Conditional configuration & environment

[KtorZ]

Context

Closes #937.

Preview

☝️ Many things happening on the image above:

• The project defines a bunch of environments under the env directory.
• The project defines an extra set of configurations in its aiken.toml
• Tests make use of the special env and config modules, which are populated based on the --env flag. Defaulting to the environment/config called default when not present.
• Tests are making conflicting assertions which can only pass in one of the given environment. As illustrated, since --env preprod is passed, only the preprod tests pass.

No default environment?

Unknown environment?

Completely unknown	Close enough

Missing configuration?

Note

This only triggers a warning because it may not be problematic should the configuration be unused. If it is used, we simply fallback to a usual 'unknown module' error.

Changelog

• 📍 Parse sources of conditional env modules.
  Do nothing about it yet, but trigger an error if env/default.ak is
  missing; but only if there's any module at all under env.

• 📍 Thread down environment module from cli down to the type-checker
  We simply provide a flag with a free-form output which acts as
  the module to lookup in the 'env' folder. The strategy is to replace
  the environment module name on-the-fly when a user tries to import
  'env'.

  If the environment isn't found, an 'UnknownModule' error is raised
  (which I will slightly adjust in a following commits to something more
  related to environment)

  There are few important consequences to this design which may not seem
  immediately obvious:

  1. We parse and type-check every env modules, even if they aren't
     used. This ensures that code doesn't break with a compilation error
     simply because people forgot to type-check a given env.

     Note that compilation could still fail because the env module
     itself could provide an invalid API. So it only prevents each
     modules to be independently wrong when taken in isolation.

  2. Technically, this also means that one can import env modules in
     other env modules by their names. I don't know if it's a good or
     bad idea at this point but it doesn't really do any wrong;
     dependencies and cycles are handlded all-the-same.

• 📍 Ensure env modules dependencies are properly handled.
  We figure out dependencies by looking at 'use' definition in parsed
  modules. However, in the case of environment modules, we must consider
  all of them when seeing "use env". Without that, the env modules are
  simply compiled in parallel and may not yet have been compiled when
  they are needed as actual dependencies.

• 📍 Create dedicated error when environment isn't found.
  This is less confusing that getting an 'UnknownModule' error reporting
  even a different module name than the one actually being important
  ('env').

  Also, this commit fixes a few errors found in the type-checker
  when reporting 'UnknownModule' errors. About half the time, we would
  actually attached imported modules instead of importable modules
  to the error, making the neighboring suggestion quite worse (nay
  useless).

• 📍 Allow simple expressions as configuration in aiken.toml
  This is currently extremely limited as it only supports (UTF-8)
  bytearrays and integers. We should seek to at least support hex bytes
  sequences, as well as bools, lists and possibly options.

  For the latter, we the rework on constant outlined in Hoist complex constant #992 is
  necessary.

• 📍 Allow bytes to be defined as plain strings, or with specified encoding.
  The syntax is as follows:

  { "bytes" = "...", "encoding" = "" }

  The following encoding are accepted:

  "utf8", "utf-8", "hex", "base16"

  Note: the duplicates are only there to make it easier for people to
  discover them by accident. When "hex" (resp. "base16") is specified,
  the bytes string will be decoded and must be a valid hex string.

• 📍 Fill-in CHANGELOG.

[rvcas]

Excellent, this is so epic

[rvcas]

Very cool

[rvcas]

I don't know if you want to merge this yet, seems ready to me but I'll let you click the button.