Lunatech course - "Moving forward from Scala 2 to Scala 3"

License: Apache License 2.0

Scala 56.01% Batchfile 0.34% SCSS 6.67% HTML 13.40% JavaScript 23.19% CSS 0.38%

dotty exercises course-slides language training training-materials scala3 course-materials course migration

lunatech-scala2-to-scala3-course's Introduction

Moving Forward from Scala 2 to Scala 3

Description

The target audience for this course is the Scala Application Developer Community. In other words, the focus is on people who use the language to develop 'end-user' applications and not necessarily those developers who design and write libraries, toolkits or frameworks (although they may benefit from what is in this course if they haven't already worked with Scala 3).

The goal of the course is to explore the new features in the Scala language brought by the Scala 3 project.

Approach

We start from an existing Scala 2 application: an [Akka] actor based Sudoku solver. We start from the application as-is, but with an sbt build definition that uses the Scala 3 compiler.

Through a series of exercises, we look at specific Scala 3 features and apply these to the Scala 2 code, thereby transforming it step-by-step into a version that exploits a whole series of nice features offered by the new language.

Note that this course gets updated on regular basis, so keep watching this space!

Course installation

Some prerequisites need to be met in order to install the course. The following components need to be installed:

Coursier
A Java JDK (JDK 11 or 17). Note that Coursier allows you to install a JDK
The cmtc Course Management Tools Client CLI
An IDE

The following sections detail how to install these components.

Install Coursier

The course can be installed using Coursier.

Coursier will, as part of its base installation, install a number of useful applications among which:

sbt - the Scala Build Tool
scala-cli - the Scala interactive toolkit
scala - the Scala REPL
scalac - the Scala compiler
java - JDK 8 by default (we will need to install a more recent version of the JDK)

Coursier, once installed, will make it extremely easy to switch between different versions of the installed tools (such as the Scala compiler and REPL).

If you haven't installed Coursier, install it first by following the Install Scala on your computer instructions.

Install a JDK

If you haven't installed a JDK yet (version 11 or 17), you can do this in the following manner. In a terminal on your system, issue the following command to install JDK 11:

$ cs java --jvm temurin:1.11 --setup
Checking if ~/.profile, ~/.zprofile, ~/.bash_profile need(s) updating.
Some shell configuration files were updated. It is recommended to close this terminal once the setup command is done, and open a new one for the changes to be taken into account

Close the current terminal and start a new one. Verify that the JDK is installed correctly:

$ java -version
openjdk version "11.0.20" 2023-07-18
OpenJDK Runtime Environment Temurin-11.0.20+8 (build 11.0.20+8)
OpenJDK 64-Bit Server VM Temurin-11.0.20+8 (build 11.0.20+8, mixed mode)

Install `cmtc`

During the course, you will use the cmtc command, the Course Management Tools Client CLI.

Install it using Coursier from the command line (all Linux, Mac, or Windows platforms) as follows:

$ cs install --contrib cmtc
Wrote cmtc

Verify that the installation was successful by running the cmtc command. You should see the following output:

$ cmtc
Usage: cmtc <COMMAND>

Commands:
  goto-exercise        Move to a given exercise. Pull in tests and readme files for that exercise
  goto-first-exercise  Move to the first exercise. Pull in tests and readme files for that exercise
  install              Install a course - from either a local directory, a zip file on the local file system or a Github project
  list-exercises       List all exercises and their IDs in the repo. Mark the active exercise with a star
  list-saved-states    List all saved exercise states, if any.
  next-exercise        Move to the next exercise. Pull in tests and readme files for that exercise
  previous-exercise    Move to the previous exercise. Pull in tests and readme files for that exercise
  pull-solution        Pull in all code for the active exercise. All local changes are discarded
  pull-template        Selectively pull in a given file or folder for the active exercise
  restore-state        Restore a previously saved exercise state
  save-state           Save the state of the active exercise
  set-current-course   Sets the current course to point to a directory
  version              Print version info

Install the (Scala Center) "Scala 3 migration course"

Installing this course can be done via the cmtc install command as follows:

$ cmtc install -s scalacenter/scala3-migration-course
Downloading studentified course from 'https://github.com/scalacenter/scala3-migration-course/releases/download/v0.1.0/scala3-migration-course-student.zip' to courses directory

