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Key Takeaways

supply turbines are a great way to cut back the amount of repetitive code that has to be written.

Plan your source generator by means of first determining how drinking tasks will use it.?

do not use a supply generator if the input is whatever unreliable reminiscent of a database.

discovering the Roslyn syntax tree isnt required, but it will offer you more alternatives.?

listed here well be writing a source generator for C#. Along the manner well explain one of the vital key applied sciences youre going to need to study in order to build your own and some of the pitfalls you could encounter on the way.

When starting a brand new source generator, the primary question is, of course, "What are you trying to accomplish?".

but following closely behind is, "Does this make experience as a source generator?". Here is a crucial question, for the reason that supply generators run anytime the code is recompiled.

So, if your code generator wants records from an exterior source, corresponding to a database, a supply generator is doubtless no longer appropriate.

For this stroll-through, well be searching at the supply code for Tortuga look at various Monkey. It is accessible on Github under beneath the MIT License.

task goal

When writing unit exams, many of the checks vital for insurance are low value; the odds of them really detecting an error are perhaps one in 100 or much less.

heres an instance of testing property getters and setters to insure they operate as meant:

[TestMethod] public void @FirstName_SelfAssign() var objectUnderTest = CreateObject(); var originalValue = objectUnderTest.@FirstName; objectUnderTest.FirstName = originalValue; Assert.AreEqual(originalValue, objectUnderTest.@FirstName, "Assigning a property to itself should not trade its value."); [TestMethod] public void @FirstName_DoubleRead() var objectUnderTest = CreateObject(); var readOnce = objectUnderTest.@FirstName; var readTwice = objectUnderTest.@FirstName; Assert.AreEqual(readOnce, readTwice, "analyzing a property twice may still return the same cost both times.");

nobody desires to put in writing these checks as a result of they re tedious and virtually in no way become aware of a bug. But nearly never isnt the identical as by no means and they may still be validated.What if we will use a code generator to create these low price exams? If we cut back them to simply an attribute, we may get out verify insurance whereas releasing up the developer to focus on the extra complex exams.

[TestClass] [MakeTests(typeof(SimpleClass), TestTypes.All)] public partial type Test_SimpleClass

in this stroll through, well discover the way to create this sort of look at various generator.

mission structure

on the naked minimum you need two tasks, one for the supply generator itself and one to verify it against. For your supply generator, you deserve to make right here additions to the challenge file.

First, you deserve to set the target framework to .Net normal 2.0. Here s required via the C# compiler, so it isn t optional. In addition, your whole dependencies must likewise be for .Net normal 2.0 or previous.

<TargetFramework>netstandard2.0</TargetFramework>

Then add the CodeAnalysis libraries from NuGet.

then you are going to want to indicate here is an "analyzer". If you skip this step, your supply generator wont work when deployed as a NuGet kit.

<ItemGroup> <None include="$(OutputPath)$(AssemblyName).Dll" Pack="genuine" PackagePath="analyzers/dotnet/cs" visible="false" /> </ItemGroup> purchaser assignment Settings

next you should come to a decision if the project ingesting the source generator may be the usage of it at runtime or most effective assemble time. If it is most effective used at compile time and doesnt have any courses the consuming mission wants, then you can add right here.

<PropertyGroup> <IncludeBuildOutput>false</IncludeBuildOutput> </PropertyGroup>

In our case, Tortuga.TestMonkey.Dll comprises a few public classes the drinking challenge needs, above all an attribute and matching enum, so we aren t the usage of the above environment.

if you appear at the Tortuga.TestMonkey.Csproj file on GitHub, youll also see a piece titled "NuGet Packaging Boilerplate". This has nothing to do with source turbines, it just makes publishing the NuGet equipment a little bit easier.

On the customer side, youll need to reference the supply generator. You could do that as a task reference or a kit reference.

in the above illustration, we reveal both alternate options. This was finished so we may look at various the NuGet equipment in unlock mode while still having the comfort of using a project reference whereas writing the source generator.

in an effort to see the effects of your code generator, you re going to wish to switch on EmitCompilerGeneratedFiles.

<PropertyGroup> <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles> <CompilerGeneratedFilesOutputPath>Generated</CompilerGeneratedFilesOutputPath> </PropertyGroup> <ItemGroup>  <collect eradicate="$(CompilerGeneratedFilesOutputPath)/*/**/*.Cs" /> </ItemGroup>

if you do not hope to your generated code to be checked in, add this line to your .Gitignore file.

**/Generated/Tortuga.TestMonkey/*

For the intention of this walkthrough, youll should create a unit look at various mission a good way to act as the ingesting venture. Youll also want a undertaking being confirmed. In your comfort, these are offered within the supply code examples on GitHub.

