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https://github.com/neovim/neovim.git
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ce8a897f98
Problem: Nvim has many Lua APIs that start callback-driven work: timers, jobs, libuv handles, and other event-loop tasks. Callers that need to sequence or cancel that work have to build their own coroutine wrappers, task bookkeeping, and cleanup rules. This makes async control flow hard to share, test, and document. Solution: Add `vim.async`, a structured-concurrency module vendored from async.nvim. It provides task handles, await/pawait helpers, sleep/timeout helpers, completion-order iteration, and semaphores on top of Nvim's event loop. The API follows the same broad model as Trio: async work has an owner, tasks are awaited explicitly, and cancellation is cooperative. Include generated vimdoc with an introductory overview and examples, a news entry, and functional tests for the new module. AI-assisted
604 lines
21 KiB
Plaintext
604 lines
21 KiB
Plaintext
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==============================================================================
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Lua module: vim.async *lua-async*
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Structured async API for Lua code that waits on event-loop work.
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`vim.async` lets Lua code wait for timers, callbacks, and other tasks without
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blocking Nvim's event loop. Async work runs inside tasks, which can pause at
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checkpoints and manage child tasks created while they are running.
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Start async work with |vim.async.run()|. Inside a task, use
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|vim.async.await()| to wait for callback-style APIs or other tasks without
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blocking the event loop. Use |vim.async.pawait()| when an awaited operation
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can fail and the current task should continue.
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Examples in this help use `local async = vim.async` for brevity.
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Example: run async work without blocking Nvim: >lua
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local async = vim.async
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async.run(function()
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vim.notify('waiting...')
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async.sleep(1000)
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vim.notify('done')
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end)
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<
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Example: await a callback-style API. Callback results are returned unchanged,
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so an error-first callback still returns `err, value`: >lua
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local async = vim.async
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async.run(function()
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local err, stat = async.await(2, fs_stat, 'notes.txt')
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if err then
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error(err, 0)
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end
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print(('notes.txt is %d bytes'):format(stat.size))
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end)
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<
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A task has two roles:
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• it is a handle that can be awaited, waited for, or closed
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• it is a scope for child tasks created while the task is running
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|vim.async.run()| creates a task. A top-level task starts immediately. A task
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created while another task is running becomes a child of that task, and its
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function starts when the parent reaches its next checkpoint. A parent task
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finishes only after its attached children finish. If a child fails without
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being handled, the parent fails and closes the remaining children.
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Use |Task:detach()| for background work that should keep running after the
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current task finishes. A detached task becomes top-level work; the original
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parent no longer waits for it or closes it.
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Awaiting a task observes that task's result; it does not attach the task to
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the awaiter or change which task owns it. Ownership is decided when the task
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is created.
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Scheduling is cooperative. When a task awaits a timer, I/O operation,
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callback, or another task, `vim.async` saves the Lua stack and returns control
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to the event loop. Other callbacks can run while the task is paused. Nothing
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interrupts synchronous Lua code in the middle of a stack frame.
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Checkpoints are the places where a task can pause, start pending child tasks,
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observe cancellation, and receive unhandled child failures. Inside a task,
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these operations are checkpoints:
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• `vim.async.await(...)`
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• `vim.async.pawait(...)`
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• `vim.async.checkpoint()`
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• successful return from the task function, which is the final checkpoint for
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child management
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Convenience APIs such as |vim.async.sleep()| and |vim.async.timeout()| can
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also checkpoint because they call checkpointing APIs internally.
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Closing a task closes its attached children. Cancellation is cooperative:
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|Task:close()| marks a task as closing, and the task observes that state at a
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checkpoint. If a task is suspended on a closable operation such as a timer or
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child task, `vim.async` closes that operation before reporting the
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cancellation.
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Use |vim.async.await()| inside a task to suspend until work completes. It
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accepts a task, a callback-taking function, or an argument position plus a
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callback-taking function. `await(task)` returns the task result or raises the
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task failure. |vim.async.pawait()| is the async counterpart to `pcall()` for
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recoverable awaited-operation failures; it returns `ok, ...` instead of
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failing the current task for that awaited operation. It does not suppress
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cancellation or a failure already pending on the current task.
