Website Structure

Frontend-Learner/node_modules/oxc-parser/src-js/raw-transfer/node-array.js

@@ -0,0 +1,365 @@
+import { constructorError, TOKEN } from "./lazy-common.js";
+
+// Internal symbol to get `NodeArray` from a proxy wrapping a `NodeArray`.
+//
+// Methods of `NodeArray` are called with `this` being the proxy, rather than the `NodeArray` itself.
+// They can "unwrap" the proxy by getting `this[ARRAY]`, and the `get` proxy trap will return
+// the actual `NodeArray`.
+//
+// This symbol is not exported, and it is not actually defined on `NodeArray`s, so user cannot obtain it
+// via `Object.getOwnPropertySymbols` or `Reflect.ownKeys`. Therefore user code cannot unwrap the proxy.
+const ARRAY = Symbol();
+
+// Functions to get internal properties of a `NodeArray`. Initialized in class static block below.
+let getInternalFromProxy, getLength, getElement;
+
+/**
+ * An array of AST nodes where elements are deserialized lazily upon access.
+ *
+ * Extends `Array` to make `Array.isArray` return `true` for a `NodeArray`.
+ *
+ * TODO: Other methods could maybe be more optimal, avoiding going via proxy multiple times
+ * e.g. `some`, `indexOf`.
+ */
+export class NodeArray extends Array {
+  #internal;
+
+  /**
+   * Create a `NodeArray`.
+   *
+   * Constructor does not actually return a `NodeArray`, but one wrapped in a `Proxy`.
+   * The proxy intercepts accesses to elements and lazily deserializes them,
+   * and blocks mutation of elements or `length` property.
+   *
+   * @class
+   * @param {number} pos - Buffer position of first element
+   * @param {number} length - Number of elements
+   * @param {number} stride - Element size in bytes
+   * @param {Function} construct - Function to deserialize element
+   * @param {Object} ast - AST object
+   * @returns {Proxy<NodeArray>} - `NodeArray` wrapped in a `Proxy`
+   */
+  constructor(pos, length, stride, construct, ast) {
+    if (ast?.token !== TOKEN) constructorError();
+
+    super();
+    this.#internal = { pos, length, ast, stride, construct };
+    return new Proxy(this, PROXY_HANDLERS);
+  }
+
+  // Allow `arr.filter`, `arr.map` etc.
+  static [Symbol.species] = Array;
+
+  // Override `values` method with a more efficient one that avoids going via proxy for every iteration.
+  // TODO: Benchmark to check that this is actually faster.
+  values() {
+    return new NodeArrayValuesIterator(this);
+  }
+
+  // Override `keys` method with a more efficient one that avoids going via proxy for every iteration.
+  // TODO: Benchmark to check that this is actually faster.
+  keys() {
+    return new NodeArrayKeysIterator(this);
+  }
+
+  // Override `entries` method with a more efficient one that avoids going via proxy for every iteration.
+  // TODO: Benchmark to check that this is actually faster.
+  entries() {
+    return new NodeArrayEntriesIterator(this);
+  }
+
+  // This method is overwritten with reference to `values` method below.
+  // Defining dummy method here to prevent the later assignment altering the shape of class prototype.
+  [Symbol.iterator]() {}
+
+  /**
+   * Override `slice` method to return a `NodeArray`.
+   *
+   * @this {NodeArray}
+   * @param {*} start - Start of slice
+   * @param {*} end - End of slice
+   * @returns {NodeArray} - `NodeArray` containing slice of this one
+   */
+  slice(start, end) {
+    const internal = this[ARRAY].#internal,
+      { length } = internal;
+
+    start = toInt(start);
+    if (start < 0) {
+      start = length + start;
+      if (start < 0) start = 0;
+    }
+
+    if (end === void 0) {
+      end = length;
+    } else {
+      end = toInt(end);
+      if (end < 0) {
+        end += length;
+        if (end < 0) end = 0;
+      } else if (end > length) {
+        end = length;
+      }
+    }
+
+    let sliceLength = end - start;
+    if (sliceLength <= 0 || start >= length) {
+      start = 0;
+      sliceLength = 0;
+    }
+
+    const { stride } = internal;
+    return new NodeArray(
+      internal.pos + start * stride,
+      sliceLength,
+      stride,
+      internal.construct,
+      internal.ast,
+    );
+  }
+
+  // Make `console.log` deserialize all elements.
