{"version":3,"file":"context.esm.js","sources":["../src/slot.ts","../src/context.ts"],"sourcesContent":["type Context = {\n  parent: Context | null;\n  slots: { [slotId: string]: any };\n}\n\n// This currentContext variable will only be used if the makeSlotClass\n// function is called, which happens only if this is the first copy of the\n// @wry/context package to be imported.\nlet currentContext: Context | null = null;\n\n// This unique internal object is used to denote the absence of a value\n// for a given Slot, and is never exposed to outside code.\nconst MISSING_VALUE: any = {};\n\nlet idCounter = 1;\n\n// Although we can't do anything about the cost of duplicated code from\n// accidentally bundling multiple copies of the @wry/context package, we can\n// avoid creating the Slot class more than once using makeSlotClass.\nconst makeSlotClass = () => class Slot<TValue> {\n  // If you have a Slot object, you can find out its slot.id, but you cannot\n  // guess the slot.id of a Slot you don't have access to, thanks to the\n  // randomized suffix.\n  public readonly id = [\n    \"slot\",\n    idCounter++,\n    Date.now(),\n    Math.random().toString(36).slice(2),\n  ].join(\":\");\n\n  public hasValue() {\n    for (let context = currentContext; context; context = context.parent) {\n      // We use the Slot object iself as a key to its value, which means the\n      // value cannot be obtained without a reference to the Slot object.\n      if (this.id in context.slots) {\n        const value = context.slots[this.id];\n        if (value === MISSING_VALUE) break;\n        if (context !== currentContext) {\n          // Cache the value in currentContext.slots so the next lookup will\n          // be faster. This caching is safe because the tree of contexts and\n          // the values of the slots are logically immutable.\n          currentContext!.slots[this.id] = value;\n        }\n        return true;\n      }\n    }\n    if (currentContext) {\n      // If a value was not found for this Slot, it's never going to be found\n      // no matter how many times we look it up, so we might as well cache\n      // the absence of the value, too.\n      currentContext.slots[this.id] = MISSING_VALUE;\n    }\n    return false;\n  }\n\n  public getValue(): TValue | undefined {\n    if (this.hasValue()) {\n      return currentContext!.slots[this.id] as TValue;\n    }\n  }\n\n  public withValue<TResult, TArgs extends any[], TThis = any>(\n    value: TValue,\n    callback: (this: TThis, ...args: TArgs) => TResult,\n    // Given the prevalence of arrow functions, specifying arguments is likely\n    // to be much more common than specifying `this`, hence this ordering:\n    args?: TArgs,\n    thisArg?: TThis,\n  ): TResult {\n    const slots = {\n      __proto__: null,\n      [this.id]: value,\n    };\n    const parent = currentContext;\n    currentContext = { parent, slots };\n    try {\n      // Function.prototype.apply allows the arguments array argument to be\n      // omitted or undefined, so args! is fine here.\n      return callback.apply(thisArg!, args!);\n    } finally {\n      currentContext = parent;\n    }\n  }\n\n  // Capture the current context and wrap a callback function so that it\n  // reestablishes the captured context when called.\n  static bind<TArgs extends any[], TResult>(\n    callback: (...args: TArgs) => TResult,\n  ) {\n    const context = currentContext;\n    return function (this: any) {\n      const saved = currentContext;\n      try {\n        currentContext = context;\n        return callback.apply(this, arguments as any);\n      } finally {\n        currentContext = saved;\n      }\n    } as typeof callback;\n  }\n\n  // Immediately run a callback function without any captured context.\n  static noContext<TResult, TArgs extends any[], TThis = any>(\n    callback: (this: TThis, ...args: TArgs) => TResult,\n    // Given the prevalence of arrow functions, specifying arguments is likely\n    // to be much more common than specifying `this`, hence this ordering:\n    args?: TArgs,\n    thisArg?: TThis,\n  ) {\n    if (currentContext) {\n      const saved = currentContext;\n      try {\n        currentContext = null;\n        // Function.prototype.apply allows the arguments array argument to be\n        // omitted or undefined, so args! is fine here.