This library contains additional computation expressions for the task CE utilizing the Resumable Code introduced in F# 6.0.
-
ValueTask<'T>
- This utilizes .NET's ValueTask (which is essentially a Discriminated Union of'Value | Task<'Value>
) for possibly better performance in synchronous scenarios. Similar to F#'s Task ExpressionvalueTask
valueTaskUnit
poolingValueTask
-
ColdTask<'T>
- Alias forunit -> Task<'T>
. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold.coldTask
-
CancellableTask<'T>
- Alias forCancellationToken -> Task<'T>
. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold. Additionally, allows for flowing a CancellationToken through the computation, similar to F#'s Async cancellation support.cancellableTask
cancellableBackgroundTask
-
CancellableValueTask<'T>
- Alias forCancellationToken -> ValueTask<'T>
. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold. Additionally, allows for flowing a CancellationToken through the computation, similar to F#'s Async cancellation support.cancellableValueTask
cancellablePoolingValueTask
-
ParallelAsync<'T>
- Utilizes the applicative syntax to allow parallel execution of Async<'T> expressions. See this discussion as to why this is a separate computation expression.parallelAsync
-
AsyncEx<'T>
- Variation of F# async semantics described further below with examples.asyncEx
- This can also be accessed under
IcedTasks.Polyfill.Async
which will shadow the F# Async CE.async
-
Task<'T>
- Polyfill for fixes to F# Task CE. Can be accessed underIcedTasks.Polyfill.Task
which will shadow the F# Task CE.task
backgroundTask
-
Task
- a CE for aTask
that has no return value.taskUnit
backgroundTaskUnit
Computation Expression1 | Library2 | TFM3 | Hot/Cold4 | Multiple Awaits 5 | Multi-start6 | Tailcalls7 | CancellationToken propagation8 | Cancellation checks9 | Parallel when using and!10 | use IAsyncDisposable 11 |
---|---|---|---|---|---|---|---|---|---|---|
F# Async | FSharp.Core | netstandard2.0 | Cold | Multiple | multiple | tailcalls | implicit | implicit | No | No |
F# AsyncEx | IcedTasks | netstandard2.0 | Cold | Multiple | multiple | tailcalls | implicit | implicit | No | Yes |
F# ParallelAsync | IcedTasks | netstandard2.0 | Cold | Multiple | multiple | tailcalls | implicit | implicit | Yes | No |
F# Task/C# Task | FSharp.Core | netstandard2.0 | Hot | Multiple | once-start | no tailcalls | explicit | explicit | No | Yes |
F# ValueTask | IcedTasks | netstandard2.0 | Hot | Once | once-start | no tailcalls | explicit | explicit | Yes | Yes |
F# ColdTask | IcedTasks | netstandard2.0 | Cold | Multiple | multiple | no tailcalls | explicit | explicit | Yes | Yes |
F# CancellableTask | IcedTasks | netstandard2.0 | Cold | Multiple | multiple | no tailcalls | implicit | implicit | Yes | Yes |
F# CancellableValueTask | IcedTasks | netstandard2.0 | Cold | Once | multiple | no tailcalls | implicit | implicit | Yes | Yes |
- 1 - Computation Expression
- 2 - Which Nuget package do they come from
- 3 - Which Target Framework Moniker these are available in
- 4 - Hot refers to the asynchronous code block already been started and will eventually produce a value. Cold refers to the asynchronous code block that is not started and must be started explicitly by caller code. See F# Async Tutorial and Asynchronous C# and F# (II.): How do they differ? for more info.
- 5 - ValueTask Awaiting patterns
- 6 - Multi-start refers to being able to start the asynchronous code block again. See FAQ on Task Start for more info.
- 7 - Allows use of
let rec
with the computation expression. See Tail call Recursion for more info. - 8 -
CancellationToken
is propagated to all types the support implicitCancellatationToken
passing. CallingcancellableTask { ... }
nested insideasync { ... }
(or any of those combinations) will use theCancellationToken
from when the code was started. - 9 - Cancellation will be checked before binds and runs.
- 10 - Allows parallel execution of the asynchronous code using the Applicative Syntax in computation expressions.
- 11 - Allows
use
ofIAsyncDisposable
with the computation expression. See IAsyncDisposable for more info.
