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.)

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.

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 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 Must[T any](arg T, err error) T
• func Safe[T any](fn func() T) (out T, err error)
• func SafeCtx[T any](ctx context.Context, fn func(context.Context) T) (out T, err error)
• func Unwrap[T any](in T) T
• func Wait(ctx context.Context, wg *sync.WaitGroup)
• func WaitAdd(ctx context.Context, wg *sync.WaitGroup, fn WaitFunc)
• type Iterator
• type WaitFunc
  • func WaitChannel[T any](ch <-chan T) WaitFunc
  • func WaitContext(ctx context.Context) WaitFunc
  • func WaitGroup(wg *sync.WaitGroup) WaitFunc
  • func WaitMerge(ctx context.Context, iter Iterator[WaitFunc]) WaitFunc
  • func WaitObserve[T any](observe func(T), ch <-chan T) WaitFunc
  • func WaitObserveAll[T any](observe func(T), ch <-chan T) WaitFunc
  • func (wf WaitFunc) Block()

Variables

var ErrInvariantViolation = errors.New("invariant violation")

ErrInvariantViolation is the root error of the error object that is the content of all panics produced by the Invariant helper.

Functions

func Check

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

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

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 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 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 SafeCtx

func SafeCtx[T any](ctx context.Context, fn func(context.Context) T) (out T, err error)

SafeCtx provides a variant of the Safe function that takes a context.

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 Wait

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

Wait returns when the all waiting items are done, *or* the context is canceled. This operation will leak a go routine if the WaitGroup never returns and the context is canceled.

fun.Wait(wg) is equivalent to fun.WaitGroup(wg)(ctx)

func WaitAdd

func WaitAdd(ctx context.Context, wg *sync.WaitGroup, fn WaitFunc)

WaitAdd starts a goroutine that waits for the WaitFunc to return, incrementing and decrementing the sync.WaitGroup as appropriate. This WaitFunc blocks on WaitAdd's context.

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, Filter 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.

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 WaitChannel

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

WaitChannel converts a channel (typically, a `chan struct{}`) to a

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 WaitGroup

func WaitGroup(wg *sync.WaitGroup) WaitFunc

WaitGroup converts a WaitGroup into a fun.WaitFunc.

This operation will leak a go routine if the WaitGroup never returns and the context is canceled.

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.

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

func WaitObserve

func WaitObserve[T any](observe func(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 func(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 (WaitFunc) Block

func (wf WaitFunc) Block()

Block executes the wait function with a context that will never expire. Use with extreme caution.