DEV Community

Cover image for Learning ReasonML The Hard Way
Alain
Alain

Posted on • Edited on

Learning ReasonML The Hard Way

#reason #ocaml #bashscripts #github

Learning to Code by Reading Code

I have this riduculous process for figuring things out with reasonml. Basically it entails trying to do something, hitting a wall. Hitting the docs for whatever code I am trying to use, then rummaging around Github for some code that implements what I am trying to do.

A lot of the time, that code is in old reasonml syntax or in ocaml. I end up learning the ocaml, converting it to reasonml or often times, updating old projects until they work again.

Today, for example, I discovered Iwan Karamazow's git repos. Had to know what his 4 year old transducers.re was about. So I forked and updated it until it compiled. I still can't figure out how to call the functions and asked him about it. We will see if he is still interested in it. That led me to some more old code demonstrating transducers in @oddlyfunctional's oddlyfunctional/bs-transducers, which then sent me to to his 2 year old
form-builder-reasonml repo which is the subject of this code study today.

Thank you to Iwan and Mario for sharing their transducers!

Here We Go!

This code is super old so we are going to have to lean on bloodyowl/upgrade-reason-react-esy.

Let clone, fork, download the target repo to get started.

git clone https://github.com/oddlyfunctional/form-builder-reasonml old-code-update
Enter fullscreen mode Exit fullscreen mode

Let's follow the not to heavy upgrade-reason-react-esy README instructions.

  1. npm i bloodyowl-upgrade-reason-react.

Trying to install fails. I am guessing its because of some package-lock.json dependency.

Lets rm package-lock.json to get rid of the old dependencies interfering. I am also going to get rid of the node,grpc@1.13.1, node-pre-grp and bs-platform@4.0.7 files since, first, why are they there?, and second,not the point of what we are doing here.

Lets run:

rm package-lock.json node grpc@1.13.1 node-pre-grp bs-platform@4.0.7
Enter fullscreen mode Exit fullscreen mode

Try installing again, npm install. This takes a while because it has to build grpc@1.13.1. Installing fails again because the project requires node 10.x listed in engines in package.json. I am using fnm so I will add the expected version with fnm install 10 the set it on this directory with fnm use 10.

Run npm install again and it works.

Try installing the upgrade package again and it works:

> npm i bloodyowl-upgrade-reason-react
Enter fullscreen mode Exit fullscreen mode

Next we will run find src -name "*.re" | yarn Upgrade as per the docs.

Here is the output if you run the command, but don't just yet:

~/Github/old-code-update updating* 21s
❯ find src -name "*.re" | yarn Upgrade
yarn run v1.22.4
$ /Users/mandalarian/Github/old-code-update/node_modules/.bin/Upgrade
 UpgradeRR  Done  src/AlternateChoices.re
 UpgradeRR  Done  src/Answer.re
 UpgradeRR  Done  src/AnswerDB.re
 UpgradeRR  Done  src/App.re
 UpgradeRR  Done  src/AppContext.re
 UpgradeRR  Done  src/Authenticated.re
 UpgradeRR  Done  src/Context.re
 UpgradeRR  Done  src/EditQuestionnaire/EditQuestionnaire.re
 UpgradeRR  Done  src/EditQuestionnaire/QuestionField.re
 UpgradeRR  Done  src/EditQuestionnaire/SelectQuestionType.re
 UpgradeRR  Done  src/EditQuestionnaire/TextInput.re
 UpgradeRR  Done  src/Firebase.re
 UpgradeRR  Done  src/FirebaseAuth.re
 UpgradeRR  Done  src/Form.re
 UpgradeRR  Done  src/Index.re
 UpgradeRR  Done  src/Link.re
 UpgradeRR  Done  src/ListQuestionnaires.re
 UpgradeRR  Done  src/MultipleChoices.re
 UpgradeRR  Done  src/QuestionnaireDB.re
 UpgradeRR  Done  src/Router.re
 UpgradeRR  Done  src/SharedTypes.re
 UpgradeRR  Done  src/ShowQuestionnaire.re
 UpgradeRR  Done  src/ShowQuestionnaireAnswers.re
 UpgradeRR  Done  src/Styles.re
 UpgradeRR  Done  src/TextArea.re
 UpgradeRR  Done  src/TextField.re
 UpgradeRR  Done  src/Utils.re
Done!
✨  Done in 0.72s.