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From synchronous code, use |Task:wait()| or |Task:pwait()| to pump the event
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loop until the task completes. Use |Task:on_complete()| to observe completion
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without blocking.
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Coordination helpers work with task handles. |vim.async.iter()| yields
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completed task handles in completion order, |vim.async.timeout()| awaits a
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task with a deadline, and `vim.async.semaphore(permits)` creates a
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|vim.async.Semaphore| that limits how many tasks can hold a permit for a
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section at once.
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*vim.async.Closable*
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Fields: ~
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• {close} (`fun(self, callback?: fun())`)
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• {is_closing}? (`fun(self): boolean`)
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*vim.async.Semaphore*
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A semaphore manages an internal permit counter. |Semaphore:acquire()|
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consumes one permit and |Semaphore:release()| returns one permit. If no
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permits are available, `acquire()` suspends the current task until another
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task releases one.
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The preferred way to use a Semaphore is with the `with()` method, which
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automatically acquires and releases the semaphore around a function call.
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This is useful for limiting sections that start external work and then
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await it, such as file reads, requests, or subprocesses. >lua
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local async = vim.async
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async.run(function()
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local limit = async.semaphore(4)
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local tasks = {}
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for _, path in ipairs(paths) do
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table.insert(tasks, async.run(function()
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return limit:with(function()
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return read_file(path)
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end)
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end))
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end
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local next_task = async.iter(tasks)
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while true do
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local task = next_task()
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if task == nil then
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break
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end
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async.await(task)
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end
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end)
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<
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Fields: ~
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• {acquire} (`fun(self: vim.async.Semaphore)`) See
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|Semaphore:acquire()|.
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• {release} (`fun(self: vim.async.Semaphore)`) See
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|Semaphore:release()|.
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• {with} (`fun(self: vim.async.Semaphore, fn: async fun(): R...): R...`)
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See |Semaphore:with()|.
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*vim.async.Task*
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Extends: |vim.async.Closable|
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A coroutine-backed async operation and concurrency scope.
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Use |vim.async.run()| to create tasks. A task may be awaited by more than
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one waiter. When a task is created inside another task, it is attached to
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that parent and becomes part of the parent's concurrency scope.
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Fields: ~
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• {close} (`fun(self: vim.async.Task, callback: fun()?)`) See
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|Task:close()|.
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• {completed} (`fun(self: vim.async.Task): boolean`) See
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|Task:completed()|.
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• {detach} (`fun(self: vim.async.Task): vim.async.Task<R>`) See
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|Task:detach()|.
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• {name}? (`string`) Name of the task
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• {on_complete} (`fun(self: vim.async.Task, callback: fun(err?: any, ...: R...)): fun()`)
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See |Task:on_complete()|.
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• {pwait} (`fun(self: vim.async.Task, timeout: integer?): boolean, R...`)
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See |Task:pwait()|.
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• {raise_on_error} (`fun(self: vim.async.Task): vim.async.Task<R>`) See
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|Task:raise_on_error()|.
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• {status} (`fun(self: vim.async.Task): "running"|"awaiting"|"normal"|"completed"`)
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See |Task:status()|.
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• {traceback} (`fun(self: vim.async.Task, msg: string?, level: integer?): string`)
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See |Task:traceback()|.
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• {wait} (`fun(self: vim.async.Task, timeout: integer?): R...`)
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See |Task:wait()|.
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await({...}) *vim.async.await()*
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Suspend the current task until an awaitable completes.
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Accepts a task, a callback-taking function, or an argument position plus a
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callback-taking function. Raises awaited errors and current task-control
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errors.