AsyncEx is similar to Async except in the following ways:
-
Allows
use
for IAsyncDisposableopen IcedTasks let fakeDisposable () = { new IAsyncDisposable with member __.DisposeAsync() = ValueTask.CompletedTask } let myAsyncEx = asyncEx { use _ = fakeDisposable () return 42 }
-
Allows
let!/do!
against Tasks/ValueTasks/any Awaitableopen IcedTasks let myAsyncEx = asyncEx { let! _ = task { return 42 } // Task<T> let! _ = valueTask { return 42 } // ValueTask<T> let! _ = Task.Yield() // YieldAwaitable return 42 }
-
When Tasks throw exceptions they will use the behavior described in Async.Await overload (esp. AwaitTask without throwing AggregateException
let data = "lol" let inner = asyncEx { do! task { do! Task.Yield() raise (ArgumentException "foo") return data } :> Task } let outer = asyncEx { try do! inner return () with | :? ArgumentException -> // Should be this exception and not AggregationException return () | ex -> return raise (Exception("Should not throw this type of exception", ex)) }
-
Use IAsyncEnumerable with
for
keyword. This example uses TaskSeq but you can use anyIAsyncEnumerable<T>
.open IcedTasks open FSharp.Control let myAsyncEx = asyncEx { let items = taskSeq { // IAsyncEnumerable<T> yield 42 do! Task.Delay(100) yield 1701 } let mutable sum = 0 for i in items do sum <- sum + i return sum }
For ValueTasks
- F# doesn't currently have a
valueTask
computation expression. Until this PR is merged.
open IcedTasks
let myValueTask = task {
let! theAnswer = valueTask { return 42 }
return theAnswer
}
- You want control over when your tasks are started
- You want to be able to re-run these executable tasks
- You don't want to pollute your methods/functions with extra CancellationToken parameters
- You want the computation to handle checking cancellation before every bind.
Short example:
open IcedTasks
let coldTask_dont_start_immediately = task {
let mutable someValue = null
let fooColdTask = coldTask { someValue <- 42 }
do! Async.Sleep(100)
// ColdTasks will not execute until they are called, similar to how Async works
Expect.equal someValue null ""
// Calling fooColdTask will start to execute it
do! fooColdTask ()
Expect.equal someValue 42 ""
}
The examples show cancellableTask
but cancellableValueTask
can be swapped in.
Accessing the context's CancellationToken:
-
Binding against
CancellationToken -> Task<_>
let writeJunkToFile = let path = Path.GetTempFileName() cancellableTask { let junk = Array.zeroCreate bufferSize use file = File.Create(path) for i = 1 to manyIterations do // You can do! directly against a function with the signature of `CancellationToken -> Task<_>` to access the context's `CancellationToken`. This is slightly more performant. do! fun ct -> file.WriteAsync(junk, 0, junk.Length, ct) }
-
Binding against
CancellableTask.getCancellationToken
let writeJunkToFile = let path = Path.GetTempFileName() cancellableTask { let junk = Array.zeroCreate bufferSize use file = File.Create(path) // You can bind against `CancellableTask.getCancellationToken` to get the current context's `CancellationToken`. let! ct = CancellableTask.getCancellationToken () for i = 1 to manyIterations do do! file.WriteAsync(junk, 0, junk.Length, ct) }
Short example:
let executeWriting = task {
// CancellableTask is an alias for `CancellationToken -> Task<_>` so we'll need to pass in a `CancellationToken`.
// For this example we'll use a `CancellationTokenSource` but if you were using something like ASP.NET, passing in `httpContext.RequestAborted` would be appropriate.
use cts = new CancellationTokenSource()
// call writeJunkToFile from our previous example
do! writeJunkToFile cts.Token
}
- When you want to execute multiple asyncs in parallel and wait for all of them to complete.
