Tracking issue for missing features

[Nadrieril]

Dhall spec

• parsing
  • nullary union constructors Handle unions with nullary alternatives (https://github.com/dhall-lang/dhall-lang/pull/438) #36
  • selection by expression Record projection by expression #94
  • toMap toMap keyword #96
  • inline headers
  • RFC3986 URLs Parse RFC3986 URLs #136
  • everything else
• imports
  • import cycles Handle import cycles #8
  • import alternatives Handle import alternatives #70
  • import canonicalization Canonicalization of imports #76
  • remote imports Handle remote imports, first without sanity checks #10
  • sanity check in remote imports Implement a bunch of missing features #139
  • headers in remote imports Support custom import headers #134
  • checksums Support import caching and hashing #135
  • as Location Implement a bunch of missing features #139
  • ...
• typechecking
  • text interpolation
  • higher-kinded records
  • unions
  • Integer/show
  • Natural/show
  • Double/show
  • Natural/toInteger
  • #, aka ListAppend
  • Text/show
  • //\\, aka CombineTypes and RecursiveRecordTypeMerge Implement Type Check for //\\ #91
  • /\, aka Combine and RecursiveRecordMerge Implement Type Check for /\ #89
  • //, aka Prefer and RightBiasedRecordMerge Implement Type Check for // #86
  • record projection (record.{ x, y, z })
  • union constructor selection (union.x)
  • nullary union constructors Handle unions with nullary alternatives (https://github.com/dhall-lang/dhall-lang/pull/438) #36
  • merge
  • duplicate record fields
  • selection by expression Record projection by expression #94
  • toMap toMap keyword #96
  • ...
• normalization
  • text interpolation
  • Integer/show
  • Natural/show
  • Double/show
  • Natural/toInteger
  • #, aka ListAppend
  • Text/show
  • //\\, aka CombineTypes and RecursiveRecordTypeMerge
  • /\, aka Combine and RecursiveRecordMerge
  • //, aka Prefer and RightBiasedRecordMerge
  • record projection (record.{ x, y, z })
  • union constructor selection (union.x)
  • nullary union constructors Handle unions with nullary alternatives (https://github.com/dhall-lang/dhall-lang/pull/438) #36
  • various simplifications
  • simplifications that use equivalence
  • selection by expression Record projection by expression #94
  • Normalize field selection further by inspecting the argument Implement a bunch of missing features #139
  • toMap toMap keyword #96
  • ...
• alpha-normalization Implement alpha-normalization #12
• binary decoding
• binary encoding Binary encoding #39

Pretty error messages

• parsing
  • show error location in source file
  • explain the error in words
• import
• typecheck
  • basic legible error message Implement Display for TypeError #63
  • show error location in source file Tracking issue for great error messages #40
• binary decoding
• explain the cause of error in the global Error type

Public API

• control import resolution
• deserialize from file
• settle lifetime behaviour in expr lifecycle
• documentation
  • document nightlyness
  • deserialization functions
  • expression lifecycle
  • ...
• publish to crates.io Publish to crates.io #74
• split the public API into a separate crate

[FintanH]

Hey @Nadrieril is there any low hanging fruit where I could get started here? I'm new to Rust, but familiar with Dhall and have contributed to the language and Haskell implementation. Willing to get my hands dirty here 🙇

[Nadrieril]

Hey @FintanH ! Thanks for your interest in this project ! I'm glad you're willing to get your hands dirty because this project is quite a mess ^^
I can't see anything very low-hanging sadly. Would you be interested in trying one of the missing typechecking cases, say right-biased record merge for example ? I think it could make a nice mini-project

[FintanH]

Ya, I can give it a shot! :)

[Nadrieril]

Yay ! Could you open an issue about that feature ? Then over there you can bombard me with questions about the structure of the project, where the different bits are, how Values and Thunks work, or anything else you need. I'll try to answer as much as I'm able to.
As a start I'd recommend you try to break something in typecheck.rs and run cargo test, to help you get an idea of the thing.

[Nadrieril]

@basile-henry: if you're interested too, you're welcome to try recursive record merge for example. Just open an issue too and ask away !

[basile-henry]

@Nadrieril I might have a go at recursive record merge this weekend if no one has started working on that by then! 😄

[FintanH]

You can link the issue to the checklist if you want now :) #86

[FintanH]

I've created an issue for Combine #89. @basile-henry Did you start work on it? If not I could get cracking on it.

[basile-henry]

@FintanH I did start working on it but I didn't get very far. The codebase has changed quite a bit since last time I looked at it and I was struggling to find all the pieces I needed.
Feel free to take it over, you probably know more than I do about how everything fits together by now.
This is what I started doing, it's still very incomplete but maybe it'll help you getting started on that one: basile-henry@3b49079

[FintanH]

@Nadrieril I'm feeling some momentum after putting up those PRs for typechecking. What would make the most sense for working on next? 😁

[Nadrieril]

@FintanH :D
Let's see... The missing features are essentially about imports. There's a lot to do: we barely support local imports. You can pick what you want in there: remote imports, environment variables, checksums, import alternatives, ... Import alternatives may require some tinkering with the overengineered mess I made around ExprF, so you probably want to avoid that until I sort out the mess; the rest should be fine.

[FintanH]

I was thinking import would be next too. I'll do up some tickets and do some digging!

[Nadrieril]

There's a new feature to implement: projection by expression (#94) ! There's everything from parsing to typechecking left to implement, if anyone's interested

[Nadrieril]

@basile-henry @FintanH I've given both of you merge rights to this repo, so that you can merge your own PRs yourselves :). Here is what I propose: you can merge a PR yourself after I've approved it, or otherwise if I haven't approved or disapproved for 7 days you can go ahead and merge it (like what's done in dhall-lang). Mistakes are easy to fix, so we may as well err on the side of making things happen.

[FintanH]

Ya that sounds great. Thanks!

[Nadrieril]

I wrote one or two good first issues if anyone is interested :)

[Nadrieril]

Now that most features are done, I'm closing this in favor of labeled issues https://github.com/Nadrieril/dhall-rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc+label%3Astandard-compliance