Keep @directive on @this functions by cknitt · Pull Request #9262 · rescript-lang/rescript

cknitt · 2026-11-07T15:28:16Z

@this functions dropped their @directive. There were two causes:

bs_builtin_ppx left the attribute on the unsafe_to_method call instead of the function, which is where translcore reads it. The PPX now moves @directive onto the inner function.
Pjs_fn_method ignored directive, and E.method_ had no parameter for it. lam_compile now passes it through.

A directive has to be the first statement of the body, so Js_dump prints it before let self = this. This also works for async functions and when self is unused.

New test: tests/tests/src/this_directive.res, a JS snapshot covering the plain, async and unused-self cases.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kbf3gJuq6rWZULJVY3ATmY

@this

Why: The @this rewrite left @directive on the unsafe_to_method call instead of the function, and the Pjs_fn_method path built the JS function without a directive, so it was dropped without a report. The PPX now moves @directive onto the inner function, E.method_ takes it, and the printer puts it before `let self = this`, since a directive must be the first statement of the body. JS modified (@this function with a directive): Example: let plain = @this @directive("'use cache'") (self, x) => self + x Before (js): function plain(x) { let self = this ; return self + x | 0; } After (js): function plain(x) { 'use cache'; let self = this ; return self + x | 0; } Fixes #9197 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Kbf3gJuq6rWZULJVY3ATmY Signed-off-by: Christoph Knittel <ck@cca.io>

github-actions · 2026-11-07T15:28:38Z

Changelog

🐛 Bug fix

Keep @directive on @this functions.

Semantic Diff

2 commits · Full page

Keep @directive on @this functions

_{66d6998 · cknitt + Claude · Nov 07, 2026, 15:28 UTC}

Why

The @this rewrite left @directive on the unsafe_to_method call instead of the function, and the Pjs_fn_method path built the JS function without a directive, so it was dropped without a report. The PPX now moves @directive onto the inner function, E.method_ takes it, and the printer puts it before let self = this, since a directive must be the first statement of the body.

JS modified (@this function with a directive)

let plain = @this @directive("'use cache'") (self, x) => self + x

js

 function plain(x) {
+  'use cache';
   let self = this ;
   return self + x | 0;
 }

Fixes #9197

✨ Print the this binding of a method without a space before the semicolon

_{ac091ee · cknitt + Claude · Nov 07, 2026, 15:41 UTC · new}

The space was left over from when the printer spelled out let self = by hand; no other statement puts a space before its semicolon.

JS modified (@this function)

let even = @this (o, x) => x + o

js

-let o = this ;
+let o = this;

codecov · 2026-11-07T15:33:19Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.74%. Comparing base (827be16) to head (ac091ee).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9262   +/-   ##
=======================================
  Coverage   81.74%   81.74%           
=======================================
  Files         457      457           
  Lines       65713    65717    +4     
=======================================
+ Hits        53715    53719    +4     
  Misses      11998    11998

Files with missing lines	Coverage Δ
compiler/core/js_dump.ml	`93.94% <100.00%> (+0.01%)`	⬆️
compiler/core/js_exp_make.ml	`66.28% <ø> (ø)`
compiler/core/lam_compile.ml	`89.92% <100.00%> (ø)`
compiler/frontend/ast_uncurry_gen.ml	`95.23% <100.00%> (ø)`
compiler/frontend/bs_builtin_ppx.ml	`90.67% <100.00%> (+0.06%)`	⬆️

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pkg-pr-new · 2026-11-07T15:39:20Z

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commit: ac091ee

@this

The space was left over from when the printer spelled out `let self =` by hand; no other statement puts a space before its semicolon. JS modified (@this function): Example: let even = @this (o, x) => x + o Before (js): let o = this ; After (js): let o = this; Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Kbf3gJuq6rWZULJVY3ATmY Signed-off-by: Christoph Knittel <ck@cca.io>

cknitt · 2026-11-07T15:43:14Z

@codex review

chatgpt-codex-connector · 2026-11-07T15:43:30Z

Codex Review Summary: ✅ Completed

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-07T15:58:30.782163Z	`ac091ee`	Manual request

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Reviewed commit: ac091eec07

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github-actions · 2026-11-07T15:56:00Z

Developer playground preview: https://rescript-lang.github.io/rescript/dev-playground/?version=pr-9262

cknitt · 2026-11-07T15:56:52Z

@codex review

chatgpt-codex-connector · 2026-11-07T15:58:29Z

Codex Review: Didn't find any major issues. Keep it up!

Reviewed commit: ac091eec07

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Comment thread compiler/core/lam_compile.ml Resolved

cknitt marked this pull request as ready for review November 7, 2026 16:01

cknitt requested a review from cristianoc November 7, 2026 16:01

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Keep @directive on @this functions - #9262

Keep @directive on @this functions#9262
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