~/Github/old-code-update updating*
❯
Enter fullscreen mode Exit fullscreen mode

Instead of outputing the result to the terminal, let's run it and push the output to a file:

❯ find src -name "*.re" | yarn Upgrade > edits.cfg
Enter fullscreen mode Exit fullscreen mode

It should look something like:

yarn run v1.22.4
$ /Github/old-code-update/node_modules/.bin/Upgrade
 UpgradeRR  Done  src/AlternateChoices.re
 UpgradeRR  Done  src/Answer.re
 UpgradeRR  Done  src/AnswerDB.re
 UpgradeRR  Done  src/App.re
 UpgradeRR  Done  src/AppContext.re
 UpgradeRR  Done  src/Authenticated.re
 UpgradeRR  Done  src/Context.re
 UpgradeRR  Done  src/EditQuestionnaire/EditQuestionnaire.re
 UpgradeRR  Done  src/EditQuestionnaire/QuestionField.re
 UpgradeRR  Done  src/EditQuestionnaire/SelectQuestionType.re
 UpgradeRR  Done  src/EditQuestionnaire/TextInput.re
 UpgradeRR  Done  src/Firebase.re
 UpgradeRR  Done  src/FirebaseAuth.re
 UpgradeRR  Done  src/Form.re
 UpgradeRR  Done  src/Index.re
 UpgradeRR  Done  src/Link.re
 UpgradeRR  Done  src/ListQuestionnaires.re
 UpgradeRR  Done  src/MultipleChoices.re
 UpgradeRR  Done  src/QuestionnaireDB.re
 UpgradeRR  Done  src/Router.re
 UpgradeRR  Done  src/SharedTypes.re
 UpgradeRR  Done  src/ShowQuestionnaire.re
 UpgradeRR  Done  src/ShowQuestionnaireAnswers.re
 UpgradeRR  Done  src/Styles.re
 UpgradeRR  Done  src/TextArea.re
 UpgradeRR  Done  src/TextField.re
 UpgradeRR  Done  src/Utils.re
Done!
Done in 0.34s.
Enter fullscreen mode Exit fullscreen mode

Doing this will let us be a little more effecient with some terminal scripts later.

Updating Strings

@bloodyowl again:

If you've alias ReasonReact to React, search and replace it back to ReasonReact.

Search and replace:

ReasonReact.Update to Update

ReasonReact.UpdateWithSideEffects to UpdateWithSideEffects

ReasonReact.SideEffects to SideEffects

ReasonReact.NoUpdate to NoUpdate

This seems a bit error prone to redo these steps every time I am up in some random old repo so I wrote this little hack using this awesome random library I came across in my random reason project meandering. Its called FastReplaceString by some hacker named Iwan Karamazow who seems to have been active in the early reason days. Thanks again, Iwan!

Let's install his utiility:

npm i -D IwanKaramazow/FastReplaceString
Enter fullscreen mode Exit fullscreen mode

Lets create a script called reasonreactupdate.sh and put this in it:

#!/bin/zsh
# get our filelist
file=edits.cfg

# define a function with the changes we want to make and call `fastreplacestring.exe` on each version of tuple
function edits(){
  for i in "ReasonReact.Update Update" "ReasonReact.NoUpdate NoUpdate" "ReasonReact.UpdateWithSideEffects UpdateWithSideEffects"
do
    set -- $i
    echo fastreplacestring.exe $1 $2
done
};

while IFS= read -r cmd; do
    edits $cmd
done < "$file"
Enter fullscreen mode Exit fullscreen mode

So what are we doing? Instead of searching for each set of string in our editor we will iterate over tuples of the edits we want to make calling each variation of what bloodyowl wants us to do with fastreplacestring. For example, the first tuple is

("ReasonReact.Update Update")
Enter fullscreen mode Exit fullscreen mode

So the script will go through and change all the instances of the left side, to the right side of the tuple. Or the first argument to the second argument.

Just for for fun, if you are in a situation where you have aliased the ReasonReact as React we can just run both changes on all the affected files. I put each variation in a different script to keep my mind from going crazy.

