fun

README

fun -- Go Generic Functions and Tools

fun is a simple, well tested, zero-dependency, collection of packages with generic function, tools, patterns, and the kind of thing you could write one-offs for but shouldn't.

Packages:

• erc (error collecting.)
• itertool (iterator tools.)
• pubsub (message broker and queues.)
• set (generic ordered and unordered sets.)
• seq (generic linked lists.)
• srv (service orchestration and management framework.)
• adt (strongly atomic data types and operations.)

For more information, see the documentation, but of general interest:

• In itertools and with fun.Iterator, an iterator framework and tools for interacting with iterators and generators.
• In pubsub, a channel-based message broker (for one-to-many channel patterns), with several backend patterns for dealing with load-shedding and message distribution patterns.
• In erc, an error collector implementation for threadsafe error aggregation and introspection, particularly in worker-pool, applications.
• In set, a Set type, with ordered and unordered implementations.
• Queue and Deque implementations (in pubsub) that provide thread-safe linked-list based implementations and Wait methods to block until new items added.
• In seq, general purpose linked list implementations, with a healthy feature set and flexible interface.
• In srv, a service orchestration toolkit and lifecycle tools.
• In adt, a collection of Atomic/Pool/Map operations that use generics to provide strongly typed interfaces for common operations.

Contributions welcome, the general goals of the project:

• superior API ergonomics.
• great high-level abstractions.
• obvious and clear implementations.
• minimal dependencies.

Have fun!

Documentation

Overview

Package fun is a zero-dependency collection of tools and idoms that takes advantage of generics. Iterators, error handling, a native-feeling Set type, and a simple pub-sub framework for distributing messages in fan-out patterns.