Short example:
open IcedTasks
let exampleHttpCall url = async {
// Pretend we're executing an HttpClient call
return 42
}
let getDataFromAFewSites = parallelAsync {
let! result1 = exampleHttpCall "howManyPlantsDoIOwn"
and! result2 = exampleHttpCall "whatsTheTemperature"
and! result3 = exampleHttpCall "whereIsMyPhone"
// Do something meaningful with results
return ()
}
GitHub Actions |
---|
Package | Stable | Prerelease |
---|---|---|
IcedTasks |
Make sure the following requirements are installed on your system:
- dotnet SDK 6.0 & 8.0
or
CONFIGURATION
will set the configuration of the dotnet commands. If not set, it will default to Release.CONFIGURATION=Debug ./build.sh
will result in-c
additions to commands such as indotnet build -c Debug
GITHUB_TOKEN
will be used to upload release notes and Nuget packages to GitHub.- Be sure to set this before releasing
> build.cmd <optional buildtarget> // on windows
$ ./build.sh <optional buildtarget>// on unix
The bin of your library should look similar to:
$ tree src/MyCoolNewLib/bin/
src/MyCoolNewLib/bin/
└── Debug
└── net50
├── MyCoolNewLib.deps.json
├── MyCoolNewLib.dll
├── MyCoolNewLib.pdb
└── MyCoolNewLib.xml
Clean
- Cleans artifact and temp directories.DotnetRestore
- Runs dotnet restore on the solution file.DotnetBuild
- Runs dotnet build on the solution file.DotnetTest
- Runs dotnet test on the solution file.GenerateCoverageReport
- Code coverage is run duringDotnetTest
and this generates a report via ReportGenerator.WatchTests
- Runs dotnet watch with the test projects. Useful for rapid feedback loops.GenerateAssemblyInfo
- Generates AssemblyInfo for libraries.DotnetPack
- Runs dotnet pack. This includes running Source Link.SourceLinkTest
- Runs a Source Link test tool to verify Source Links were properly generated.PublishToNuGet
- Publishes the NuGet packages generated inDotnetPack
to NuGet via paket push.GitRelease
- Creates a commit message with the Release Notes and a git tag via the version in theRelease Notes
.GitHubRelease
- Publishes a GitHub Release with the Release Notes and any NuGet packages.FormatCode
- Runs Fantomas on the solution file.BuildDocs
- Generates Documentation fromdocsSrc
and the XML Documentation Comments from your libraries insrc
.WatchDocs
- Generates documentation and starts a webserver locally. It will rebuild and hot reload if it detects any changes made todocsSrc
files, libraries insrc
, or thedocsTool
itself.ReleaseDocs
- Will stage, commit, and push docs generated in theBuildDocs
target.Release
- Task that runs all release type tasks such asPublishToNuGet
,GitRelease
,ReleaseDocs
, andGitHubRelease
. Make sure to read Releasing to setup your environment correctly for releases.
git add .
git commit -m "Scaffold"
git remote add origin https://github.com/user/MyCoolNewLib.git
git push -u origin master
-
paket config add-token "https://www.nuget.org" 4003d786-cc37-4004-bfdf-c4f3e8ef9b3a
- or set the environment variable
NUGET_TOKEN
to your key
- or set the environment variable
-
- You can then set the environment variable
GITHUB_TOKEN
to upload release notes and artifacts to github - Otherwise it will fallback to username/password
- You can then set the environment variable
-
Then update the
CHANGELOG.md
with an "Unreleased" section containing release notes for this version, in KeepAChangelog format.
NOTE: Its highly recommend to add a link to the Pull Request next to the release note that it affects. The reason for this is when the RELEASE
target is run, it will add these new notes into the body of git commit. GitHub will notice the links and will update the Pull Request with what commit referenced it saying "added a commit that referenced this pull request". Since the build script automates the commit message, it will say "Bump Version to x.y.z". The benefit of this is when users goto a Pull Request, it will be clear when and which version those code changes released. Also when reading the CHANGELOG
, if someone is curious about how or why those changes were made, they can easily discover the work and discussions.
Here's an example of adding an "Unreleased" section to a CHANGELOG.md
with a 0.1.0
section already released.
## [Unreleased]
### Added
- Does cool stuff!
### Fixed
- Fixes that silly oversight
## [0.1.0] - 2017-03-17
First release
### Added
- This release already has lots of features
[Unreleased]: https://github.com/user/MyCoolNewLib.git/compare/v0.1.0...HEAD
[0.1.0]: https://github.com/user/MyCoolNewLib.git/releases/tag/v0.1.0
- You can then use the
Release
target, specifying the version number either in theRELEASE_VERSION
environment variable, or else as a parameter after the target name. This will:- update
CHANGELOG.md
, moving changes from theUnreleased
section into a new0.2.0
section- if there were any prerelease versions of 0.2.0 in the changelog, it will also collect their changes into the final 0.2.0 entry
- make a commit bumping the version:
Bump version to 0.2.0
and adds the new changelog section to the commit's body - publish the package to NuGet
- push a git tag
- create a GitHub release for that git tag
- update
macOS/Linux Parameter:
./build.sh Release 0.2.0
macOS/Linux Environment Variable:
RELEASE_VERSION=0.2.0 ./build.sh Release