Fix the support of arguments in private get/set method (#16307)

* fix arguments

* Update packages/babel-plugin-transform-private-methods/test/fixtures/accessors/arguments/exec.js

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

* review

* fix types

---------

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

packages/babel-helper-create-class-features-plugin/src/fields.ts

@@ -1312,11 +1312,25 @@ function buildPrivateMethodDeclaration(
     (isGetter || isSetter) &&
     !privateFieldsAsProperties
   ) {
-    const thisArg = prop.get("body").scope.generateUidIdentifier("this");
-    // eslint-disable-next-line @typescript-eslint/no-use-before-define
-    prop.traverse(thisContextVisitor, {
+    const scope = prop.get("body").scope;
+    const thisArg = scope.generateUidIdentifier("this");
+    const state: ReplaceThisState = {
       thisRef: thisArg,
-    });
+      argumentsPath: [],
+    };
+    // eslint-disable-next-line @typescript-eslint/no-use-before-define
+    prop.traverse(thisContextVisitor, state);
+    if (state.argumentsPath.length) {
+      const argumentsId = scope.generateUidIdentifier("arguments");
+      scope.push({
+        id: argumentsId,
+        init: template.expression.ast`[].slice.call(arguments, 1)`,
+      });
+      for (const path of state.argumentsPath) {
+        path.replaceWith(t.cloneNode(argumentsId));
+      }
+    }
+
     params.unshift(t.cloneNode(thisArg));
   }
 
@@ -1357,12 +1371,18 @@ type ReplaceThisState = {
   thisRef: t.Identifier;
   needsClassRef?: boolean;
   innerBinding?: t.Identifier | null;
+  argumentsPath?: NodePath<t.Identifier>[];
 };
 
 type ReplaceInnerBindingReferenceState = ReplaceThisState;
 
 const thisContextVisitor = traverse.visitors.merge<ReplaceThisState>([
   {
+    Identifier(path, state) {
+      if (state.argumentsPath && path.node.name === "arguments") {
+        state.argumentsPath.push(path);
+      }
+    },
     UnaryExpression(path) {
       // Replace `delete this` with `true`
       const { node } = path;

packages/babel-plugin-transform-private-methods/test/fixtures/accessors/arguments/exec.js

@@ -0,0 +1,33 @@
+class Cl {
+  #privateField = "top secret string";
+
+  constructor() {
+    this.publicField = "not secret string";
+  }
+
+  get #privateFieldValue() {
+    expect(arguments.length).toBe(0);
+    return this.#privateField;
+  }
+
+  set #privateFieldValue(newValue) {
+    expect(arguments.length).toBe(1);
+    this.#privateField = newValue;
+  }
+
+  publicGetPrivateField() {
+    return this.#privateFieldValue;
+  }
+
+  publicSetPrivateField(newValue) {
+    this.#privateFieldValue = newValue;
+  }
+}
+
+const cl = new Cl();
+
+expect(cl.publicGetPrivateField()).toEqual("top secret string");
+
+cl.publicSetPrivateField("new secret string");
+expect(cl.publicGetPrivateField()).toEqual("new secret string");
+

packages/babel-plugin-transform-private-methods/test/fixtures/accessors/arguments/input.js

@@ -0,0 +1,25 @@
+class Cl {
+  #privateField = "top secret string";
+
+  constructor() {
+    this.publicField = "not secret string";
+  }
+
+  get #privateFieldValue() {
+    expect(arguments.length).toBe(0);
+    return this.#privateField;
+  }
+
+  set #privateFieldValue(newValue) {
+    expect(arguments.length).toBe(1);
+    this.#privateField = newValue;
+  }
+
+  publicGetPrivateField() {
+    return this.#privateFieldValue;
+  }
+
+  publicSetPrivateField(newValue) {
+    this.#privateFieldValue = newValue;
+  }
+}

packages/babel-plugin-transform-private-methods/test/fixtures/accessors/arguments/output.js

@@ -0,0 +1,25 @@
+var _privateField = /*#__PURE__*/new WeakMap();
+var _Cl_brand = /*#__PURE__*/new WeakSet();
+class Cl {
+  constructor() {
+    babelHelpers.classPrivateMethodInitSpec(this, _Cl_brand);
+    babelHelpers.classPrivateFieldInitSpec(this, _privateField, "top secret string");
+    this.publicField = "not secret string";
+  }
+  publicGetPrivateField() {
+    return babelHelpers.classPrivateGetter(_Cl_brand, this, _get_privateFieldValue);
+  }
+  publicSetPrivateField(newValue) {
+    babelHelpers.classPrivateSetter(_Cl_brand, _set_privateFieldValue, this, newValue);
+  }
+}
+function _get_privateFieldValue(_this) {
+  var _arguments = [].slice.call(arguments, 1);
+  expect(_arguments.length).toBe(0);
+  return babelHelpers.classPrivateFieldGet2(_privateField, _this);
+}
+function _set_privateFieldValue(_this2, newValue) {
+  var _arguments2 = [].slice.call(arguments, 1);
+  expect(_arguments2.length).toBe(1);
+  babelHelpers.classPrivateFieldSet2(_privateField, _this2, newValue);
+}