Project scala3-migration-course (v0.1.0) successfully installed to:
  /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course

Current course set to '/Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course'

Exercises in repository:
  1.  *   exercise_000_initial_state
  2.      exercise_001_install_sbt_scala3_migrate
  3.      exercise_002_migrate_dependencies
  4.      exercise_003_migrate_scalac_options
  5.      exercise_004_migrate_syntax
  6.      exercise_005_migrate_types
  7.      exercise_006_update_scala_version

Verifying the course installation

Verify that the course was installed correctly by launching sbt test in the root folder of the course exercises. You should see the following output:

$ sbt test
[info] welcome to sbt 1.9.3 (Eclipse Adoptium Java 11.0.20)
[info] loading settings for project global-plugins from idea.sbt ...
[info] loading global plugins from /Users/ericloots/.sbt/1.0/plugins
[info] loading settings for project scala3-migration-course-build from plugins.sbt ...
[info] loading project definition from /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course/project
[info] loading settings for project main from build.sbt ...
[info] set current project to main (in build file:/Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course/)
[info] compiling 8 Scala sources to /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course/target/scala-2.13/classes ...
[warn] 1 deprecation
[warn] 1 deprecation (since 2.13.11)
[warn] 2 deprecations in total; re-run with -deprecation for details
[warn] three warnings found
[info] compiling 8 Scala sources to /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/scala3-migration-course/target/scala-2.13/test-classes ...
[warn] 1 deprecation
[warn] 1 deprecation (since 2.13.3)
[warn] 2 deprecations in total; re-run with -deprecation for details
[warn] three warnings found
[info] example.SyntaxRewritesTests:
[info]   + parentheses around lambda parameter 0.017s
[info]   + auto-application 0.0s
[info] example.FunctorTests:
[info]   + either left functor 0.002s
[info] example.DiffUtilTests:
[info]   + diff 0.01s
[info] example.CatsTests:
[info]   + combine all strings 0.203s
[info] example.TypeIncompatTests:
[info]   + type incompat 0.0s
[info] example.BetterMonadicForTests:
[info]   + count twice 0.001s
[info] example.ScalametaTests:
[info]   + parse Scala expression 0.076s
|D| example.BuildInfo.scalacOptions = List(-encoding, UTF-8, -target:jvm-1.8, -Xsource:3, -Wunused:imports,privates,locals, -explaintypes)
[info] example.BuildInfoTests:
[info]   + scalacOptions 0.003s
[info] Passed: Total 9, Failed 0, Errors 0, Passed 9
[success] Total time: 4 s, completed 5 Sep 2023, 16:15:22

Install the (Lunatech) "Moving from Scala 2 to Scala 3" course

Installing this course can be done via the cmtc install command as follows:

$ cmtc install -f -s lunatech-labs/lunatech-scala2-to-scala3-course
Downloading studentified course from 'https://github.com/lunatech-labs/lunatech-scala2-to-scala3-course/releases/download/3.0.2/lunatech-scala2-to-scala3-course-student.zip' to courses directory

Project lunatech-scala2-to-scala3-course (3.0.2) successfully installed to:
  /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course

Current course set to '/Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course'

Exercises in repository:
  1.  *   exercise_000_sudoku_solver_initial_state
  2.      exercise_001_dotty_deprecated_syntax_rewriting
  3.      exercise_002_dotty_new_syntax_and_indentation_based_syntax
  4.      exercise_003_top_level_definitions
  5.      exercise_004_parameter_untupling
  6.      exercise_005_extension_methods
  7.      exercise_006_using_and_summon
  8.      exercise_007_givens
  9.      exercise_008_enum_and_export
 10.      exercise_009_union_types
 11.      exercise_010_opaque_type_aliases
 12.      exercise_011_multiversal_equality
 13.      exercise_020_opaque_type_aliases_alt
 14.      exercise_021_multiversal_equality

As can be seen in the above output, cmtc installed the course in the /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course folder. Note that this location is OS specific, so, take a note of the location.