# reactupdate.sh handles getting rid of the aliases
file=edits.cfg
function edits(){
  for i in "React.Update ReasonReact.Update" "React.NoUpdate ReasonReact.NoUpdate" "React.UpdateWithSideEffects ReasonReact.UpdateWithSideEffects"
do
    set -- $i
    echo fastreplacestring.exe $1 $2
done
};

while IFS= read -r cmd; do
    edits $cmd
done < "$file"
Enter fullscreen mode Exit fullscreen mode

Then in ./replacestrings.sh we will do:

#!/bin/zsh

./reactupdate.sh; 
./reasonreactupdate.sh
Enter fullscreen mode Exit fullscreen mode

So whether you had used an alias or not, everything gets handled.

Running it looks like this:

~/Github/old-code-update updating*
❯ ./replacestrings.sh
# running reactupdate.sh ...for every file
fastreplacestring.exe React.Update ReasonReact.Update
fastreplacestring.exe React.NoUpdate ReasonReact.NoUpdate
fastreplacestring.exe React.UpdateWithSideEffects ReasonReact.UpdateWithSideEffects

# ...running reasonreactupdate.sh for every file
fastreplacestring.exe React.Update ReasonReact.Update
fastreplacestring.exe React.NoUpdate ReasonReact.NoUpdate
fastreplacestring.exe React.UpdateWithSideEffects ReasonReact.UpdateWithSideEffects

# ...abbreviated to save your eyes
~/Github/old-code-update updating*
❯
Enter fullscreen mode Exit fullscreen mode

Updating ReasonReact

Install reason-react from this fork's master branch.

Now we need to install a specific version of reason-react as indicated by the docs along with two more @bloodyowl libs,reason-react-update and reason-react-compat. These will allow us to keep using the old ReasonReact api the project.

Needless to say, @bloodyowl is a boss.

Run:

npm i https://github.com/bloodyowl/reason-react 
npm i reason-react-update reason-react-compat
Enter fullscreen mode Exit fullscreen mode

Change JSX version in bsconfig.json 

 "reason": {
-  "react-jsx": 2
+  "react-jsx": 3
 },
Enter fullscreen mode Exit fullscreen mode

Now you can start the project with npm start. What I saw was the following error:

❯ yarn start
yarn run v1.22.4
$ bsb -make-world -w
File "bsconfig.json", line 5:
Error: JSX version 3 is deprecated, please downgrade to 1.x for version 3 
For more details, please checkout the schema http://bucklescript.github.io/bucklescript/docson/#build-schema.json
>>>> Start compiling
Enter fullscreen mode Exit fullscreen mode

We already changed the react-jsx so why is it complaining? I had not seen this in a while so I had to jump back into the absolutely essential reasonml-discord channel and search for it.

This has something to do with the version of reason-react we are using.

I know the solution is to add the latest version of reason-react but I'm mildly conflicted about whether I should handle the next line in the docs first.

Update places where you use DOM refs (whether use React.createRef or React.useRef above your components).

I just searched for useRef and createRef in the project and found nothing so I'm just going to go ahead and install reason-react@latest.

npm i reason-react@latest
Enter fullscreen mode Exit fullscreen mode

Didn't work:

~/Github/old-code-update2 updating*
❯ yarn start               
yarn run v1.22.4
$ bsb -make-world -w
File "bsconfig.json", line 5:
Error: JSX version 3 is deprecated, please downgrade to 1.x for version 3 
For more details, please checkout the schema http://bucklescript.github.io/bucklescript/docson/#build-schema.json
>>>> Start compiling
Enter fullscreen mode Exit fullscreen mode

Then I see:

"bs-platform": "^4.0.7",
Enter fullscreen mode Exit fullscreen mode

in package.json and realise we have to update that too.

Run npm i bs-platform@latest and we are back in business:

~/Github/old-code-update2 updating*
❯ yarn start              
yarn run v1.22.4
$ bsb -make-world -w
[37/37] Building src/ReactDOMRe.cmj
[15/15] Building src/Json.cmj
[8/8] Building src/Css.cmj
[5/5] Building src/jest.cmj
[14/14] Building src/DomTestingLibrary.cmj
[5/5] Building src/ReactTestingLibrary.cmj
>>>> Start compiling
Enter fullscreen mode Exit fullscreen mode

Working Through Errors

The first error we see is knuckleheadish: Error: Unbound module ReactCompat.

