If you are a Wasp user and not a contributor (yet :)), you might want to look into following resources instead ([**Project page**](https://wasp-lang.dev), [**Docs**](https://wasp-lang.dev/docs)).
If you would like to make your first contribution, here is a handy checklist we made for you:
- [ ] Read [Quick overview](#quick-overview).
- [ ] Compile the project successfully and get todoApp example running (follow [Basics](#basics)).
- [ ] Join [Discord](https://discord.gg/rzdnErX) and say hi :)!
- [ ] Pick an issue [labeled with "good first issue"](https://github.com/wasp-lang/wasp/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22) and let us know you would like to work on it - ideally immediatelly propose a plan of action and ask questions.
If you can't find a suitable issue for you, reach out to us on Discord and we can try to find smth for you together.
- [ ] Make a PR and have it accepted! Check [Typical workflow](#typical-development-workflow) for guidance, and consult [Codebase overview](#codebase-overview) for more details on how Wasp compiler works internally.
## Quick overview
Wasp compiler is implemented in Haskell, but you will also see a lot of Javascript and other web technologies because Wasp compiler transpiles Wasp code into them.
You don't have to be expert in Haskell to contribute or understand the code, since we don't use complicated Haskell features much -> most of the code is relatively simple and straight-forward, and we are happy to help with the part that is not.
Main result of building the project is `wasp` executable (also reffered to as CLI), which is both Wasp compiler, CLI and Wasp project runner in one - one tool for everything Wasp-related.
`wasp` executable takes `.wasp` files and `ext/` dir as input and generates a web app from them.
It can then also run that web app for you, deploy it (not yet but that is coming), and manage it in other ways.
This might take a while (10 mins) if you are doing it for the very first time, since `cabal` will need to download the external dependencies.
If that is the case, relax and feel free to get yourself a cup of coffee! When somebody asks what you are doing, you can finally rightfully say "compiling!" :D.
2. If you don't have a good/reliable working HLS (Haskell Language Server) in your IDE, you will want to instead run `./run ghcid` from the root of the project instead: this will run a process that watches the Haskell project and reports any Haskell compiler errors. Leave it running.
NOTE: You will need to install `ghcid` globally first. You can do it with `cabal install ghcid`.
4. Once close to done, run `cabal test` to confirm that the project's tests are passing (both new and old).
5. If needed, confirm that `examples/todoApp/` is working correctly by running `cabal build` first, to build the wasp executable, and then by running that executable with `cabal run wasp-cli start` from the `examples/todoApp/` dir -> this will run the web app in development mode with the current version of your Wasp code.
You can do this by running `cabal freeze` to use the existing frozen dependencies while also capturing new changes you did -> you will likely want to do this if you added a new dependency and don't want to touch frozen versions of other dependencies.
Or, you can completely recreate freeze file by running `rm cabal.project.freeze && cabal freeze` (or `./run refreeze`) -> you will likely want to do this if you want to get updates for packages, or if just running `cabal freeze` is too restricted by versions currently captured in freeze file.
If not sure what to do, it is easiest and always ok to just do `./run refreeze`.
8. If your PR changes how users(Waspers) use Wasp, make sure to also create a PR that will update the documentation, which is in a [separate repo](https://wasp-lang.dev/docs/tutorials/getting-started).
10. Reviewer will merge the branch into `main`. Yay!
NOTE: What is cabal freeze file, what is its purpose?
Freeze file (`cabal.project.freeze`) plays the same role as `package.lock.json` in `npm` -> it enables reproducible builds.
What `cabal freeze` does is, it captures exact versions of all the cabal dependencies (recursively) used at the moment and writes them down into `cabal.project.freeze` file. Then, in future, `cabal` uses those versions for any commands it runs, regardless of what is written in `.cabal` file.
This ensures consistent builds accross CI and different development machines -> a dependency won't suddenly get updated because the patch was released (potentially causing a bug).
The way to think about .cabal vs cabal.project.freeze is that dependency version bounds in .cabal specify what range of dependencies are we ok with, while freeze file specifies what (in that range) we know worked last and we tested with.
If the feature you are implementing is complex, be it due to its design or technical implementation, we recommend creating a [design doc](https://www.industrialempathy.com/posts/design-docs-at-google/) (aka RFC).