Index

• Variables
• func Check(fn func()) (err error)
• func Contains[T comparable](item T, slice []T) bool
• func Count[T any](ctx context.Context, iter Iterator[T]) int
• func Ignore[T any](fn func(T) error, arg T)
• func IgnoreMust[T any, O any](fn func(T) (O, error), arg T) O
• func Invariant(cond bool, args ...any)
• func InvariantCheck(fn func() error, args ...any)
• func InvariantMust(err error, args ...any)
• func Is[T any](in any) bool
• func IsInvariantViolation(r any) bool
• func IsWrapped[T any](in T) bool
• func IsZero[T comparable](in T) bool
• func IterateOne[T any](ctx context.Context, iter Iterator[T]) (T, error)
• func IterateOneBlocking[T any](iter Iterator[T]) (T, error)
• func Must[T any](arg T, err error) T
• func MustBeOk[T any](out T, ok bool) T
• func Observe[T any](ctx context.Context, iter Iterator[T], fn Observer[T]) (err error)
• func Protect[I any, O any](fn func(I) (O, error)) func(I) (O, error)
• func ReadOne[T any](ctx context.Context, ch <-chan T) (T, error)
• func Safe[T any](fn func() T) (out T, err error)
• func Unwind[T any](in T) []T
• func Unwrap[T any](in T) T
• func WhenCall(cond bool, op func())
• func WhenDo[T any](cond bool, op func() T) T
• func Zero[T any](T) T
• func ZeroOf[T any]() T
• func ZeroWhenNil[T any](val any) T
• type Iterator
  • func Filter[T any](iter Iterator[T], check func(T) bool) Iterator[T]
  • func Generator[T any](op func(context.Context) (T, error)) Iterator[T]
  • func PairKeys[K comparable, V any](iter Iterator[Pair[K, V]]) Iterator[K]
  • func PairValues[K comparable, V any](iter Iterator[Pair[K, V]]) Iterator[V]
  • func Transform[I, O any](iter Iterator[I], op func(in I) (O, error)) Iterator[O]
• type Map
  • func Mapify[K comparable, V any](in map[K]V) Map[K, V]
  • func (m Map[K, V]) Add(k K, v V)
  • func (m Map[K, V]) AddPair(p Pair[K, V])
  • func (m Map[K, V]) Append(pairs ...Pair[K, V])
  • func (m Map[K, V]) Consume(ctx context.Context, iter Iterator[Pair[K, V]])
  • func (m Map[K, V]) ConsumeMap(in Map[K, V])
  • func (m Map[K, V]) ConsumeSlice(in []V, keyf func(V) K)
  • func (m Map[K, V]) ConsumeValues(ctx context.Context, iter Iterator[V], keyf func(V) K)
  • func (m Map[K, V]) Extend(pairs Pairs[K, V])
  • func (m Map[K, V]) Iterator() Iterator[Pair[K, V]]
  • func (m Map[K, V]) Keys() Iterator[K]
  • func (m Map[K, V]) Len() int
  • func (m Map[K, V]) Pairs() Pairs[K, V]
  • func (m Map[K, V]) Values() Iterator[V]
• type Observer
  • func (of Observer[T]) Safe(in T) (err error)
  • func (of Observer[T]) Wait(in T) WaitFunc
  • func (of Observer[T]) Worker(in T) WorkerFunc
• type Pair
  • func MakePair[K comparable, V any](k K, v V) Pair[K, V]
• type Pairs
  • func MakePairs[K comparable, V any](in map[K]V) Pairs[K, V]
  • func (p *Pairs[K, V]) Add(k K, v V)
  • func (p *Pairs[K, V]) AddPair(pair Pair[K, V])
  • func (p Pairs[K, V]) Append(new ...Pair[K, V]) Pairs[K, V]
  • func (p *Pairs[K, V]) Consume(ctx context.Context, iter Iterator[Pair[K, V]])
  • func (p *Pairs[K, V]) ConsumeMap(in map[K]V)
  • func (p *Pairs[K, V]) ConsumeSlice(in []V, keyf func(V) K)
  • func (p *Pairs[K, V]) ConsumeValues(ctx context.Context, iter Iterator[V], keyf func(V) K)
  • func (p Pairs[K, V]) Iterator() Iterator[Pair[K, V]]
  • func (p Pairs[K, V]) Keys() Iterator[K]
  • func (p Pairs[K, V]) Map() map[K]V
  • func (p Pairs[K, V]) MarshalJSON() ([]byte, error)
  • func (p *Pairs[K, V]) UnmarshalJSON(in []byte) error
  • func (p Pairs[K, V]) Values() Iterator[V]
• type Send
  • func Blocking[T any](ch chan<- T) Send[T]
  • func NonBlocking[T any](ch chan<- T) Send[T]
  • func (sm Send[T]) Check(ctx context.Context, it T) bool
  • func (sm Send[T]) Ignore(ctx context.Context, it T)
  • func (sm Send[T]) Send(ctx context.Context, it T) (err error)
• type WaitFunc
  • func WaitBlocking(fn func()) WaitFunc
  • func WaitBlockingObserve[T any](observe func(T), wait func() T) WaitFunc
  • func WaitChannel[T any](ch <-chan T) WaitFunc
  • func WaitContext(ctx context.Context) WaitFunc
  • func WaitForGroup(wg *sync.WaitGroup) WaitFunc
  • func WaitMerge(ctx context.Context, iter Iterator[WaitFunc]) WaitFunc
  • func WaitObserve[T any](observe Observer[T], ch <-chan T) WaitFunc
  • func WaitObserveAll[T any](observe Observer[T], ch <-chan T) WaitFunc
  • func WaitObserveAllCtx[T any](observe func(context.Context, T), ch <-chan T) WaitFunc
  • func (wf WaitFunc) Add(ctx context.Context, wg *WaitGroup)
  • func (wf WaitFunc) Block()
  • func (wf WaitFunc) BlockSignal() <-chan struct{}
  • func (wf WaitFunc) Check() WorkerFunc
  • func (wf WaitFunc) Run(ctx context.Context)
  • func (wf WaitFunc) Safe() WorkerFunc
  • func (wf WaitFunc) Signal(ctx context.Context) <-chan struct{}
  • func (wf WaitFunc) WithTimeout(timeout time.Duration)
  • func (wf WaitFunc) WithTimeoutSignal(timeout time.Duration) <-chan struct{}
  • func (wf WaitFunc) Worker() WorkerFunc
• type WaitGroup
  • func (wg *WaitGroup) Add(num int)
  • func (wg *WaitGroup) Done()
  • func (wg *WaitGroup) IsDone() bool
  • func (wg *WaitGroup) Num() int
  • func (wg *WaitGroup) Wait(ctx context.Context)
• type WorkerFunc
  • func ObserveWorker[T any](iter Iterator[T], fn Observer[T]) WorkerFunc
  • func (wf WorkerFunc) Add(ctx context.Context, wg *WaitGroup, ob Observer[error])
  • func (wf WorkerFunc) Background(ctx context.Context, ob Observer[error])
  • func (wf WorkerFunc) Block() error
  • func (wf WorkerFunc) MustWait() WaitFunc
  • func (wf WorkerFunc) Observe(ctx context.Context, ob Observer[error])
  • func (wf WorkerFunc) ObserveWait(ob Observer[error]) WaitFunc
  • func (wf WorkerFunc) Run(ctx context.Context) error
  • func (wf WorkerFunc) Safe(ctx context.Context) (err error)
  • func (wf WorkerFunc) Singal(ctx context.Context) <-chan error
  • func (wf WorkerFunc) WithTimeout(timeout time.Duration) error

