Replace every use of ErrorCall with a custom Exception value

[jwiegley]

Rather than pass strings with rendered components to ErrorCall, every possible error or piece of information raised within hnix should use a specific constructor, retaining as much information as possible about the context of that information.

[Anton-Latukha]

I want to do this task on a long time basis. Until the code is covered.

TL;DL: What is the stabilized module that would be easier/better for me to start with?

My current level

I have solid basic Haskell knowledge: study repo (there are literally all exercises from the chapters, done and commented by myself), and my theory dictionary.

I am interested to get deeper in error handling to master it. I know we would choose only particular ways of handling.

I can also do QuickCheck testing. I understand the problematics and limits of property-testing, generators and shrinking. Able to use library classes or write custom generators, properties, and abstract around them. If other testing tools are chosen - I would be eager to learn them also.

I love diving into mathematical theories around Haskell as also philosophy and etymology. I love to understand things I know pretty deep.

You can freely use terminology in directions to my work. That way I would understand directly, and you would also help me.

The task

So you request code to have data type constructors for errors.

As I understand it also would go great with smart constructors to weed-out Error cases from the normal flow.

What is the stabilized module that would be easier/better for me to start with?

_{P.S. I am a sort of fan of yours, because walking my life I found numerous times I walk with the help of your work, your posts, and with your Elisp code, and with the help of org-habit I changed&changing my life to better.}

[Anton-Latukha]

Oh, about Nix.
I once wrote new Nix installer (NixOS/nix#1565), that is despite all my efforts is not merged still.
And I am a temperate contributor and maintainer of a couple of packages in NixPkgs: NixOS/nixpkgs#59293.
And also worked as Nix/NixOS/NixOps/Hydra DevOps.
So for Nix language, and processes/terms I also have some understanding, that would allow me during work better and better understand the hnix code base.

[Anton-Latukha]

Related: #760 (comment)

[Anton-Latukha]

Since PR desynced & closed it - task is no longer in the process - report is open to contribution.

If someone would attend to the task - please, because the error handling in Haskell is a developing & pluralism topic - lets start public dialog about it in advance to settle on a way. & since the amount of changes is big - I promise to try to accept stages/parts of the work done.

[Anton-Latukha]

I think that Frames structure should be understood, documented and it is lacking somewhere - it needs to complete own functionality. Then spread over the code, on appropriate levels, to cover the code. Then there we would arrive to what this report asks. & even now I do not understand completely what mechanism is asked/implied.