Verifying the course installation

Verify that the course was installed correctly by launching sbt test in the root folder of the course exercises. You should see the following output:

$ sbt test
[info] welcome to sbt 1.9.3 (Eclipse Adoptium Java 11.0.20)
[info] loading settings for project global-plugins from idea.sbt ...
[info] loading global plugins from /Users/ericloots/.sbt/1.0/plugins
[info] loading settings for project lunatech-scala2-to-scala3-course-build from plugins.sbt ...
[info] loading project definition from /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course/project
[info] compiling 1 Scala source to /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course/project/target/scala-2.12/sbt-1.0/classes ...
[info] loading settings for project moving-from-scala-2-to-scala-3 from build.sbt ...
[info] set current project to moving-from-scala-2-to-scala-3 (in build file:/Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course/)
[info] compiling 11 Scala sources to /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course/target/scala-2.13/classes ...
[warn] /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course/src/main/scala/org/lunatechlabs/dotty/sudoku/SudokuProblemSender.scala:81:44: Auto-application to `()` is deprecated. Supply the empty argument list `()` explicitly to invoke method next,
[warn] or remove the empty argument list from its definition (Java-defined methods are exempt).
[warn] In Scala 3, an unapplied method like this will be eta-expanded into a function.
[warn]         val nextRowUpdates = rowUpdatesSeq.next
[warn]                                            ^
[warn] one warning found
[info] compiling 4 Scala sources to /Users/ericloots/Library/Caches/com.lunatech.cmt/Courses/lunatech-scala2-to-scala3-course/target/scala-2.13/test-classes ...
org.lunatechlabs.dotty.sudoku.CellMappingSuite:
org.lunatechlabs.dotty.sudoku.ReductionRuleSuite:
  + Mapping row coordinates should result in correct column & block coordinates 0.02s
  + Mapping column coordinates should result in correct row & block coordinates 0.001s
  + Mapping block coordinates should result in correct row & column coordinates 0.001s
  + Applying reduction rules should eliminate values in isolated complete sets from occurrences in other cells (First reduction rule) 0.045s
  + Applying reduction rules should eliminate values in isolated complete sets of 5 values from occurrences in other cells (First reduction rule) 0.001s
  + Applying reduction rules should eliminate values in 2 isolated complete sets of 3 values from occurrences in other cells (First reduction rule) 0.001s
  + Applying reduction rules should eliminate values in shadowed complete sets from occurrences in the same cells (Second reduction rule) 0.001s
  + Applying reduction rules should eliminate values in shadowed complete (6 value) sets from occurrences in the same cells (Second reduction rule) 0.001s
SLF4J: A number (1) of logging calls during the initialization phase have been intercepted and are
SLF4J: now being replayed. These are subject to the filtering rules of the underlying logging system.
SLF4J: See also http://www.slf4j.org/codes.html#replay
org.lunatechlabs.dotty.sudoku.SudokuDetailProcessorSuite:
  + Sending no updates to a sudoku detail processor should result in sending a SudokuDetailUnchanged message 0.007s
  + Sending an update to a fresh instance of the SudokuDetailProcessor that sets one cell to a single value should result in sending an update that reflects this update 0.002s
  + Sending a series of subsequent Updates to a SudokuDetailProcessor should result in sending updates and ultimately return no changes 0.003s
[info] Passed: Total 11, Failed 0, Errors 0, Passed 11
[success] Total time: 5 s, completed 24 Aug 2023, 08:30:54

Observe that all (11) tests passed successfully.

Installing "The Silver Searcher"

The Silver Searcher is a command line utility that combines find and grep (and more) in a single command.

Follow the installation instructions here.

Installing an IDE

Instructions are provided in the IDE-Setup.md file in the root folder of the installed course.

lunatech-scala2-to-scala3-course's People

Contributors

Stargazers

Watchers

lunatech-scala2-to-scala3-course's Issues

Move explanation of Akka Typed in slide deck

At the end of the A recap on Scala 2 - Akka Typed - Dotty chapter, about 4 slides explain an Actor's protocol and the utilisation of message wrappers and adapters.
It's better to move these to the chapter on Union Types for two reasons:

It shortens the already quite long recap chapter
It gives information about message adapters at the moment where this is useful for solving the exercise in the chapter on Union Types

Use Pekko instead of Akka

Because Akka is not open source anymore maybe the course should use Pekko, which is the open source fork of Akka, but Pekko is not yet released.