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The callback forms return callback arguments unchanged: >lua
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local async = vim.async
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async.run(function()
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local err, stat = async.await(2, vim.uv.fs_stat, 'notes.txt')
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if err then
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error(err, 0)
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end
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print(stat.size)
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end)
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<
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If a callback API starts cancellable work, return a closable handle from
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the await callback. |Task:close()| will close that handle if cancellation
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arrives while the task is suspended there. >lua
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local async = vim.async
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async.run(function()
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local lines = async.await(function(done)
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return start_read_lines('notes.txt', done)
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end)
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render(lines)
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end)
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<
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Parameters: ~
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• {...} (`any`) see overloads
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Overloads: ~
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• `async fun(func: (fun(callback: fun(...: R...)): vim.async.Closable?)): R...`
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• `async fun(argc: integer, func: (fun(...: T..., callback: fun(...: R...)): vim.async.Closable?), ...: T...): R...`
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• `async fun(task: vim.async.Task<R>): R...`
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Return: ~
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(`R...`)
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checkpoint() *vim.async.checkpoint()*
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Start pending child tasks and deliver pending cancellation or task failure
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from the current task.
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This does not yield to the event loop.
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Use this after cleanup code that catches an async failure or close signal,
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so persistent task state is delivered again before normal execution
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continues. >lua
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local ok, err = pcall(cleanup_sensitive_work)
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cleanup_resources()
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vim.async.checkpoint()
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if not ok then
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error(err, 0)
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end
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<
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is_closing() *vim.async.is_closing()*
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Returns true if the current task has been closed.
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Can be used in an async function to do cleanup when a task is closing. >lua
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while not vim.async.is_closing() do
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poll_once()
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vim.async.sleep(1000)
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end
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<
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Return: ~
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(`boolean`)
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iter({tasks}) *vim.async.iter()*
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Iterate completed tasks in completion order.
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The iterator yields task handles, not task results. Use
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|vim.async.await()| or |vim.async.pawait()| to retrieve each result. The
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tasks are observed in the order they complete, regardless of the order in
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the input list. >lua
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local async = vim.async
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async.run(function()
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local tasks = {
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async.run(function() return 'cache', read_cache() end):detach(),
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async.run(function() return 'disk', read_file() end):detach(),
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}
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for task in async.iter(tasks) do
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local ok, source, text = async.pawait(task)
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if ok then
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for _, other in ipairs(tasks) do
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if other ~= task then
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other:close()
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end
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end
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print(('loaded from %s'):format(source))
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return text
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end
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end
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end)
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<
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If code must support PUC Lua 5.1, use the direct-call form instead of a
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generic `for` loop. The iterator may need to suspend while waiting for the
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next completed task, and PUC Lua 5.1 cannot yield from a generic-for
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iterator call. >lua
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local next_task = async.iter(tasks)
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while true do
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local task = next_task()
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if task == nil then
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break
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end
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async.await(task)
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end
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<
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Parameters: ~
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• {tasks} (`vim.async.Task<R>[]`) A list of tasks to wait for and
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iterate over.
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Return: ~
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(`async fun(): vim.async.Task<R>?`) iterator that yields each
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completed task.
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pawait({...}) *vim.async.pawait()*
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Protected await.
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Async counterpart to `pcall()`. Accepts the same forms as
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|vim.async.await()|, but returns a leading `ok` boolean for
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awaited-operation failures.
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Use this when the awaited task or operation is allowed to fail and the
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current task should continue. Cancellation or already pending failure from
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the current task is not protected. >lua
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local async = vim.async
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async.run(function()
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local ok, text_or_err = async.pawait(async.run(read_file, 'notes.txt'))
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if not ok then
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text_or_err = ''
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end
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show_buffer(text_or_err)
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end)
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<
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Parameters: ~
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• {...} (`any`) see overloads
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Overloads: ~
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• `async fun(func: (fun(callback: fun(...: R...)): vim.async.Closable?)): boolean, R...`
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• `async fun(argc: integer, func: (fun(...: T..., callback: fun(...: R...)): vim.async.Closable?), ...: T...): boolean, R...`
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• `async fun(task: vim.async.Task<R>): boolean, R...`
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Return (multiple): ~
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(`boolean`) ok
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(`R...`) ... result or error
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(`_overload`) true
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(`R...`)
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(`_overload`) false
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(`any`)
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run({func}, {...}) *vim.async.run()*
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Create a task from an async function.
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Top-level tasks start immediately. Child tasks are attached immediately
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and first run when their parent reaches a checkpoint.
