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Adds ColdTask and CancellableTask computation expressions to F#
$ dotnet add package IcedTasksThis 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 Expression
ColdTask<'T> - Alias for unit -> Task<'T>. Allows for lazy evaluation (also known as Cold) of the tasks, similar to F#'s Async being cold.
CancellableTask<'T> - Alias for CancellationToken -> 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.
CancellableValueTask<'T> - Alias for . Allows for lazy evaluation (also known as Cold) of the tasks, similar to . Additionally, allows for flowing a through the computation, similar to .
CancellationToken -> ValueTask<'T>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.
AsyncEx<'T> - Slight variation of F# async semantics described further below with examples.
| Computation Expression<sup>1</sup> | Library<sup>2</sup> | TFM<sup>3</sup> | Hot/Cold<sup>4</sup> | Multiple Awaits <sup>5</sup> | Multi-start<sup>6</sup> | Tailcalls<sup>7</sup> | CancellationToken propagation<sup>8</sup> | Cancellation checks<sup>9</sup> | Parallel when using and!<sup>10</sup> | use IAsyncDisposable <sup>11</sup> |
|---|---|---|---|---|---|---|---|---|---|---|
| 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 | netstandard2.1 | 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 | netstandard2.1 | Cold | Once | multiple | no tailcalls | implicit | implicit | Yes | Yes |
let rec with the computation expression. See Tail call Recursion for more info.CancellationToken is propagated to all types the support implicit CancellatationToken passing. Calling cancellableTask { ... } nested inside async { ... } (or any of those combinations) will use the CancellationToken from when the code was started.use of IAsyncDisposable with the computation expression. See IAsyncDisposable for more info.AsyncEx is similar to Async except in the following ways:
Allows use for IAsyncDisposable
open IcedTasks
let fakeDisposable = { new IAsyncDisposable with member __.DisposeAsync() = ValueTask.CompletedTask }
let myAsyncEx = asyncEx {
use! _ = fakeDisposable
return 42
}
Allows let!/do! against Tasks/ValueTasks/any Awaitable
open 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))
}
valueTask computation expression. Until this PR is merged.open IcedTasks
let myValueTask = task {
let! theAnswer = valueTask { return 42 }
return theAnswer
}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
}
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 ()
}
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| Package | Stable | Prerelease |
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| IcedTasks |
Make sure the following requirements are installed on your system:
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 in dotnet build -c DebugGITHUB_TOKEN will be used to upload release notes and Nuget packages to GitHub.
DISABLE_COVERAGE Will disable running code coverage metrics. AltCover can have severe performance degradation so it's worth disabling when looking to do a quicker feedback loop.
DISABLE_COVERAGE=1 ./build.sh> build.cmd <optional buildtarget> // on windows
$ ./build.sh <optional buildtarget>// on unixThe 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 during DotnetTest 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 in DotnetPack to NuGet via paket push.GitRelease - Creates a commit message with the Release Notes and a git tag via the version in the Release Notes.GitHubRelease - Publishes a GitHub Release with the Release Notes and any NuGet packages.FormatCode - Runs Fantomas on the solution file.BuildDocs - Generates Documentation from docsSrc and the XML Documentation Comments from your libraries in src.WatchDocs - Generates documentation and starts a webserver locally. It will rebuild and hot reload if it detects any changes made to docsSrc files, libraries in src, or the docsTool itself.ReleaseDocs - Will stage, commit, and push docs generated in the BuildDocs target.Release - Task that runs all release type tasks such as PublishToNuGet, GitRelease, ReleaseDocs, and GitHubRelease. 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 masterpaket config add-token "https://www.nuget.org" 4003d786-cc37-4004-bfdf-c4f3e8ef9b3a
NUGET_TOKEN to your keyGITHUB_TOKEN to upload release notes and artifacts to githubThen 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/v0.1.0Release target, specifying the version number either in the RELEASE_VERSION environment
variable, or else as a parameter after the target name. This will:
CHANGELOG.md, moving changes from the Unreleased section into a new 0.2.0 section
Bump version to 0.2.0 and adds the new changelog section to the commit's bodymacOS/Linux Parameter:
./build.sh Release 0.2.0macOS/Linux Environment Variable:
RELEASE_VERSION=0.2.0 ./build.sh Release