Move code to root folder of studentified project

I find it not convenient that the sbt project is in the code folder and not in the root folder of the studentified project. I would prefer to have everything in the same folder so that I can run all the commands (git, cmtc and sbt) from the same working directory.

Amend exercise instructions to tell students to run the exercise tests

Tests were enabled by #32 . The exercise instructions should be adapted accordingly

In exercise 0, explain how to open the project in an IDE

I suggest to add a short section in exercise 0 to explain how to open the project in an IDE, and how to re-import it when the build changes.

Remove scalatest dependancy from crossDependencies

sbt-dotty plugin is used to manage dependencies that are compatible with a specific dotty version.

It is useful when your build contains dependencies that have only been published with Scala 2.x, if you have:

libraryDependencies += "a" %% "b" % "c"

you can replace it by:

libraryDependencies += ("a" %% "b" % "c").withDottyCompat(scalaVersion.value)

when compiling with Dotty this will change the cross-version to a Scala 2.x one.

ScalatTest now have artifacts published for 0.24.x and it is safe to move it out of crossDependancies and sbt will resolve it automatically based on the specified scalaVersion.

Remove workaround for ambiguous between varargs and non-varargs

CC @njlbenn
See details of workaround that needs to be removed as soon as Dotty issue #9688 is resolved

See comment for details.

Note that this workaround is applied in 4 places in the code.

No sbt auto-reload on a change of the of build definition

The build definition may change between different versions of an exercise.

In a studentified version of the course, it would be very convenient to have sbt reload the new definition automatically. This can be accomplished by adding the following setting to the global build.sbt file:

Global / onChangedBuildSource := ReloadOnSourceChanges

To support this, a new option would have to be added to the course management tools. If not, the addition of this setting will be overwritten (and discarded) when regenerating the build file via masteradm and it would also not appear in a .studentified (or linearized) version of the repo

Remove all uses of infix notation

The code still has some use cases of infix notation, for example in encoding a transformation with foldLeft:

(collection foldLeft initialValue) {
  case ...
}

The code should be scanned for these and the infix notation should be changed to dot notation.

The above would then look as follows:

collection.foldLeft(initialValue) {
  case ...
}

'cmtc install' issue on Windows

It seems that cmtc install doesn't work properly on Windows.

While investigating the issue, I found at least one issue which is that when installing for a course release on Github, the tags are retrieved using ssh protocol only. When that fails, http should be tried.

I experimented with that, but that doesn't resolve the issue. This is a bug that requires further investigation.

For the time being, the workaround is to install a course on Windows in two steps:

Download the studentified course zip archive from a released version on the course repository
Installed the course from the downloaded archive

Remove pattern guard from pattern matching expressions

Adding pattern guards on case clauses leads to the inability of the compiler to check if a pattern match is complete.
Let's remove this to illustrate how this should be done. Move the tests inside the expression executed.

studentify use instructions should be clarified

on a fresh clone of the repo lunatech-scala-2-to-scala3-course.

I have tried the following studentify -dot /home/renghen/workspace/dotty/lunatech-scala-2-to-scala3-course /home/renghen/workspace/lunatech-course

But got

YOU HAVE CHANGES IN YOUR GIT WORKSPACE. COMMIT CHANGES AND RE-RUN STUDENTIFY
Executed command: cmt-checkIfWorkspaceClean.sh /home/renghen/workspace/dotty/lunatech-scala-2-to-scala3-course
Working directory: .

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lunatech-labs / lunatech-scala2-to-scala3-course Goto Github PK

lunatech-scala2-to-scala3-course's Introduction

Moving Forward from Scala 2 to Scala 3

Description

Approach

Course installation

Install Coursier

Install a JDK

Install cmtc

Install the (Scala Center) "Scala 3 migration course"

Verifying the course installation

Install the (Lunatech) "Moving from Scala 2 to Scala 3" course

Verifying the course installation

Installing "The Silver Searcher"

Installing an IDE

lunatech-scala2-to-scala3-course's People

Contributors

Stargazers

Watchers

Forkers

lunatech-scala2-to-scala3-course's Issues

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Recommend Topics

Recommend Org

Install `cmtc`