ocaml / ocaml/dune

blang: comparisons only work with atoms

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acknowledged enhancement
Dominant language
OCaml
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Description

Hi,

Comparisons in blang (for example in enabled_if) seem to be restricted to atoms:

File "dune", line 2, characters 16-31:
2 |  (enabled_if (= (and true true) true))
                    ^^^^^^^^^^^^^^^
Error: Unexpected list

The AST looks to be designed that way:

https://github.com/ocaml/dune/blob/2a469ef2487bbb7e58736958dad54f3ceb11871c/src/dune_rules/blang.ml#L33-L38

It looks like it could be extended.

cc @snowleopard

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading src/dune_rules/blang.ml around the AST definition linked in the issue, then reproduce the enabled_if example in a small dune file. Extend the comparison handling so the shown expression is accepted, and verify that the example no longer reports Unexpected list.

Written by the indexing model from the issue text.

Assessment

Tech stack
ocaml
Domain
build-system
Issue type
Feature
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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