+  [Symbol.for("nodejs.util.inspect.custom")]() {
+    const values = [...this.values()];
+    Object.setPrototypeOf(values, DebugNodeArray.prototype);
+    return values;
+  }
+
+  static {
+    /**
+     * Get internal properties of `NodeArray`, given a proxy wrapping a `NodeArray`.
+     * @param {Proxy} proxy - Proxy wrapping `NodeArray` object
+     * @returns {Object} - Internal properties object
+     */
+    getInternalFromProxy = (proxy) => proxy[ARRAY].#internal;
+
+    /**
+     * Get length of `NodeArray`.
+     * @param {NodeArray} arr - `NodeArray` object
+     * @returns {number} - Array length
+     */
+    getLength = (arr) => arr.#internal.length;
+
+    /**
+     * Get element of `NodeArray` at index `index`.
+     *
+     * @param {NodeArray} arr - `NodeArray` object
+     * @param {number} index - Index of element to get
+     * @returns {*} - Element at index `index`, or `undefined` if out of bounds
+     */
+    getElement = (arr, index) => {
+      const internal = arr.#internal;
+      if (index >= internal.length) return void 0;
+      return (0, internal.construct)(internal.pos + index * internal.stride, internal.ast);
+    };
+  }
+}
+
+// oxlint-disable-next-line typescript/unbound-method
+NodeArray.prototype[Symbol.iterator] = NodeArray.prototype.values;
+
+/**
+ * Iterator over values of a `NodeArray`.
+ * Returned by `values` method, and also used as iterator for `for (const node of nodeArray) {}`.
+ */
+class NodeArrayValuesIterator {
+  #internal;
+
+  constructor(proxy) {
+    const internal = getInternalFromProxy(proxy),
+      { pos, stride } = internal;
+
+    this.#internal = {
+      pos,
+      endPos: pos + internal.length * stride,
+      ast: internal.ast,
+      construct: internal.construct,
+      stride,
+    };
+  }
+
+  next() {
+    const internal = this.#internal,
+      { pos } = internal;
+    if (pos === internal.endPos) return { done: true, value: null };
+    internal.pos = pos + internal.stride;
+    return { done: false, value: (0, internal.construct)(pos, internal.ast) };
+  }
+
+  [Symbol.iterator]() {
+    return this;
+  }
+}
+
+/**
+ * Iterator over keys of a `NodeArray`. Returned by `keys` method.
+ */
+class NodeArrayKeysIterator {
+  #internal;
+
+  constructor(proxy) {
+    const internal = getInternalFromProxy(proxy);
+    this.#internal = { index: 0, length: internal.length };
+  }
+
+  next() {
+    const internal = this.#internal,
+      { index } = internal;
+    if (index === internal.length) return { done: true, value: null };
+    internal.index = index + 1;
+    return { done: false, value: index };
+  }
+
+  [Symbol.iterator]() {
+    return this;
+  }
+}
+
+/**
+ * Iterator over values of a `NodeArray`. Returned by `entries` method.
+ */
+class NodeArrayEntriesIterator {
+  #internal;
+
+  constructor(proxy) {
+    const internal = getInternalFromProxy(proxy);
+
+    this.#internal = {
+      index: 0,
+      length: internal.length,
+      pos: internal.pos,
+      ast: internal.ast,
+      construct: internal.construct,
+      stride: internal.stride,
+    };
+  }
+
+  next() {
+    const internal = this.#internal,
+      { index } = internal;
+    if (index === internal.length) return { done: true, value: null };
+    internal.index = index + 1;
+    return {
+      done: false,
+      value: [index, (0, internal.construct)(internal.pos + index * internal.stride, internal.ast)],
+    };
+  }
+
+  [Symbol.iterator]() {
+    return this;
+  }
+}
+
+// Class used for `[Symbol.for('nodejs.util.inspect.custom')]` method (for `console.log`).
