Represent %todo with a Pexp_todo parsetree node by cknitt · Pull Request #9161 · rescript-lang/rescript

cknitt · 2026-11-01T09:23:51Z

Why

%todo is a language feature selected by an extension name, one of the items #8624 lists before the parsetree can be stamped as v1.

What changes

%todo and %todo("message") parse to a new node:

| Pexp_todo of {name_loc: Location.t; message: expression option}

The parser builds it when the payload is empty, a string literal, or a template without interpolations, with no attributes (Ast_todo.of_payload). Any other payload, such as %todo(1) or %todo({"braced"}), stays a Pexp_extension "todo" and is lowered as before.
The message stays an expression, so the printer keeps its spelling (quotes or backquotes, escapes) and the comments inside the payload.
The built-in PPX lowers the node with the same code as the extension, now Ast_exp_extension.todo. The generated JS and warning 110 are unchanged.
PPXs still see the extension: ast_mapper_to0 writes the node as %todo(...), and ast_mapper_from0 turns a %todo extension with a fitting payload back into the node, the same way the parser does.
The printers, comment table, parenthesization, iterator, mapper, depend, printast and editor completion handle the node like Pexp_raw.

Tests

tests/syntax_tests/data/ast-mapping/TodoExpressions.res: the v0 round trip.
tests/syntax_tests/data/printer/expr/todo.res: printing, comments around and inside the payload, and parentheses in pipes, field access and unary minus.
tests/syntax_tests/data/parsing/grammar/expressions/todo.res.
todo_roundtrips_through_ast0 in ounit_ast_mapper0_tests.ml: which payloads become a node (none, a string, a template, but not 1), the v0 wire shape, the exact tree (locations included) after a round trip, and a PPX-built %todo("x") arriving as the node.

Stacked on #9160.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Kbf3gJFAva9685fjvkajub

github-actions · 2026-11-01T09:24:15Z

Changelog

🏠 Internal

Represent %todo with a Pexp_todo parsetree node. PPXs still see the extension.

Semantic Diff

1 commit · Full page

Represent %todo with a Pexp_todo parsetree node

_{3c96010 · cknitt + Claude · Nov 01, 2026, 08:23 UTC}

Why

%todo is a language feature selected by an extension name, one of the items #8624 lists before the parsetree can be stamped as v1. The node holds the message as written; PPXs still see the extension.

AST modified (%todo)

let f = () => %todo("later")

parse

 expression
-  Pexp_extension "todo"
-    structure_item
-      Pstr_eval
-      expression
-        Pexp_constant PConst_string (source="later", semantic="later")
+  Pexp_todo
+  Some
+    expression
+      Pexp_constant PConst_string (source="later", semantic="later")

Review

Which payloads become a node? None, a string literal, or a template without interpolations, without attributes. Any other payload, such as %todo(1), stays an extension and is lowered as before, ignoring it.
Why an expression for the message rather than a string? It keeps the spelling (quotes or backquotes, escapes) and the comments inside the payload for the printer, as the extension did.

codecov · 2026-11-01T09:31:15Z

Codecov Report

❌ Patch coverage is 80.24691% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.67%. Comparing base (0c2890f) to head (3c96010).

Files with missing lines	Patch %	Lines
tests/ounit_tests/ounit_ast_mapper0_tests.ml	81.81%	4 Missing ⚠️
compiler/ml/typecore.ml	0.00%	3 Missing ⚠️
compiler/syntax/src/res_parens.ml	0.00%	3 Missing ⚠️
compiler/ml/printast.ml	0.00%	2 Missing ⚠️
analysis/src/completion_front_end.ml	0.00%	1 Missing ⚠️
analysis/src/utils.ml	0.00%	1 Missing ⚠️
compiler/frontend/ast_exp_extension.ml	90.90%	1 Missing ⚠️
compiler/ml/depend.ml	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                   Coverage Diff                   @@
##           todo-stdlib-jserror    #9161      +/-   ##
=======================================================
- Coverage                81.67%   81.67%   -0.01%     
=======================================================
  Files                      455      456       +1     
  Lines                    64859    64922      +63     
=======================================================
+ Hits                     52974    53024      +50     
- Misses                   11885    11898      +13

Files with missing lines	Coverage Δ
compiler/frontend/bs_builtin_ppx.ml	`90.39% <100.00%> (+0.06%)`	⬆️
compiler/ml/ast_helper.ml	`87.97% <100.00%> (+0.03%)`	⬆️
compiler/ml/ast_iterator.ml	`94.61% <100.00%> (+0.03%)`	⬆️
compiler/ml/ast_mapper.ml	`98.48% <100.00%> (+0.01%)`	⬆️
compiler/ml/ast_mapper_from0.ml	`79.46% <100.00%> (+0.09%)`	⬆️
compiler/ml/ast_mapper_to0.ml	`80.07% <100.00%> (+0.07%)`	⬆️
compiler/ml/ast_todo.ml	`100.00% <100.00%> (ø)`
compiler/ml/pprintast.ml	`91.72% <100.00%> (+0.01%)`	⬆️
compiler/syntax/src/res_comments_table.ml	`91.24% <100.00%> (+0.01%)`	⬆️
compiler/syntax/src/res_core.ml	`92.04% <100.00%> (+<0.01%)`	⬆️
... and 9 more

