Implement ToolCommandlet for Yarn

[hohwille]

Create ToolCommandlet for Yarn
Old commandlet:
https://github.com/devonfw/ide/blob/master/scripts/src/main/resources/scripts/command/yarn

See also #441

[julia-cap]

Yarn is installed via npm. It should be implemented as DelegatingToolCommandlet referring to npm.

[julia-cap]

Since Yarn Modern (2+), there is a different way of installing Yarn: It is recommended to use corepack, see documentation here. Yarn Classic (1.x), however, can be installed by executing yarn set version classic (true, if yarn is not installed?!). After conducting some research, it seems that many projects are still using Yarn Classic, so I suggest IDEasy should support this, too. Interesting read on that is here.

Yarn project explicitly recommends to use corepack for installing yarn. Yet, corepack is in experimental state and various issues can be found on e.g. stackoverflow.

Question 1: Should we follow the recommendation or rather stick to the traditional way of installing yarn and use npm? Or decide on how to install yarn depending on the version of yarn i.e. using npm for yarn 1.x and corepack for yarn v2+?

Question 2: If we are going to use corepack, should yarn rather be installed in the local software path but not the repo, i.e. where npm is installed. But not inside the npm directory?

During installation, I would execute the cmd command for installing yarn as there aren't installers provided for all versions and OS. If no version is given, the latest possible version will be installed.

Additionally, a dependencies.json will have to be created because in order to install Yarn, we need npm or corepack and possibly Node, again dependent on the Yarn version and on the answer to the question 1 above.

[hohwille]

@julia-cap thanks for your research and elaborated summary of the situation.
The renaming of yarn 1.x to yarn classic and the comments about this ("Yarn Classic (v1) and Yarn Modern (also known as Yarn Berry; v2+) are completely different things") tend me to the idea that we should by default install Yarn Modern and only support Yarn Classic as backward compatibility. The way to solve things like that would be using YARN_EDITION.
However, currently yarn does not exist at all in ide-urls since we do not download and install it regular but via other tools like npm. So as long as this stays, we even do not need to distinguish editions and can simply derive from the version what to do (Otherwise it could cause a lot of custom logic esp. in URL updaters if we have if (version < 2.0) { doModernStuff(); } else { doClassicStuff(); } instead of separating the editions).

Question 1

IMHO the default for IDEasy is to provide modern tooling to developers. Still we want to be flexible and also support other use-cases and legacy support. So if nothing else is configured «TOOL»_VERSION defaults to * meaning the latest version ("latest is greatest"). That means out of the box you will then get Yarn Modern. A project that wants to have Yarn Classic would need to explicitly configure YARN_VERSION=1.* or even an explicit version.

The installation then most likely needs to do this version < 2.0 check and implement two different ways of the installation.
Creating two different commandlets instead would not really help here: What if a user then installs both Yarn Classic and Yarn Modern in the same project and runs yarn on the commandline?

Question 2

It seems that again the JavaScript ecosystem is trying to make things complicated for developers and therefore also for us in IDEasy.
See also here.
In such case, before implementing anything it is always recommended to first manually install Yarn (Modern) following the documentation and best-practices given on the web. Then we check if that works and is still compliant with our IDEasy principles like the sandbox.
If we then understood what to do, we can start automating it by implementing the logic in our Yarn commandlet.

As it turns out, we often underestimate stories.
Thanks again for finding all this out and stepping in early before you create implementations that we might otherwise need to throw away or completely refactor...
Seems that the next steps for this story require some collaboration and interaction.
Feel free to keep asking questions or creating an appointment for a workshop of the topic.
I guess the part for version < 2.0 should be quite clear and could already be implemented while the else part could remain a TODO unless further research and clarification is done.
I am also not a JavaScript, Node.js, or corepack expert - from my experience with npm and yarn and the "concept" of node_modules I have the problem that I grew up with Java and Maven that has a IMHO so much better design and elaborated concept that it always hurts to work in this Node.js world as a developer. Anyhow supporting this world in IDEasy is a necessity and should not be neglected. Maybe we could use our internal communities to find experts from this ecosystem, to give us some additional guidance and hits...

[julia-cap]

Hi @hohwille,
Thank you for sharing your detailed thoughts on this. In Question 1 I meant exactly what you suggest: Having two different implementations for the installation, depending on the given Yarn version. Yet, I don't understand why the implementation for version < 2.0 should be clearer than for version >= 2.0. Is that because we have some knowledge of yarn installation via npm, but not of yarn installation via corepack?

So, summing it up, we have those two ways of installing yarn depending on the version, and before implementing anything we should test manually to learn about the installation behavior?

[hohwille]

For the record:

$ ide create java-quarkus https://github.com/devonfw-training/java-quarkus-settings.git
...
Start: Install or update software
Step 'Install or update software' ended with failure.
Step 'ide (create,java-quarkus)' failed: java.lang.IllegalArgumentException: The commandlet yarn could not be found!
 Step 'Install or update software' failed: unexpected error
2 step(s) failed out of 4 steps.
An unexpected error occurred!
We are sorry for the inconvenience.
Please check the error below, resolve it and try again.
If the error is not on your end (network connectivity, lack of permissions, etc.) please file a bug:
https://github.com/devonfw/IDEasy/issues/new?assignees=&labels=bug&projects=&template=bug.md&title=IllegalArgumentException%3A+The+commandlet+yarn+could+not+be+found%21
java.lang.IllegalArgumentException: The commandlet yarn could not be found!
        at com.devonfw.tools.ide.commandlet.CommandletManager.getRequiredCommandlet(CommandletManager.java:52)
        at com.devonfw.tools.ide.commandlet.CommandletManager.getRequiredToolCommandlet(CommandletManager.java:77)
        at com.devonfw.tools.ide.commandlet.AbstractUpdateCommandlet.updateSoftware(AbstractUpdateCommandlet.java:179)
        at com.devonfw.tools.ide.commandlet.AbstractUpdateCommandlet.run(AbstractUpdateCommandlet.java:63)
        at com.devonfw.tools.ide.commandlet.CreateCommandlet.run(CreateCommandlet.java:64)
        at com.devonfw.tools.ide.context.AbstractIdeContext.applyAndRun(AbstractIdeContext.java:958)
        at com.devonfw.tools.ide.context.AbstractIdeContext.run(AbstractIdeContext.java:876)
        at com.devonfw.tools.ide.cli.Ideasy.runOrThrow(Ideasy.java:95)
        at com.devonfw.tools.ide.cli.Ideasy.run(Ideasy.java:59)
        at com.devonfw.tools.ide.cli.Ideasy.main(Ideasy.java:133)
        at java.base@21.0.2/java.lang.invoke.LambdaForm$DMH/sa346b79c.invokeStaticInit(LambdaForm$DMH)
Error: IDEasy failed with exit code 255