+const DebugNodeArray = class NodeArray extends Array {};
+
+// Proxy handlers.
+//
+// Every `NodeArray` returned to user is wrapped in a `Proxy`, using these handlers.
+// They lazily deserialize array elements upon access, and block mutation of array elements / `length`.
+const PROXY_HANDLERS = {
+  // Return `true` for indexes which are in bounds.
+  // e.g. `'0' in arr`.
+  has(arr, key) {
+    const index = toIndex(key);
+    if (index !== null) return index < getLength(arr);
+    return Reflect.has(arr, key);
+  },
+
+  // Get elements and length.
+  get(arr, key) {
+    // Methods of `NodeArray` are called with `this` being the proxy, rather than the `NodeArray` itself.
+    // They can "unwrap" the proxy by getting `this[ARRAY]`.
+    if (key === ARRAY) return arr;
+    if (key === "length") return getLength(arr);
+    const index = toIndex(key);
+    if (index !== null) return getElement(arr, index);
+
+    return Reflect.get(arr, key);
+  },
+
+  // Get descriptors for elements and length.
+  getOwnPropertyDescriptor(arr, key) {
+    if (key === "length") {
+      // Cannot return `writable: false` unfortunately
+      return { value: getLength(arr), writable: true, enumerable: false, configurable: false };
+    }
+
+    const index = toIndex(key);
+    if (index !== null) {
+      const value = getElement(arr, index);
+      if (value === void 0) return void 0;
+      // Cannot return `configurable: false` unfortunately
+      return { value, writable: false, enumerable: true, configurable: true };
+    }
+
+    return Reflect.getOwnPropertyDescriptor(arr, key);
+  },
+
+  // Prevent setting `length` or entries.
+  // Catches:
+  // * `Object.defineProperty(arr, 0, {value: null})`.
+  // * `arr[1] = null`.
+  // * `arr.length = 0`.
+  // * `Object.defineProperty(arr, 'length', {value: 0})`.
+  // * Other operations which mutate entries e.g. `arr.push(123)`.
+  defineProperty(arr, key, descriptor) {
+    if (key === "length" || toIndex(key) !== null) return false;
+    return Reflect.defineProperty(arr, key, descriptor);
+  },
+
+  // Prevent deleting entries.
+  deleteProperty(arr, key) {
+    // Note: `Reflect.deleteProperty(arr, 'length')` already returns `false`
+    if (toIndex(key) !== null) return false;
+    return Reflect.deleteProperty(arr, key);
+  },
+
+  // Get keys, including element indexes.
+  ownKeys(arr) {
+    const keys = [],
+      length = getLength(arr);
+    for (let i = 0; i < length; i++) {
+      keys.push(i + "");
+    }
+    keys.push(...Reflect.ownKeys(arr));
+    return keys;
+  },
+};
+
+/**
+ * Convert key to array index, if it is a valid array index.
+ *
+ * Only strings comprising a plain integer are valid indexes.
+ * e.g. `"-1"`, `"01"`, `"0xFF"`, `"1e1"`, `"1 "` are not valid indexes.
+ * Integers >= 4294967295 are not valid indexes.
+ *
+ * @param {string|Symbol} - Key used for property lookup.
+ * @returns {number|null} - `key` converted to integer, if it's a valid array index, otherwise `null`.
+ */
+function toIndex(key) {
+  if (typeof key === "string") {
+    if (key === "0") return 0;
+    if (INDEX_REGEX.test(key)) {
+      const index = +key;
+      if (index < 4294967295) return index;
+    }
+  }
+  return null;
+}
+
+const INDEX_REGEX = /^[1-9]\d*$/;
+
+/**
+ * Convert value to integer.
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number#integer_conversion
+ *
+ * @param {*} value - Value to convert to integer.
+ * @returns {number} - Integer
+ */
+function toInt(value) {
+  value = Math.trunc(+value);
+  // `value === 0` check is to convert -0 to 0
+  if (value === 0 || Number.isNaN(value)) return 0;
+  return value;
+}