206)
is causing this issue.

This was added in babel/babel#3298

The problem is the binding identifier is NOT registered (skipped) during
crawl and the mangler finds the first safe identifier which ultimately
collides with this name during runtime.

So, we register the binding and don't respect the t.NOT_LOCAL_BINDING.

Fix #829

* fix lint errors

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

@@ -139,6 +139,27 @@ module.exports = babel => {
           });
         },
 
+        /**
+         * This is required because after function name transformation
+         * plugin (part of es2015), the function name is NOT added to the
+         * scope's bindings. So to fix this issue, we simply add a hack to
+         * handle that case - fix it to the scope tree.
+         *
+         * Related:
+         * - https://github.com/babel/minify/issues/829
+         */
+        BindingIdentifier(path) {
+          if (
+            // the parent has this id as the name
+            (path.parentPath.isFunctionExpression({ id: path.node }) ||
+              path.parentPath.isClassExpression({ id: path.node })) &&
+            // and the id isn't yet added to the scope
+            !hop.call(path.parentPath.scope.bindings, path.node.name)
+          ) {
+            path.parentPath.scope.registerBinding("local", path.parentPath);
+          }
+        },
+
         /**
          * This is necessary because, in Babel, the scope.references
          * does NOT contain the references in that scope. Only the program

packages/babel-preset-minify/__tests__/minify-env-tests.js

@@ -196,4 +196,59 @@ describe("preset along with env", () => {
       console.log(foo);
     `
   );
+
+  thePlugin(
+    "should fix issue#829 mangling after function name",
+    `
+      function foo() {
+        let con = console;
+
+        return {
+          a(bar) {
+            con.log(bar);
+          }
+        };
+      }
+    `,
+    `
+      function foo() {
+        var b = console;
+        return {
+          a: function d(c) {
+            b.log(c);
+          }
+        };
+      }
+    `
+  );
+
+  thePlugin(
+    "should fix issue#829 mangling after function name 2",
+    `
+      function bar() {
+        var b = console;
+        return {
+          a: class {
+            constructor(bar) {
+              b.log(bar);
+            }
+          }
+        };
+      }
+    `,
+    `
+      function _classCallCheck(a, b) { if (!(a instanceof b)) throw new TypeError("Cannot call a class as a function"); }
+
+      function bar() {
+        var c = console;
+        return {
+          a: function b(a) {
+            "use strict";
+
+            _classCallCheck(this, b), c.log(a);
+          }
+        };
+      }
+    `
+  );
 });