Variables

var (
	// ErrInvariantViolation is the root error of the error object that is
	// the content of all panics produced by the Invariant helper.
	ErrInvariantViolation = errors.New("invariant violation")
	// ErrRecoveredPanic is at the root of any error returned by a
	// function in the fun package that recovers from a panic.
	ErrRecoveredPanic = errors.New("recovered panic")
)

var ErrSkippedNonBlockingSend = errors.New("skipped non-blocking send")

ErrSkippedNonBlockingSend is returned when sending into a channel, in a non-blocking context, when the channel was blocking and the send was therefore skipped.

Functions

func Check

func Check(fn func()) (err error)

Check, like Safe, runs a function without arguments that does not produce an error, and, if the function panics, converts it into an error.

func Contains

func Contains[T comparable](item T, slice []T) bool

Contain returns true if an element of the slice is equal to the item.

func Count

func Count[T any](ctx context.Context, iter Iterator[T]) int

Count returns the number of items observed by the iterator. Callers should still manually call Close on the iterator.

func Ignore

func Ignore[T any](fn func(T) error, arg T)

Ignore runs a function that takes an arbitrary argument and ignores the error and swallows any panic. This is a risky move: usually functions panic for a reason, but for certain invariants this may be useful.

Be aware, that while Ignore will recover from any panics, defers within the ignored function will not run unless there is a call to recover *before* the defer.

func IgnoreMust

func IgnoreMust[T any, O any](fn func(T) (O, error), arg T) O

IgnoreMust runs a function that takes an arbitrary argument and ignores the error and swallows any panic, returning the output of the function, likely a Zero value, in the case of an error. This is a risky move: usually functions panic for a reason, but for certain invariants this may be useful.

Be aware, that while Ignore will recover from any panics, defers within the ignored function will not run unless there is a call to recover *before* the defer.

func Invariant

func Invariant(cond bool, args ...any)

Invariant panics if the condition is false Invariant panics, passing an error that is rooted by ErrInvariantViolation.

func InvariantCheck

func InvariantCheck(fn func() error, args ...any)

InvariantCheck calls the function and if it returns an error panics with an ErrInvariantViolation error, wrapped with the error of the function, and any annotation arguments.

func InvariantMust

func InvariantMust(err error, args ...any)

InvariantMust raises an invariant error if the error is not nil. The content of the panic is both--via wrapping--an ErrInvariantViolation and the error itself.

func Is

func Is[T any](in any) bool

Is a generic version of `errors.Is` that takes advantage of the Unwrap function, and is useful for checking if an object of an interface type is or wraps an implementation of the type parameter.

func IsInvariantViolation

func IsInvariantViolation(r any) bool

IsInvariantViolation returns true if the argument is or resolves to ErrInvariantViolation.

func IsWrapped

func IsWrapped[T any](in T) bool

IsWrapped returns true if the input value wraps another value of the same type.

func IsZero

func IsZero[T comparable](in T) bool

IsZero returns true if the input value compares "true" to the zero value for the type of the argument. If the type implements an IsZero() method (e.g. time.Time), then IsZero returns that value, otherwise, IsZero constructs a zero valued object of type T and compares the input value to the zero value.

func IterateOne

func IterateOne[T any](ctx context.Context, iter Iterator[T]) (T, error)

IterateOne, like ReadOne reads one value from the iterator, and returns it. The error values are either a context cancelation error if the context is canceled, or io.EOF if there are no elements in the iterator. The semantics of fun.IterateOne and fun.ReadOne are the same.

IterateOne does not provide atomic exclusion if multiple calls to the iterator or IterateOne happen concurrently; however, the adt.NewIterator wrapper, and most of the iterator implementations provided by the fun package, provide a special case which *does* allow for safe and atomic concurrent use with fun.IterateOne.

func IterateOneBlocking

func IterateOneBlocking[T any](iter Iterator[T]) (T, error)

IterateOneBlocking has the same semantics as IterateOne except it uses a blocking context, and if the iterator is blocking and there are no more items, IterateOneBlocking will never return. Use with caution, and in situations where you understand the iterator's implementation.

func Must

func Must[T any](arg T, err error) T

Must wraps a function that returns a value and an error, and converts the error to a panic.

func MustBeOk

func MustBeOk[T any](out T, ok bool) T

MustBeOk raises an invariant violation if the ok value is false, and returns the first value if the second value is ok. Useful as in:

out := fun.MustBeOk(func() (string ok) { return "hello world", true })

func Observe

func Observe[T any](ctx context.Context, iter Iterator[T], fn Observer[T]) (err error)

Observe processes an iterator calling the observer function for every element in the iterator and retruning when the iterator is exhausted. Take care to ensure that the Observe function does not block.

