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{"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
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