It is a great way to share the idea you have with others while also getting help and feedback.
To create one, make a PR that adds a markdown document under `wasp/docs/design-docs`, and in that markdown document explain the thinking behind and choice made when deciding how to implement a feature.
Others will comment on your design doc, and once it has gone through needed iterations and is approved, you can start with the implementation of the feature (in a separate PR).
Wasp file(s) are analyzed by Analyzer, where they are first parsed, then typechecked, and then evaluated into a central IR (Intermediate Representation), which is `AppSpec` (`src/Wasp/AppSpec.hs`).
Generated web app consists of client, server and database.
Client is written with React and react-query.
Server is written in NodeJS and uses ExpressJs.
Database is abstracted via Prisma.
We can run Wasp project with `wasp start`.
This will first compile the app, generate JS code in the `.wasp/out/` dir, and then run `npm start` for the client, `npm start` for the server, and also run the database.
On any changes you do to the source code of Wasp, Wasp project gets recompiled, and then changes in the generated code are picked up by the `npm start` of the client/server, therefore updating the web app.
-`cabal update` to update your package information.
-`cabal build` to build the project, including `wasp` binary which is both CLI and compiler in one.
-`cabal run wasp-cli <arguments>` to run the `wasp` binary that was previously built.
-`cabal test` to build the whole project + tests and then also run tests.
-`cabal install` -> builds the project and places the binary so it is in PATH (so you can call it directly, from anywhere, with just `wasp`).
For live compilation and error checking of your code we recommend using Haskell Language Server (hls) via your IDE, but if that is not working as it should, then safe fallback is always `ghcid`. You can install `ghcid` globally with `cabal install ghcid` and then just type `ghcid` when in the project -> it will watch for any file changes and report errors.
For tests we are using [**Tasty**](https://documentup.com/feuerbach/tasty) testing framework. Tasty let's us combine different types of tests into a single test suite.
In Tasty, there is a main test file that is run when test suite is run. In that file we need to manually compose test tree out of tests that we wrote. We organize tests in test groups, which are then recursively grouped resulting in a test tree.
Tests are normally split in files of course, so we need to import those all the way up to the main test file, however we organize our test groups/trees.
In order to avoid need for manual organization and importing of test files described above, we are using [tasty-discover](https://hackage.haskell.org/package/tasty-discover) which does this for us.
It automatically detects files containing tests and organizes them for us into a test tree (and also takes care of importing).
This means we only need to create a file, write tests in it and that is it.
Test functions however do need to be prefixed with special prefix to indicate which type of test are they: spec_ for Hspec, prop_ for QuickCheck and similar.
We can however still organize tests manually if we want in Tasty test trees, and then we just prefix them with test_ and tasty-discover will pick them up from there.
This is convention for Haskell, opposite to mixing them with source code as in Javascript for example.
Not only that, but Haskell build tools don't have a good support for mixing them with source files, so even if we wanted to do that it is just not worth the hassle.
To run unit tests only, you can do `cabal test waspc-test` (or `./run test:unit`).
To run individual unit test, you can do `cabal test waspc-test --test-options "-p \"Some test description to match\""` (or just `./run test:unit "Some test description to match"`).
This will build the codebase, run stan on it (while installing it first, if needed, with the correct version of GHC) and then write results to the CLI and also generate report in the `stan.html`.
We also wrote a `new-release` script which you can use to help you with creating new release: you need to provide it with new version (`./new-release 0.3.0`) and it will update the version in waspc.cabal, commit it, push it, and will also create appropriate tag and push it, therefore triggering CI to create new release on Github.
External documentation, for users of Wasp, is hosted at https://wasp-lang.dev/docs, and its source is available at [web/docs](/web/docs), next to the website and blog.
When writing a TODO or NOTE, use all capital letters, like this:
```hs
-- TODO: Wash the car.
-- NOTE: This piece of code is slow.
```
If you wish, you can add your name to TODO / NOTE. This is useful if you think there is a fair chance that reader of that TODO / NOTE might want to consult with its author.
You can do it like this:
```hs
-- TODO(martin): Doesn't work on my machine in some unusual use cases.