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

pkg-pr-new · 2026-11-01T09:37:26Z

Open in StackBlitz

rescript

npm i https://pkg.pr.new/rescript@9161

@rescript/belt

npm i https://pkg.pr.new/@rescript/belt@9161

@rescript/darwin-arm64

npm i https://pkg.pr.new/@rescript/darwin-arm64@9161

@rescript/linux-arm64

npm i https://pkg.pr.new/@rescript/linux-arm64@9161

@rescript/linux-x64

npm i https://pkg.pr.new/@rescript/linux-x64@9161

@rescript/runtime

npm i https://pkg.pr.new/@rescript/runtime@9161

@rescript/win32-x64

npm i https://pkg.pr.new/@rescript/win32-x64@9161

commit: 3c96010

cknitt · 2026-11-01T16:02:00Z

@codex review

chatgpt-codex-connector · 2026-11-01T16:02:16Z

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-01T16:03:25.549313Z	`afd0792`	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

Open a pull request for review
Mark a draft as ready
Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

chatgpt-codex-connector · 2026-11-01T16:03:24Z

Codex Review: Didn't find any major issues. More of your lovely PRs please.

Reviewed commit: afd0792a1c

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

Open a pull request for review
Mark a draft as ready
Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

Why: %todo is a language feature selected by an extension name, one of the items #8624 lists before the parsetree can be stamped as v1. The node holds the message as written; PPXs still see the extension. AST modified (%todo): Example: let f = () => %todo("later") Before (parse): expression Pexp_extension "todo" [ structure_item Pstr_eval expression Pexp_constant PConst_string (source="later", semantic="later") ] After (parse): expression Pexp_todo Some expression Pexp_constant PConst_string (source="later", semantic="later") Review: Which payloads become a node? None, a string literal, or a template without interpolations, without attributes. Any other payload, such as `%todo(1)`, stays an extension and is lowered as before, ignoring it. Review: Why an expression for the message rather than a string? It keeps the spelling (quotes or backquotes, escapes) and the comments inside the payload for the printer, as the extension did. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Kbf3gJFAva9685fjvkajub Signed-off-by: Christoph Knittel <ck@cca.io>

cknitt added this pull request to stack #9162 November 1, 2026 09:24

cknitt mentioned this pull request Nov 1, 2026

v0 AST round trip shortens the location of templates without interpolations #9164

Closed

cknitt mentioned this pull request Nov 1, 2026

Keep the location of templates without interpolations through the v0 AST #9165

Merged

cknitt force-pushed the todo-node branch from 2e476ea to 4e1b663 Compare November 1, 2026 11:23

cknitt mentioned this pull request Nov 1, 2026

Give template segments the location of their text, and keep template locations through the v0 AST #9166

Merged

cknitt force-pushed the todo-node branch from 4e1b663 to afd0792 Compare November 1, 2026 14:08

cknitt force-pushed the todo-node branch from afd0792 to 3c96010 Compare November 1, 2026 16:11

cknitt marked this pull request as ready for review November 1, 2026 16:24

cknitt requested a review from cristianoc November 1, 2026 16:24

cristianoc approved these changes Nov 1, 2026

View reviewed changes

cknitt merged commit cc827cd into master Nov 1, 2026
26 checks passed

cknitt deleted the todo-node branch November 1, 2026 19:42

cknitt mentioned this pull request Nov 2, 2026

Stamp parsetree v1: what remains before the AST can be frozen for PPXs #8624

Open

20 of 38 tasks

Navigation Menu

Repository navigation

Represent %todo with a Pexp_todo parsetree node - #9161

Represent %todo with a Pexp_todo parsetree node#9161
cknitt merged 1 commit into
todo-stdlib-jserrorfrom
todo-node

cknitt commented Nov 1, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Nov 1, 2026 •

edited

Loading

Uh oh!

codecov Bot commented Nov 1, 2026 •

edited

Loading

Uh oh!

pkg-pr-new Bot commented Nov 1, 2026 •

edited

Loading

Uh oh!

cknitt commented Nov 1, 2026

Uh oh!

chatgpt-codex-connector Bot commented Nov 1, 2026 •

edited

Loading

Uh oh!

chatgpt-codex-connector Bot commented Nov 1, 2026

Uh oh!

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

cknitt commented Nov 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Why

What changes

Tests

Uh oh!

github-actions Bot commented Nov 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Changelog

🏠 Internal

Semantic Diff

Uh oh!

codecov Bot commented Nov 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codecov Report

Uh oh!

pkg-pr-new Bot commented Nov 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

cknitt commented Nov 1, 2026

Uh oh!

chatgpt-codex-connector Bot commented Nov 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Codex Review Summary

Uh oh!

chatgpt-codex-connector Bot commented Nov 1, 2026

Uh oh!

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

cknitt commented Nov 1, 2026 •

edited

Loading

github-actions Bot commented Nov 1, 2026 •

edited

Loading

codecov Bot commented Nov 1, 2026 •

edited

Loading

pkg-pr-new Bot commented Nov 1, 2026 •

edited

Loading

chatgpt-codex-connector Bot commented Nov 1, 2026 •

edited

Loading