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Compatibility: web-cssom-view 0.1.0 drops scrollIntoView options through purs-specific FFI

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Active
Tech stack
javascript, node.js, rust
Domain
compilers, devtools

Research direction

Start with src/Web/CSSOMView/Element.js, especially the scrollIntoViewOptions handling at lines 17–27, then inspect src/Main.purs and src/Main.js. Run the stated spago build and iris build reproductions in separate output trees and compare the generated calls; done means the compiler-versus-package ownership and compatibility policy are resolved.

Written by the indexing model from the issue text.

Description

This tracks a package FFI compatibility mismatch, not an established Iris compiler bug. purescript-web/[email protected] reads purs-generated .value0 and enum .constructor.name in src/Web/CSSOMView/Element.js. Iris 0.1.1 uses a different valid representation for Maybe, so a Just options argument silently takes the no-argument branch. The broader upstream concern is purescript-web/purescript-web-cssom-view#7; this tracker currently has no issue for the concrete cross-compiler symptom. The upstream repository is read-only to this account, so I could not add the reproducer there.

Standalone repro with registry package set 81.1.0, web-cssom-view 0.1.0, purs 0.15.15 / Iris 0.1.1, Node 22.16.0:

spago.yaml:

package:
  name: cssom-view-repro
  dependencies:
    - prelude
    - effect
    - console
    - maybe
    - web-dom
    - web-cssom-view
workspace:
  packageSet:
    registry: 81.1.0

src/Main.purs:

module Main where

import Prelude
import Data.Maybe (Maybe(..))
import Effect (Effect)
import Effect.Console (log)
import Web.CSSOMView as View
import Web.CSSOMView.Element as Scroll
import Web.DOM.Element (Element)

foreign import element :: Element
foreign import calls :: Effect (Array String)

main :: Effect Unit
main = do
  Scroll.scrollIntoView Nothing element
  Scroll.scrollIntoView (Just { block: View.End, inline: View.Nearest, behavior: View.Smooth }) element
  log <<< show =<< calls

src/Main.js (synthetic host; this checks FFI delivery, not browser geometry):

const seen = [];
export const element = {
  scrollIntoView(...args) { seen.push(JSON.stringify(args)); }
};
export const calls = () => seen.slice();

Build once with spago build and once with iris build into separate output trees, then invoke each generated Main.main() in Node. Purs yields the first no-argument call [], then an argument containing block: "end" and inline: "nearest". Iris yields [] for both calls. The behavior field is currently omitted even by the purs path; this report isolates loss of the entire options argument.

The package FFI checks scrollIntoViewOptions.value0 (lines 17–27), which exists in purs output but not Iris’s { tag: "Just", _1: options }. A package-side conversion to JS primitives or FFI accessors, as suggested upstream, would remove reliance on compiler-specific constructor layout. Please treat this as a compatibility-policy/package fix discussion, not a request to change Iris’s constructor representation solely for this package. This report includes no private test-repository links or materials.

Dominant language
Rust
Stars
117
Forks
11
Avg merge
4h 22m
Merged PRs (30d)
126

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