The error returned captures any panics encountered as an error, as well as the output of the Close() operation.

func Protect

func Protect[I any, O any](fn func(I) (O, error)) func(I) (O, error)

Protect wraps a function with a panic handler, that will parse and attach the content of the pantic to the error output (while maintaining the functions orginial error.) All handled panics will be annotated with fun.ErrRecoveredPanic.

func ReadOne

func ReadOne[T any](ctx context.Context, ch <-chan T) (T, error)

ReadOnce reads one item from the channel, and returns it. ReadOne returns early if the context is canceled (ctx.Err()) or the channel is closed (io.EOF).

func Safe

func Safe[T any](fn func() T) (out T, err error)

Safe runs a function with a panic handler that converts the panic to an error.

func Unwind

func Unwind[T any](in T) []T

Unwind uses the Unwrap operation to build a list of the "wrapped" objects.

func Unwrap

func Unwrap[T any](in T) T

Unwrap is a generic equivalent of the `errors.Unwrap()` function for any type that implements an `Unwrap() T` method. useful in combination with Is.

func WhenCall

func WhenCall(cond bool, op func())

WhenCall runs a function when condition is true, and is a noop otherwise.

func WhenDo

func WhenDo[T any](cond bool, op func() T) T

WhenDo calls the function when the condition is true, and returns the result, or if the condition is false, the operation is a noop, and returns zero-value for the type.

func Zero

func Zero[T any](T) T

Zero returns the zero-value for the type T of the input argument.

func ZeroOf

func ZeroOf[T any]() T

ZeroOf returns the zero-value for the type T specified as an argument.

func ZeroWhenNil

func ZeroWhenNil[T any](val any) T

ZeroWhenNil takes a value of any type, and if that value is nil, returns the zero value of the specified type. Otherwise, ZeroWhenNil coerces the value into T and returns it. If the input value does not match the output type of the function, ZeroWhenNil panics with an ErrInvariantViolation.

Types

type Iterator

type Iterator[T any] interface {
	Next(context.Context) bool
	Close() error
	Value() T
}

Iterator provides a safe, context-respecting iterator paradigm for iterable objects, along with a set of consumer functions and basic implementations.

The itertool package provides a number of tools and paradigms for creating and processing Iterator objects, including Generators, Map and Reduce as well as Split and Merge to combine or divide iterators.

In general, Iterators cannot be safe for access from multiple concurrent goroutines, because it is impossible to synchronize calls to Next() and Value(); however, itertool.Range() and itertool.Split() provide support for these workloads.

func Filter

func Filter[T any](iter Iterator[T], check func(T) bool) Iterator[T]

Filter passes every item in the input iterator and, if the check function returns true propogates it to the output iterator. There is no buffering, and check functions should return quickly. For more advanced use, consider using itertool.Map()

func Generator

func Generator[T any](op func(context.Context) (T, error)) Iterator[T]

Generator creates an iterator that produces new values, using the generator function provided. This implementation does not create any background go routines, and the iterator will produce values until the function returns an error or the Close() method is called. Any non-nil error returned by the generator function is propagated to the close method, as long as it is not a context cancellation error or an io.EOF error.

func PairKeys

func PairKeys[K comparable, V any](iter Iterator[Pair[K, V]]) Iterator[K]

PairKeys converts an iterator of Pairs to an iterator of its keys.

func PairValues

func PairValues[K comparable, V any](iter Iterator[Pair[K, V]]) Iterator[V]

PairValues converts an iterator of pairs to an iterator of its values.

func Transform

func Transform[I, O any](iter Iterator[I], op func(in I) (O, error)) Iterator[O]

Transform processes the input iterator of type I into an output iterator of type O. It's implementation uses the Generator, will continue producing values as long as the input iterator produces values, the context isn't canceled, or

type Map

type Map[K comparable, V any] map[K]V

Map is just a generic type wrapper around a map, mostly for the purpose of being able to interact with Pair[K,V] objects and Iterators.

func Mapify

func Mapify[K comparable, V any](in map[K]V) Map[K, V]

Mapify provides a constructor that will produce a fun.Map without specifying types.

func (Map[K, V]) Add

func (m Map[K, V]) Add(k K, v V)

Add adds a key value pair directly to the map.

func (Map[K, V]) AddPair

func (m Map[K, V]) AddPair(p Pair[K, V])

AddPair adds a Pair object to the map.