The source Generator

The source generator is defined the use of the ISourceGenerator attribute and the ISourceGenerator interface. Both can also be present in the Microsoft.CodeAnalysis namespace.

The Initialize components is used to register for two hobbies, syntax notification and publish-initialization. These aren t EventHandler style movements, so that you may also handiest have certainly one of each and every. For this walkthrough, were handiest going to use RegisterForSyntaxNotifications. Well speak in regards to the use case for RegisterForPostInitialization later in the article.

The syntax notification event wants an ISyntaxContextReceiver. This should be referred to as after the compiler has built the syntax tree from the supply code. In case your supply generator doesnt should analyze the source code, you could skip this step.

The Execute formula is used to definitely generate the supply code. In case you used a syntax receiver, this can run afterwards. Well return to this later in the article, however for now we handiest want this line:

// retrieve the populated receiver if (!(context.SyntaxContextReceiver is SyntaxReceiver receiver)) return;

The receiver variable is a similar object we setup within the Initialize formulation.

The Syntax Receiver

The syntax receiver must put in force the ISyntaxContextReceiver interface. This has a single method referred to as OnVisitSyntaxNode, which is "referred to as for every syntax node within the compilation".

within the examples from Microsoft, the syntax receiver is frequently a private classification inside the source generator class. We selected to no longer go that route as our syntax receiver is a little bit massive and will be less demanding to contend with in its personal file.

In our syntax receiver, there are two residences:

public record<string> Log get; = new(); public listing<WorkItems> WorkItems get; = new();

The work objects are purely an inventory of things we deserve to generate code for. Definitely, it is the to-do record for the source generators Execute components.

The log needs just a little more clarification. We want it as a result of we can not attach a debugger to the compiler itself. Considering the source generator runs internal the compiler, there isnt a good way to look whats truly happening. So, like an old style programmer the usage of Console.WriteLine, we are just going to dump every little thing we will right into a text file.

To set this up, region the following on your syntax receivers OnVisitSyntaxNode system.Try

if (context.Node is ClassDeclarationSyntax classDeclarationSyntax) Log.Add($"discovered a category named testClass.Identify"); capture (Exception ex) Log.Add("Error parsing syntax: " + ex.ToString());

with a purpose to view this log information, we deserve to capture it within the supply generators Execute formulation.

//Write the log entries context.AddSource("Logs", SourceText.From($@"/* ambiance.NewLine + string.Be a part of(environment.NewLine, receiver.Log) + environment.NewLine*/", Encoding.UTF8));

in case you enabled EmitCompilerGeneratedFiles in your ingesting task, be sure to see a file named "GeneratedTortuga.TestMonkeyTortuga.TestMonkey.TestGeneratorLogs.Cs" with contents similar to:

/* found a class named Test_SimpleClass discovered a category named Test_AnotherClass found a class named Test_NoDefaultConstructor discovered a category named Test_SimplePair found a class named AutoGeneratedProgram */ looking for classes

the line "context.Node is ClassDeclarationSyntax classDeclarationSyntax" says were looking for syntax nodes that characterize a class statement. Some other nodes will be skipped.

if you are looking to search for some thing else, which you could use the Roslyn syntax visualizer in visual Studio to determine what kind of syntax node you are looking for. Guidance for installing and the use of this device can be found on Microsoft docs.

For this code generator, we dont truly care a whole lot in regards to the syntax nodes. They lack the guidance we should accomplish our dreams. The subsequent step is to show that syntax node right into a "semantic node". For a category, it might seem like this:

var testClass = (INamedTypeSymbol)context.SemanticModel.GetDeclaredSymbol(context.Node)!;

during this illustration, were going to be checking to see if testClass is a unit examine class with the MakeTests attribute. If we have other courses in our unit look at various venture, those will even be captured.

to peer what we basically have, well leverage our log file.

var attributes = testClass.GetAttributes(); Log.Add($" discovered attributes.Size attributes"); foreach (AttributeData att in attributes) Log.Add($" Attribute: att.AttributeClass!.Name Full identify: att.AttributeClass.FullNamespace()"); foreach (var arg in att.ConstructorArguments) Log.Add($" ....Argument: category= arg.Class Value_Type= arg.Cost?.GetType().FullName price= arg.Cost ");

right here is an excerpt from our up to date log file.

found a class named Test_SimpleClass discovered 2 attributes Attribute: TestClassAttribute Full identify: Microsoft.VisualStudio.TestTools.UnitTesting Attribute: MakeTestsAttribute Full identify: Tortuga.TestMonkey ....Argument: category= system.Class Value_Type= Microsoft.CodeAnalysis.CSharp.Symbols.PublicModel.NonErrorNamedTypeSymbol price= pattern.UnderTest.SimpleClass ........Found a INamedTypeSymbol named sample.UnderTest.SimpleClass ....Argument: category= Tortuga.TestMonkey.TestTypes Value_Type= equipment.Int32 value= -1