When we installed the two libs, reason-react-compat and reason-react-update I forgot to add them to bsconfig.json. I used to have a script in my dotfiles that handled this, then I accidently deleted them. And now thanks to learning in public, I figured I should go ahead and figure it out again so you can use it too.

# script to add dependency to `packag.json.dependecies` and `bsconfig.[bs-dependencies]`
function _add_bs_dependency(){

  NEWDEP=$1
  npm install $NEWDEP

  $(cat bsconfig.json | jq --arg NEWDEP $NEWDEP -r '.["bs-dependencies"] 
 += [$NEWDEP]' | sponge bsconfig.json)

  cat bsconfig.json | jq '.["bs-dependencies"]'
  echo ✨${NEWDEP} added to bs-dependencies ✨
}
Enter fullscreen mode Exit fullscreen mode

I am so happy to have this script back. One command to install a bs-dependency.

Stick that in your dotfiles and run addbs reason-react-compat and addbs reason-react-update.

You should get back:

❯ addbs reason-react-update
[
  "reason-react",
  "@glennsl/bs-json",
  "bs-css",
  "reason-react-compat",
  "reason-react-update"
]
✨reason-react-update added to bs-dependencies ✨
Enter fullscreen mode Exit fullscreen mode

I should really figure out how to make the script take multiples args...

ReasonReact.Compat

After restarting the project we should be getting a bunch of errors referrencing

  ReactCompat.useRecordApi({
    ...component,
Enter fullscreen mode Exit fullscreen mode

We must hit the reason-react-compat docs here. There is a path to upgrading so lets follow it. We need to change all instances of ...component, to ...ReactCompat.component. Wait, those are strings! I wonder if FastReplaceString can handle it. Better yet, I just remembered I have replace script. Let's try it.

We could try running:

# outputs just list of places where our string shows up and pipes it to faststring replace
grep -rnwl 'src' -e '...component'  | fastreplacestring.exe "...component" "...ReactCompat.component"
Enter fullscreen mode Exit fullscreen mode

But it needs some tweaking to work.

This is the replace script:

#!/bin/sh
#
# Find and replace by a given list of files.
#
# replace foo bar **/*.ml
# https://thoughtbot.com/blog/sed-102-replace-in-place

find_this="$1"
shift
replace_with="$1"
shift

if command -v rg &>/dev/null ; then
  items=$(rg -l --color never "$find_this" "$@")
else
  items=$(ag -l --nocolor "$find_this" "$@")
fi

temp="${TMPDIR:-/tmp}/replace_temp_file.$$"
IFS=$'\n'
for item in $items; do
  sed "s/$find_this/$replace_with/g" "$item" > "$temp" && mv "$temp" "$item"
done
Enter fullscreen mode Exit fullscreen mode

Running replace "...component" "...ReactCompat.component" works fantastically.

Well that's it for now, folks. I can't promise I will finish this update because I got what I needed from it.

This has been learning in public.

UDPATE

If you want a better understanding of this, check out this post I had missed previously from @bloodyowl => migrating-a-large-reason-plus-react-codebase-to-hooks.

Top comments (2)

Collapse
 
sophiabrandt profile image
Sophia Brandt •

Wow, what an insane journey. Your approach seems bonkers (in a good way).

Thanks for sharing. 🌷🌷🌷

Collapse
 
idkjs profile image
Alain •

It is bonkers! I need some structure to get focused. If not, I dive deep into whatever thing I find next. Old, update it. Dead dep? Find a new one. Command doesn't run, why not? Learned a whole lot that way, but structure would be better, no! Something you have in abundance.

Peace to you, sister. Keep sharing the love!

Read next

meotism profile image

Day before an interview how I prepare

meotism -

ajay_tainwala profile image

🚀 Unlock Free AI and Cloud Skills with Microsoft’s Free Courses

Ajay Tainwala -

pradumnasaraf profile image

Publishing Multi-Arch Docker images to GHCR using Buildx and GitHub Actions

Pradumna Saraf -

thisisthedeveloper profile image

Understanding CI/CD: A Comprehensive Guide

Chandra Prakash Tekwani -