func (Map[K, V]) Append

func (m Map[K, V]) Append(pairs ...Pair[K, V])

Append adds a sequence of Pair objects to the map.

func (Map[K, V]) Consume

func (m Map[K, V]) Consume(ctx context.Context, iter Iterator[Pair[K, V]])

Consume adds items to the map from an iterator of Pair objects. Existing values for K are always overwritten.

func (Map[K, V]) ConsumeMap

func (m Map[K, V]) ConsumeMap(in Map[K, V])

ConsumeMap adds all the keys from the input map the map.

func (Map[K, V]) ConsumeSlice

func (m Map[K, V]) ConsumeSlice(in []V, keyf func(V) K)

ConsumeSlice adds a slice of values to the map, using the provided function to generate the key for the value. Existing values in the map are overridden.

func (Map[K, V]) ConsumeValues

func (m Map[K, V]) ConsumeValues(ctx context.Context, iter Iterator[V], keyf func(V) K)

ConsumeValues adds items to the map, using the function to generate the keys for the values.

func (Map[K, V]) Extend

func (m Map[K, V]) Extend(pairs Pairs[K, V])

Extend adds a sequence of Pairs to the map.

func (Map[K, V]) Iterator

func (m Map[K, V]) Iterator() Iterator[Pair[K, V]]

Iterator converts a map into an iterator of fun.Pair objects. The iterator is panic-safe, and uses one go routine to track the progress through the map. As a result you should always, either exhaust the iterator, cancel the context that you pass to the iterator OR call iterator.Close().

To use this iterator the items in the map are not copied, and the iteration order is randomized following the convention in go.

Use in combination with other iterator processing tools (generators, observers, transformers, etc.) to limit the number of times a collection of data must be coppied.

func (Map[K, V]) Keys

func (m Map[K, V]) Keys() Iterator[K]

Keys provides an iterator over just the keys in the map.

func (Map[K, V]) Len

func (m Map[K, V]) Len() int

Len returns the length. It is equivalent to len(Map), but is provided for consistency.

func (Map[K, V]) Pairs

func (m Map[K, V]) Pairs() Pairs[K, V]

Pairs exports a map a Pairs object, which is an alias for a slice of Pair objects.

func (Map[K, V]) Values

func (m Map[K, V]) Values() Iterator[V]

Values provides an iterator over just the values in the map.

type Observer

type Observer[T any] func(T)

Observer describes a function that operates on a single object, but returns no output, and is used primarly for side effects, particularly around handling errors or collecting metrics. The Observer implementation here makes it possible to provide panic-safety for these kinds of functions or easily convert to other related types.

func (Observer[T]) Safe

func (of Observer[T]) Safe(in T) (err error)

Safe handles any panic encountered during the observer's execution and converts it to an error.

func (Observer[T]) Wait

func (of Observer[T]) Wait(in T) WaitFunc

Wait captures a variable and converts an Observer into a wait function that observes the value when the WaitFunc runs.

func (Observer[T]) Worker

func (of Observer[T]) Worker(in T) WorkerFunc

Worker captures a variable and returns a worker function which will, when executed, observe the input value. These worker functions, use the Safe-mode of execution.

type Pair

type Pair[K comparable, V any] struct {
	Key   K
	Value V
}

Pair represents a key-value pair. Used by the adt synchronized map implementation and the set package to handle ordered key-value pairs.

func MakePair

func MakePair[K comparable, V any](k K, v V) Pair[K, V]

MakePair constructs a pair object. This is identical to using the literal constructor but may be more ergonomic as the compiler seems to be better at inferring types in function calls over literal constructors.

type Pairs

type Pairs[K comparable, V any] []Pair[K, V]

Pairs implements a collection of key-value pairs.

func MakePairs

func MakePairs[K comparable, V any](in map[K]V) Pairs[K, V]

MakePairs converts a map type into a slice of Pair types that can be usable in a set.

func (*Pairs[K, V]) Add

func (p *Pairs[K, V]) Add(k K, v V)

Add adds a new value to the underlying slice. This may add a duplicate key.

func (*Pairs[K, V]) AddPair

func (p *Pairs[K, V]) AddPair(pair Pair[K, V])

AddPair adds a single pair to the slice of pairs.

func (Pairs[K, V]) Append

func (p Pairs[K, V]) Append(new ...Pair[K, V]) Pairs[K, V]

Append, mirroring the semantics of the built in append() function adds one or more Pair items to a Pairs slice, and returns the new slice without changing the value of the original slice:

p = p.Append(pair, pare, pear)

func (*Pairs[K, V]) Consume

func (p *Pairs[K, V]) Consume(ctx context.Context, iter Iterator[Pair[K, V]])