\n        return callback.apply(thisArg!, args!);\n      } finally {\n        currentContext = saved;\n      }\n    } else {\n      return callback.apply(thisArg!, args!);\n    }\n  }\n};\n\n// We store a single global implementation of the Slot class as a permanent\n// non-enumerable symbol property of the Array constructor. This obfuscation\n// does nothing to prevent access to the Slot class, but at least it ensures\n// the implementation (i.e. currentContext) cannot be tampered with, and all\n// copies of the @wry/context package (hopefully just one) will share the\n// same Slot implementation. Since the first copy of the @wry/context package\n// to be imported wins, this technique imposes a very high cost for any\n// future breaking changes to the Slot class.\nconst globalKey = \"@wry/context:Slot\";\nconst host = Array as any;\n\nexport const Slot: ReturnType<typeof makeSlotClass> = host[globalKey] || function () {\n  const Slot = makeSlotClass();\n  try {\n    Object.defineProperty(host, globalKey, {\n      value: host[globalKey] = Slot,\n      enumerable: false,\n      writable: false,\n      configurable: false,\n    });\n  } finally {\n    return Slot;\n  }\n}();\n","import { Slot } from \"./slot\";\nexport { Slot }\nexport const { bind, noContext } = Slot;\n\n// Like global.setTimeout, except the callback runs with captured context.\nexport { setTimeoutWithContext as setTimeout };\nfunction setTimeoutWithContext(callback: () => any, delay: number) {\n  return setTimeout(bind(callback), delay);\n}\n\n// Turn any generator function into an async function (using yield instead\n// of await), with context automatically preserved across yields.\nexport function asyncFromGen<TArgs extends any[], TResult>(\n  genFn: (...args: TArgs) => IterableIterator<TResult>,\n) {\n  return function (this: any) {\n    const gen = genFn.apply(this, arguments as any);\n    const boundNext = bind(gen.next);\n    const boundThrow = bind(gen.throw!);\n    type Method = typeof boundNext | typeof boundThrow;\n\n    return new Promise<TResult>((resolve, reject) => {\n      function invoke(method: Method, argument: any) {\n        try {\n          var result = method.call(gen, argument);\n        } catch (error) {\n          return reject(error);\n        }\n        const next = result.done ? resolve : invokeNext;\n        if (isPromiseLike(result.value)) {\n          result.value.then(next, result.done ? reject : invokeThrow);\n        } else {\n          next(result.value);\n        }\n      }\n      const invokeNext = (value?: any) => invoke(boundNext, value);\n      const invokeThrow = (error: any) => invoke(boundThrow, error);\n      invokeNext();\n    });\n  } as (...args: TArgs) => Promise<TResult>;\n}\n\nfunction isPromiseLike(value: any): value is PromiseLike<any> {\n  return value && typeof value.then === \"function\";\n}\n\n// If you use the fibers npm package to implement coroutines in Node.js,\n// you should call this function at least once to ensure context management\n// remains coherent across any yields.\nconst wrappedFibers: Function[] = [];\nexport function wrapYieldingFiberMethods<F extends Function>(Fiber: F): F {\n  // There can be only one implementation of Fiber per process, so this array\n  // should never grow longer than one element.\n  if (wrappedFibers.indexOf(Fiber) < 0) {\n    const wrap = (obj: any, method: string) => {\n      const fn = obj[method];\n      obj[method] = function () {\n        return noContext(fn, arguments as any, this);\n      };\n    }\n    // These methods can yield, according to\n    // https://github.com/laverdet/node-fibers/blob/ddebed9b8ae3883e57f822e2108e6943e5c8d2a8/fibers.js#L97-L100\n    wrap(Fiber, \"yield\");\n    wrap(Fiber.prototype, \"run\");\n    wrap(Fiber.prototype, \"throwInto\");\n    wrappedFibers.push(Fiber);\n  }\n  return 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