Youll word we discovered the attributes on the classification as well as any constructor parameter for these attributes. We may have additionally requested it for att.NamedArguments if we had every other houses on the attribute we needed to study.

one of the most attributes refers to the class being proven. Were going to grab that as neatly as the enumeration indicating which styles of assessments are desired.

var makeTestAttribte = testClass.GetAttributes().FirstOrDefault(att => att.AttributeClass.FullName() == "Tortuga.TestMonkey.MakeTestsAttribute"); if (makeTestAttribte != null) var classUnderTest = (INamedTypeSymbol?)makeTestAttribte.ConstructorArguments[0].Cost; var desiredTests = (TestTypes)(int)(makeTestAttribte.ConstructorArguments[1].Cost ?? 0); if (classUnderTest != null && desiredTests != TestTypes.None && testFramework != TestFramework.Unknown) WorkItems.Add(new(testClass, classUnderTest, desiredTests)); Log.Add($"delivered work item for classUnderTest.FullName()!");

earlier than we circulate on, some extension strategies should be called out. The components FullName() is described in the file SemanticHelper.Cs. In there youll find different such helper features for working with the semantic tree.

Well return to the syntax receiver later for more information, however for now we ve sufficient to delivery working on the code generator.

generating the supply Code

For this subsequent step, we return to the source generators Execute system. To beginning with, we setup a loop based on the work objects collected by the syntax receiver.

foreach (var workItem in receiver.WorkItems) var fileName = workItem.TestClass.FullName() + ".Cs"; var code = new CodeWriter(); //populate code right here context.AddSource(fileName, SourceText.From(code.ToString(), Encoding.UTF8));

The CodeWriter is a simple wrapper around a StringBuilder that handles things like indentation. You could bypass it and use a StringBuilder without delay, however gives a handy place to place repetitive code reminiscent of components declarations.

the primary thing we deserve to add is the look at various frameworks using statements. Here is followed through the namespace and sophistication announcement.

code.AppendLine("//This file become generated through Tortuga check Monkey"); code.AppendLine(); code.AddTestFramework(); code.AppendLine(); the use of (code.BeginScope($"namespace workItem.TestClass.FullNamespace()")) { the usage of (code.BeginScope($"partial class workItem.TestClass.Identify"))

The BeginScope function is an AppendLine that also increases the indentation degree. The FullNamespace is a different extension components from SemanticHelper classification. The category identify is a similar because the type that held the MakeTests attribute.

Enumerating the properties

For every classification of test, well create a separate characteristic. Each and every characteristic begins by using checking to look if that classification of test turned into favored, then it is going to enumerate the residences and emit the appropriate code to our string builder.?

static void PropertySelfAssign(WorkItems workItem, CodeWriter code) if (workItem.TestTypes.HasFlag(TestTypes.PropertySelfAssign)) code.AppendLine(); code.AppendLine("//Property Self-task tests"); foreach (var property in workItem.ClassUnderTest.ReadWriteScalarProperties()) the use of (code.StartTest($"property.Identify_SelfAssign")) code.AppendLine("var objectUnderTest = CreateObject();"); code.AppendLine($"var originalValue = objectUnderTest.@property.Name;"); code.AppendLine($"objectUnderTest.Property.Name = originalValue;"); code.AssertAreEqual("originalValue", $"objectUnderTest.@property.Name", "Assigning a property to itself may still not exchange its cost.");

The extension method ReadWriteScalarProperties is described as such:

public static IEnumerable<IPropertySymbol> ReadWriteScalarProperties(this INamedTypeSymbol image) return image.GetMembers().OfType<IPropertySymbol>().Where(p => (p.GetMethod != null) && (p.SetMethod != null) && !P.Parameters.Any());

be aware we aren t checking to see if the property is public. That suggestions is not attainable, nor fundamental. Any private or interior houses we wouldnt have entry to, are automatically filtered out of the semantic tree by means of the compiler.

Working with Partial methods

within the above code there s a function called CreateObject. Here is essential because the code generator wont all the time be able to create an appropriate object to be proven towards. Perhaps the one created with the default constructor is inappropriate or might be it doesnt also have a default constructor. To solve this issue, the supply generator emits a partial method and matching driver feature.

partial void CreateObject(ref pattern.UnderTest.SimpleClass? ObjectUnderTest); sample.UnderTest.SimpleClass CreateObject() sample.UnderTest.SimpleClass? Influence = null; CreateObject(ref result); if (influence != null) return effect; return new pattern.UnderTest.SimpleClass();

If the caller doesnt override CreateObject(ref T objectUnderTest), then we use the default constructor.

but what if there isnt a default constructor? If so we use the HasDefaultConstructor extension components from SemanticHelper.

public static bool HasDefaultConstructor(this INamedTypeSymbol symbol) return symbol.Constructors.Any(c => c.Parameters.Count() == 0);

As with residences, a non-seen constructor could be filtered out of the semantic tree.