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Creating a task decides ownership. Awaiting the task later only observes
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its result; it does not attach the task to the awaiter. >lua
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local async = vim.async
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async.run(function()
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local child = async.run(function()
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return read_file('notes.txt')
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end)
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local text = async.await(child)
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show_buffer(text)
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end)
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<
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A task created from synchronous code is top-level: >lua
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local task = vim.async.run(function()
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vim.async.sleep(100)
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return 'done'
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end)
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print(task:wait())
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<
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Parameters: ~
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• {func} (`async fun(...: T...): R...`)
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• {...} (`T...`) Arguments to pass to the function
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Overloads: ~
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• `fun(name: string, func: async fun(...: T...), ...: T...): vim.async.Task<R...>`
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Return: ~
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(`vim.async.Task<R...>`)
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Semaphore:acquire() *Semaphore:acquire()*
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Acquire a semaphore permit.
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If the internal counter is greater than zero, decrement it by `1` and
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return immediately. If it is `0`, wait until |Semaphore:release()| is
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called.
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Semaphore:release() *Semaphore:release()*
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Release a semaphore permit.
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Increments the internal counter by `1` and can wake a task waiting in
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|Semaphore:acquire()|.
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Calling this more times than permits were acquired raises an error.
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Semaphore:with({fn}) *Semaphore:with()*
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Executes a function while holding one semaphore permit.
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This acquires the semaphore before running the function and releases it
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after the function completes, even if it errors or the current task is
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closed.
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Parameters: ~
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• {fn} (`async fun(): R...`) Function to execute within the semaphore's
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context.
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Return: ~
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(`R...`) Result(s) of the executed function.
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sleep({duration}) *vim.async.sleep()*
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Asynchronously sleep for a given duration.
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Suspends the current task for the given duration without blocking the
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event loop. After the delay and timer cleanup complete, `sleep()` returns
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to its caller through the runtime's `schedule` hook. >lua
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vim.async.run(function()
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vim.async.sleep(100)
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vim.notify('resumed later')
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end)
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<
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Parameters: ~
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• {duration} (`integer`) ms
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Task:close({callback}) *Task:close()*
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Request cooperative close for the task and all of its children.
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The optional callback observes task completion and may run immediately if
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the task has already completed.
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Closing is cooperative. The task observes the close request at a
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checkpoint such as |vim.async.await()| or |vim.async.checkpoint()|. If the
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task is suspended on an owned closable operation, that operation is closed
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before the task reports `"closed"`.
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Parameters: ~
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• {callback} (`fun()?`)
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Task:completed() *Task:completed()*
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Returns whether the Task has completed.
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Return: ~
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(`boolean`)
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Task:detach() *Task:detach()*
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Detach a task from its parent.
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The task becomes a top-level task. If it was waiting for a parent
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checkpoint, it is scheduled to start.
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Use this for background work that should not be cancelled when the current
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task finishes. Detached task failures no longer fail the original parent,
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so observe them explicitly with |Task:on_complete()|, |Task:wait()|, or
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|vim.async.await()|. >lua
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vim.async.run(function()
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while true do
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refresh_index()
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vim.async.sleep(1000)
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end
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end):detach()
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<
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Return: ~
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(`vim.async.Task<R>`)
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Task:on_complete({callback}) *Task:on_complete()*
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Add a callback to be run when the Task has completed.
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If the Task is already done when this method is called, the callback is
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called immediately with the results.
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This only observes completion. It does not start a pending task.
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Parameters: ~
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• {callback} (`fun(err?: any, ...: R...)`)
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Return: ~
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(`fun()`) unsubscribe
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Task:pwait({timeout}) *Task:pwait()*
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Protected-call version of |Task:wait()|.
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Equivalent to `pcall(task.wait, task, timeout)`. >lua
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local ok, result_or_err = task:pwait(1000)
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if not ok then
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vim.notify(tostring(result_or_err), vim.log.levels.ERROR)
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end
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<
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Parameters: ~
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• {timeout} (`integer?`)
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Return (multiple): ~
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(`boolean`)
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(`R...`)
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Task:raise_on_error() *Task:raise_on_error()*
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Raise this task's error when it completes.