Consume adds items from an iterator of pairs to the current Pairs slice.

func (*Pairs[K, V]) ConsumeMap

func (p *Pairs[K, V]) ConsumeMap(in map[K]V)

ConsumeMap adds all of the items in a map to the Pairs object.

func (*Pairs[K, V]) ConsumeSlice

func (p *Pairs[K, V]) ConsumeSlice(in []V, keyf func(V) K)

ConsumeSlice adds all the values in the input slice to the Pairs object, creating the keys using the function provide.

func (*Pairs[K, V]) ConsumeValues

func (p *Pairs[K, V]) ConsumeValues(ctx context.Context, iter Iterator[V], keyf func(V) K)

ConsumeValues adds all of the values in the input iterator, generating the keys using the function provided.

func (Pairs[K, V]) Iterator

func (p Pairs[K, V]) Iterator() Iterator[Pair[K, V]]

Iterator return an iterator over each key-value pairs.

func (Pairs[K, V]) Keys

func (p Pairs[K, V]) Keys() Iterator[K]

Keys returns an iterator over only the keys in a sequence of iterator items.

func (Pairs[K, V]) Map

func (p Pairs[K, V]) Map() map[K]V

Map converts a list of pairs to the equivalent map. If there are duplicate keys in the Pairs list, only the first occurrence of the key is retained.

func (Pairs[K, V]) MarshalJSON

func (p Pairs[K, V]) MarshalJSON() ([]byte, error)

MarshalJSON produces a JSON encoding for the Pairs object by first converting it to a map and then encoding that map as JSON. The JSON serialization does not necessarily preserve the order of the pairs object.

func (*Pairs[K, V]) UnmarshalJSON

func (p *Pairs[K, V]) UnmarshalJSON(in []byte) error

UnmarshalJSON provides consistent JSON decoding for Pairs objects. It reads a JSON document into a map and converts it to pairs, and appends it to the existing Pairs objects without removing or resetting the current object.

func (Pairs[K, V]) Values

func (p Pairs[K, V]) Values() Iterator[V]

Values returns an iterator over only the values in a sequence of iterator pairs.

type Send

type Send[T any] struct {
	// contains filtered or unexported fields
}

Send provides a functional and descriptive interface for sending into channels. The only meaningful use of Send objects is via the Blocking() and NonBlocking() constructors. Invocations resemble:

ch := make(chan int)
err := fun.Blocking(ch).Send(ctx, 42)
// handle error, which is always a context cancellation error
// or io.EOF.

There are three kinds of sends: Check, which returns a boolean if the send was successful; Send(), which returns the error useful if you need to distinguish between timeouts and cancellations; and Ignore which has no response.

Send operations against closed channels return io.EOF (or false, in the case of Check) rather than panicing.

func Blocking

func Blocking[T any](ch chan<- T) Send[T]

Blocking produces a blocking Send instance. All Send/Check/Ignore operations will block until the context is canceled, the channel is canceled, or the send succeeds.

func NonBlocking

func NonBlocking[T any](ch chan<- T) Send[T]

NonBlocking produces a send instance that performs a non-blocking send.

The Send() method, for non-blocking sends, will return ErrSkipedNonBlockingSend if the channel was full and the object was not sent.

func (Send[T]) Check

func (sm Send[T]) Check(ctx context.Context, it T) bool

Check performs a send and returns true when the send was successful.

func (Send[T]) Ignore

func (sm Send[T]) Ignore(ctx context.Context, it T)

Ignore performs a send and omits the error.

func (Send[T]) Send

func (sm Send[T]) Send(ctx context.Context, it T) (err error)

Send sends the item into the channel captured by Blocking/NonBlocking returning the appropriate error.

type WaitFunc

type WaitFunc func(context.Context)

WaitFunc is a type of function object that will block until an operation returns or the context is canceled.

func WaitBlocking

func WaitBlocking(fn func()) WaitFunc

WaitBlocking is a convenience function to use simple blocking functions into WaitFunc objects. Because these WaitFunc functions do not resepct the WaitFunc context, use with care and caution.

func WaitBlockingObserve

func WaitBlockingObserve[T any](observe func(T), wait func() T) WaitFunc

WaitBlockingObserve is a convenience function that creates a WaitFunc that wraps a simple function that returns a single value, and observes that output with the observer function.

