Make @babel/plugin-class-features a normal helper package (#9083)

* Make @babel/plugin-class-features a normal helper package

This effectively disallows using it directly.

* Rename helper

* Style

* Don't add prefix to plugin name

* Move private methods plugin

packages/babel-helper-create-class-features-plugin/src/misc.js

@@ -0,0 +1,111 @@
+import { template, traverse, types as t } from "@babel/core";
+import { environmentVisitor } from "@babel/helper-replace-supers";
+
+const findBareSupers = traverse.visitors.merge([
+  {
+    Super(path) {
+      const { node, parentPath } = path;
+      if (parentPath.isCallExpression({ callee: node })) {
+        this.push(parentPath);
+      }
+    },
+  },
+  environmentVisitor,
+]);
+
+const referenceVisitor = {
+  "TSTypeAnnotation|TypeAnnotation"(path) {
+    path.skip();
+  },
+
+  ReferencedIdentifier(path) {
+    if (this.scope.hasOwnBinding(path.node.name)) {
+      this.scope.rename(path.node.name);
+      path.skip();
+    }
+  },
+};
+
+const classFieldDefinitionEvaluationTDZVisitor = traverse.visitors.merge([
+  {
+    ReferencedIdentifier(path) {
+      if (
+        this.classBinding &&
+        this.classBinding === path.scope.getBinding(path.node.name)
+      ) {
+        const classNameTDZError = this.file.addHelper("classNameTDZError");
+        const throwNode = t.callExpression(classNameTDZError, [
+          t.stringLiteral(path.node.name),
+        ]);
+
+        path.replaceWith(t.sequenceExpression([throwNode, path.node]));
+        path.skip();
+      }
+    },
+  },
+  environmentVisitor,
+]);
+
+export function injectInitialization(path, constructor, nodes, renamer) {
+  if (!nodes.length) return;
+
+  const isDerived = !!path.node.superClass;
+
+  if (!constructor) {
+    const newConstructor = t.classMethod(
+      "constructor",
+      t.identifier("constructor"),
+      [],
+      t.blockStatement([]),
+    );
+
+    if (isDerived) {
+      newConstructor.params = [t.restElement(t.identifier("args"))];
+      newConstructor.body.body.push(template.statement.ast`super(...args)`);
+    }
+
+    [constructor] = path.get("body").unshiftContainer("body", newConstructor);
+  }
+
+  if (renamer) {
+    renamer(referenceVisitor, { scope: constructor.scope });
+  }
+
+  if (isDerived) {
+    const bareSupers = [];
+    constructor.traverse(findBareSupers, bareSupers);
+    for (const bareSuper of bareSupers) {
+      bareSuper.insertAfter(nodes);
+    }
+  } else {
+    constructor.get("body").unshiftContainer("body", nodes);
+  }
+}
+
+export function extractComputedKeys(ref, path, computedPaths, file) {
+  const declarations = [];
+
+  for (const computedPath of computedPaths) {
+    computedPath.traverse(classFieldDefinitionEvaluationTDZVisitor, {
+      classBinding: path.node.id && path.scope.getBinding(path.node.id.name),
+      file,
+    });
+
+    const computedNode = computedPath.node;
+    // Make sure computed property names are only evaluated once (upon class definition)
+    // and in the right order in combination with static properties
+    if (!computedPath.get("key").isConstantExpression()) {
+      const ident = path.scope.generateUidIdentifierBasedOnNode(
+        computedNode.key,
+      );
+      declarations.push(
+        t.variableDeclaration("var", [
+          t.variableDeclarator(ident, computedNode.key),
+        ]),
+      );
+      computedNode.key = t.cloneNode(ident);
+    }
+  }
+
+  return declarations;
+}