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Use this for detached or top-level fire-and-forget tasks whose completion
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will not otherwise be observed. Attached task errors already propagate to
|
|
their parent.
|
|
|
|
Detached tasks do not raise errors automatically. Detaching changes
|
|
ownership only; their completion can still be handled with
|
|
|vim.async.await()|, |Task:wait()|, |Task:pwait()|, or
|
|
|Task:on_complete()|.
|
|
|
|
Return: ~
|
|
(`vim.async.Task<R>`) self
|
|
|
|
Task:status() *Task:status()*
|
|
Returns the status of the task:
|
|
• `"running"`: task is currently executing Lua code
|
|
• `"normal"`: task is active but another coroutine is running
|
|
• `"awaiting"`: task is suspended at a checkpoint or waiting for children
|
|
• `"completed"`: task and all attached children have completed
|
|
|
|
Return: ~
|
|
(`"running"|"awaiting"|"normal"|"completed"`)
|
|
|
|
Task:traceback({msg}, {level}) *Task:traceback()*
|
|
Get the traceback of a task when it is not active. Will also get the
|
|
traceback of nested tasks.
|
|
|
|
Parameters: ~
|
|
• {msg} (`string?`)
|
|
• {level} (`integer?`)
|
|
|
|
Return: ~
|
|
(`string`) traceback
|
|
|
|
Task:wait({timeout}) *Task:wait()*
|
|
Synchronously wait for the Task to complete.
|
|
|
|
If a timeout is provided, waits for the given time in milliseconds before
|
|
failing with `"timeout"`. With no timeout, waits indefinitely.
|
|
|
|
This is for synchronous code. Inside a task, prefer |vim.async.await()| so
|
|
the current task suspends instead of pumping the event loop itself. >lua
|
|
local result = task:wait(10) -- wait for 10ms or raise "timeout"
|
|
|
|
local result = task:wait() -- wait indefinitely
|
|
<
|
|
|
|
Parameters: ~
|
|
• {timeout} (`integer?`)
|
|
|
|
Return: ~
|
|
(`R...`)
|
|
|
|
timeout({duration}, {task}) *vim.async.timeout()*
|
|
Await a task with a timeout.
|
|
|
|
If the task completes first, returns or raises the task result as
|
|
|vim.async.await()| would. If the deadline wins, closes the task and
|
|
raises `"timeout"` after the target task finishes cancellation cleanup. >lua
|
|
local async = vim.async
|
|
|
|
async.run(function()
|
|
local task = async.run(read_file, 'notes.txt')
|
|
local text = async.timeout(5000, task)
|
|
show_buffer(text)
|
|
end)
|
|
<
|
|
|
|
Parameters: ~
|
|
• {duration} (`integer`) Timeout duration in milliseconds
|
|
• {task} (`vim.async.Task<R>`)
|
|
|
|
Return: ~
|
|
(`R...`)
|
|
|
|
wrap({argc}, {func}) *vim.async.wrap()*
|
|
Create an async function from a callback-style function.
|
|
|
|
The callback is inserted at argument position `argc`. If `func` returns a
|
|
closable handle, it is closed when the awaiting task is cancelled.
|
|
|
|
This is a reusable wrapper around |vim.async.await()|. Use it when the
|
|
same callback API is awaited from more than one place. >lua
|
|
local async = vim.async
|
|
local fs_stat = async.wrap(2, vim.uv.fs_stat)
|
|
|
|
async.run(function()
|
|
local err, stat = fs_stat(vim.api.nvim_buf_get_name(0))
|
|
if not err and stat then
|
|
print(stat.size)
|
|
end
|
|
end)
|
|
<
|
|
|
|
Parameters: ~
|
|
• {argc} (`integer`)
|
|
• {func} (`fun(...: T..., callback: fun(...: R...)): vim.async.Closable?`)
|
|
|
|
Return: ~
|
|
(`async fun(...: T...): R...`)
|
|
|
|
|
|
vim:tw=78:ts=8:sw=4:sts=4:et:ft=help:norl:
|