Because these WaitFunc functions do not resepct the WaitFunc context, use with care and caution.

func WaitChannel

func WaitChannel[T any](ch <-chan T) WaitFunc

WaitChannel converts a channel (typically, a `chan struct{}`) to a WaitFunc. The WaitFunc blocks till it's context is canceled or the channel is either closed or returns one item.

func WaitContext

func WaitContext(ctx context.Context) WaitFunc

WaitContext wait's for the context to be canceled before returning. The WaitFunc that's return also respects it's own context. Use this WaitFunc and it's own context to wait for a context to be cacneled with a timeout, for instance.

func WaitForGroup

func WaitForGroup(wg *sync.WaitGroup) WaitFunc

WaitForGroup converts a sync.WaitGroup into a fun.WaitFunc.

This operation will leak a go routine if the WaitGroup never returns and the context is canceled. To avoid a leaked goroutine, use the fun.WaitGroup type.

func WaitMerge

func WaitMerge(ctx context.Context, iter Iterator[WaitFunc]) WaitFunc

WaitMerge starts a goroutine that blocks on each WaitFunc provided and returns a WaitFunc that waits for all of these goroutines to return. The constituent WaitFunc are passed WaitMerge's context, while the returned WaitFunc respects its own context.

Use itertool.Variadic, itertool.Slice, or itertool.Channel to convert common container types/calling patterns to an iterator.

In combination with erc.CheckWait, you can use WaitMerge to create and pubsub.Queue or pubsub.Deque blocking iterators to create worker pools.

func WaitObserve

func WaitObserve[T any](observe Observer[T], ch <-chan T) WaitFunc

WaitObserve passes the output of the channel into the observer function and then returns. If the context is canceled the output of the channel is not observed.

WaitObserve consumes and observes, at most, one item from the channel. Callers must call the WaitFunc.

func WaitObserveAll

func WaitObserveAll[T any](observe Observer[T], ch <-chan T) WaitFunc

WaitObserveAll passes the output of the channel into the observer function, waiting for the input channel to be closed or the WaitFunc's context to be canceled. WaitObserveAll does not begin processing the channel until the WaitFunc is called.

func WaitObserveAllCtx

func WaitObserveAllCtx[T any](observe func(context.Context, T), ch <-chan T) WaitFunc

WaitObserveAllCtx passes the output of the channel into the observer function with a context, waiting for the input channel to be closed or the WaitFunc's context to be canceled. WaitObserveAll does not begin processing the channel until the WaitFunc is called.

func (WaitFunc) Add

func (wf WaitFunc) Add(ctx context.Context, wg *WaitGroup)

Add starts a goroutine that waits for the WaitFunc to return, incrementing and decrementing the sync.WaitGroup as appropriate. The execution of the wait fun blocks on Add's context.

func (WaitFunc) Block

func (wf WaitFunc) Block()

Block runs the WaitFunc with a context that will never be canceled.

func (WaitFunc) BlockSignal

func (wf WaitFunc) BlockSignal() <-chan struct{}

BlockSignal runs the WaitFunc in a background goroutine and returns a signal channel that is closed when the operation completes. As in Block() the WaitFunc is passed a background context that is never canceled.

Callers are responsble for handling the (potential) panic in the WaitFunc.

func (WaitFunc) Check

func (wf WaitFunc) Check() WorkerFunc

Check converts a wait function into a WorkerFunc, running the wait function inside of a Check() function, which catches panics and turns them into the worker function's errors. If the context errors, the Check function's error also propogates a merged error that includes the context's cancelation error

func (WaitFunc) Run

func (wf WaitFunc) Run(ctx context.Context)

Run is equivalent to calling the wait function directly, except the context passed to the function is always canceled when the wait function returns.

func (WaitFunc) Safe

func (wf WaitFunc) Safe() WorkerFunc

Safe produces a worker function that catches. This is the same as WaitFunc.Check() except check will also propgate the context error, which this WorkerFunc will not.

func (WaitFunc) Signal

func (wf WaitFunc) Signal(ctx context.Context) <-chan struct{}

Signal runs the WaitFunc in a goroutine and returns a signal channel that is canceled when the function completes. Useful for bridging the gap between interfaces and integration that use channels and functions.

Callers are responsble for handling the (potential) panic in the WaitFunc.

func (WaitFunc) WithTimeout

func (wf WaitFunc) WithTimeout(timeout time.Duration)

WithTimeout runs the WaitFunc with an explicit timeout.

func (WaitFunc) WithTimeoutSignal

func (wf WaitFunc) WithTimeoutSignal(timeout time.Duration) <-chan struct{}

WithTimeoutSignal executes the WaitFunc as in WithTimeout, but returns a singal channel that is closed when the task completes.