We then emit a slightly distinct helper function on the way to throw an exception, as a consequence causing the check to fail.

pattern.UnderTest.NoDefaultConstructor CreateObject() pattern.UnderTest.NoDefaultConstructor? Influence = null; CreateObject(ref outcome); if (effect != null) return outcome; throw new system.NotImplementedException("Please put in force the system partial void CreateObject(ref sample.UnderTest.NoDefaultConstructor? ObjectUnderTest) .");

This isnt the most effective approach it might have been dealt with. As a substitute of throwing an exception, the developer might have used a required partial components. A required partial method is one which, if not applied, will outcome in a compiler error.

To indicate a partial components is required, you must consist of an access modifier comparable to inner most. For example,

inner most partial sample.UnderTest.NoDefaultConstructor CreateObject();

in contrast to not obligatory partial methods, a required partial formula may additionally return a price. This gets rid of the need for the ref parameter.

Detecting Dependencies

The subsequent concern to be solved is the one of unit test frameworks. Even if we restrict Tortuga test Monkey to only the main three verify frameworks, it nonetheless requires distinctive code to be generated for MSTest, NUnit, and XUnit.

To resolve this, well go returned to the SyntaxReceiver and give it the capability to peer the listing of assemblies referenced with the aid of the look at various undertaking. This listing can also be received from the ContainingModule of a node within the semantic tree.

var testFramework = TestFramework.Unknown; foreach (var meeting in testClass.ContainingModule.ReferencedAssemblies) if (meeting.Identify == "Microsoft.VisualStudio.TestPlatform.TestFramework") testFramework = TestFramework.MSTest; else if (meeting.Name == "nunit.Framework") testFramework = TestFramework.NUnit; else if (meeting.Name == "xunit.Core") testFramework = TestFramework.XUnit;

From there, an easy switch block in the CodeWriter handles the rest.

public void AddTestFramework() change (TestFramework) case TestFramework.MSTest: AppendLine("the usage of Microsoft.VisualStudio.TestTools.UnitTesting;"); destroy; case TestFramework.XUnit: AppendLine("the use of Xunit;"); smash; case TestFramework.NUnit: AppendLine("using NUnit.Framework;"); spoil; the way to decouple the supply generator DLL

In Tortuga.TestMonkey, we decided to enable the unit examine initiatives to at once reference Tortuga.TestMonkey. This is perfect to us because a unit look at various mission is not deployed, so the further dependency isnt an awful lot of a priority.

in your source generator, this may also not be the case. Happily, there s one other option. As a substitute of getting the consuming challenge reference the supply generators courses, you can inject them. Here is accomplished by means of a RegisterForPostInitialization adventure within the Initialize formula. For example,

context.RegisterForPostInitialization(context => context.AddSource("TestTypes", @"the use of gadget; namespace Tortuga.TestMonkey [Flags] internal enum TestTypes /// <abstract> /// do not generate any exams for this type. /// </abstract> None = 0, /// <summary> /// examine a property and assign it to itself, verifying that it hasn t changed. /// </summary> PropertySelfAssign = 1, /// <summary> /// read the identical property twice, anticipating the equal result both instances. /// </summary> PropertyDoubleRead = 2, All = -1 "); );

in case you use this formula, dont neglect to set IncludeBuildOutput to false within the mission settings.

There are some obstacles to this approach you need to be aware about. First, you need to make the helper classes inside. In any other case, you could come to be with naming collisions if numerous libraries use the identical supply generator.

As you could see, the code is simply a big string, which means you re going to no longer get any compiler assist when writing the type. I imply developing the code in a separate scratch challenge to make sure it compiles correctly earlier than pasting it in as a string.

a further problem is greater of an IDE challenge. Visible Studio will no longer at all times see these helper courses. When that happens, the IDE will file compiler error in the editor however that you may correctly build the challenge.

because of these developer adventure issues, I lean in opposition t simply referencing the supply generator DLL without delay when possible.

about the author

Jonathan Allen got his beginning engaged on MIS tasks for a fitness health facility within the late ninety s, bringing them up from entry and Excel to an commercial enterprise solution by means of degrees. After spending 5 years writing computerized trading programs for the economic sector, he grew to become a specialist on plenty of initiatives including the UI for a robotic warehouse, the core tier for cancer analysis utility, and the massive facts wants of an enormous actual property insurance business. In his free time he enjoys learning and writing about martial arts from the 16th century.?

Welcome to use the Traffic xia Software, it is free forever!click me in contact with my telegram_ username :@software202220

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