Callers are responsble for handling the (potential) panic in the WaitFunc.

func (WaitFunc) Worker

func (wf WaitFunc) Worker() WorkerFunc

Worker converts a wait function into a WorkerFunc. If the context is canceled, the worker function returns the context's error. The worker function also captures the wait functions panic and converts it to an error.

type WaitGroup

type WaitGroup struct {
	// contains filtered or unexported fields
}

WaitGroup works like sync.WaitGroup, except that the Wait method takes a context (and can be passed as a fun.WaitFunc). The implementation is exceptionally simple. The only constraint, like sync.WaitGroup, is that you can never modify the value of the internal counter such that it is negative, event transiently. The implementation does not require background resources aside from Wait, which creates a single goroutine that lives for the entire time that Wait is running, but no other background resources are created. Multiple copies of Wait can be safely called at once, and the WaitGroup is reusable more than once.

This implementation is about 50% slower than sync.WaitGroup after informal testing. It provides a little extra flexiblity and introspection, with similar semantics, that may be worth the additional performance hit.

func (*WaitGroup) Add

func (wg *WaitGroup) Add(num int)

Add modifies the internal counter. Raises an ErrInvariantViolation error if any modification causes the internal coutner to be less than 0.

func (*WaitGroup) Done

func (wg *WaitGroup) Done()

Done marks a single operation as done.

func (*WaitGroup) IsDone

func (wg *WaitGroup) IsDone() bool

IsDone returns true if there is pending work, and false otherwise.

func (*WaitGroup) Num

func (wg *WaitGroup) Num() int

Num returns the number of pending workers.

func (*WaitGroup) Wait

func (wg *WaitGroup) Wait(ctx context.Context)

Wait blocks until either the context is canceled or all items have completed.

Wait is pasable or usable as a fun.WaitFunc.

In many cases, callers should not rely on the Wait operation returning after the context expires: If Done() calls are used in situations that respect a context cancellation, aborting the Wait on a context cancellation, particularly when Wait gets a context that has the same lifecycle as the operations its waiting on, the result is that worker routines will leak. Nevertheless, in some situations, when workers may take a long time to respond to a context cancellation, being able to set a second deadline on Waiting may be useful.

Consider using `fun.WaitFunc(wg.Wait).Block()` if you want blocking semantics with the other features of this WaitGroup implementation.

type WorkerFunc

type WorkerFunc func(context.Context) error

WorkerFunc represents a basic function used in worker pools and other similar situations

func ObserveWorker

func ObserveWorker[T any](iter Iterator[T], fn Observer[T]) WorkerFunc

ObserveWorker has the same semantics as Observe, except that the operation is wrapped in a WaitFunc, and executed when the WaitFunc is called.

func (WorkerFunc) Add

func (wf WorkerFunc) Add(ctx context.Context, wg *WaitGroup, ob Observer[error])

Add runs the worker function in a go routine

func (WorkerFunc) Background

func (wf WorkerFunc) Background(ctx context.Context, ob Observer[error])

Background runs the worker function in a go routine and passes the output to the provided observer function.

func (WorkerFunc) Block

func (wf WorkerFunc) Block() error

Block executes the worker function with a context that will never expire and returns the error. Use with caution

func (WorkerFunc) MustWait

func (wf WorkerFunc) MustWait() WaitFunc

MustWait converts a Worker function into a wait function; however, if the worker produces an error MustWait converts the error into a panic.

func (WorkerFunc) Observe

func (wf WorkerFunc) Observe(ctx context.Context, ob Observer[error])

Observe runs the worker function, and observes the error (or nil response). Panics are converted to errors for both the worker function but not the observer function.

func (WorkerFunc) ObserveWait

func (wf WorkerFunc) ObserveWait(ob Observer[error]) WaitFunc

ObserveWait converts a worker function into a wait function, passing any error to the observer function. Only non-nil errors are observed.

func (WorkerFunc) Run

func (wf WorkerFunc) Run(ctx context.Context) error

Run is equivalent to calling the worker function directly, except the context passed to it is canceled when the worker function returns.

func (WorkerFunc) Safe

func (wf WorkerFunc) Safe(ctx context.Context) (err error)

Safe runs the worker function and converts the worker function to a panic to an error.

func (WorkerFunc) Singal

func (wf WorkerFunc) Singal(ctx context.Context) <-chan error

Signal runs the worker function in a background goroutine and returns the error in an error channel, that returns when the worker function returns. If Singal is called with a canceled context the worker is still executed (with that context.)

A value, possibly nil, is always sent through the channel, though the WorkerFunc runs in a different go routine, a panic handler will convert panics to errors.

func (WorkerFunc) WithTimeout

func (wf WorkerFunc) WithTimeout(timeout time.Duration) error

WithTimeout executes the worker function with the provided timeout using a new context.