[cknitt]

Stacked on #8905.

A line comment inside the operand of switch, try, if, while or a loop moved behind the opening brace when the formatter kept the operand on one line, and the next format attached it to the block, so the output changed on every run:

// input
let x = switch [
  a, // c
  b,
] { | _ => 1 }

// before, pass 1           // before, pass 2
let x = switch [a, b] { // c   let x = switch [a, b] {
| _ => 1                       // c
}                              | _ => 1
                               }

The comment is printed as a line suffix in a flat group. Operands followed by a block now force the groups around such a comment to break (Doc.break_before_line_suffixes). A comment trailing the whole operand, which no group break can move, goes into parentheses with the operand, as if conditions already did:

let x = switch [
  a, // c
  b,
] {
| _ => 1
}

let x = switch (
  a // c
) {
| _ => 1
}

Making every same-line line comment break its group would also fix this, but it reformats stable code such as foo(v :> b) // comment (3 snapshot changes), so the change is limited to operands before a block.

Checked with a harness of 10 operand positions × 8 operand/comment shapes: all 80 now format idempotently (48 did not before). A 330-case differential of other contexts formats as before apart from the comment-in-operand cases.

New test: printer/comments/operandBeforeBlock.res.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EUpL6dKCiSwAeriDGRHqNr

[codecov]

Codecov Report

❌ Patch coverage is 80.39216% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.20%. Comparing base (798978d) to head (cfa5e3e).

Files with missing lines	Patch %	Lines
compiler/syntax/src/res_printer.ml	81.81%	6 Missing ⚠️
compiler/syntax/src/res_doc.ml	77.77%	4 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##           parsetree-spread    #8906   +/-   ##
=================================================
  Coverage             81.20%   81.20%           
=================================================
  Files                   458      458           
  Lines                 63933    63957   +24     
=================================================
+ Hits                  51918    51938   +20     
- Misses                12015    12019    +4     

Files with missing lines	Coverage Δ
compiler/syntax/src/res_doc.ml	69.04% <77.77%> (+0.81%)	⬆️
compiler/syntax/src/res_printer.ml	94.26% <81.81%> (+0.01%)	⬆️

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commit: cfa5e3e

[cknitt]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

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

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-21T18:23:03.765759Z	cfa5e3e	Manual request

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• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: cc7571ef6f

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
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• 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".

[chatgpt-codex-connector]

Handle grouped suffixes without a later break

A Group does not guarantee that breaking it will encounter a LineBreak after its line suffix. For example, print_object_get_doc produces a group containing parent_doc; "[\"member\"]"; with an operand such as switch obj // c\n["member"] { ... }, the comment is attached to obj, but there is no break after that suffix inside the group. Returning false here prevents print_operand_before_brace from adding protective parentheses, and the inserted BreakParent only changes the mode—it does not flush the queued suffix—so the comment still prints after the following { and continues relocating on subsequent formats.

Useful? React with 👍 / 👎.

[github-actions]

Semantic diff: https://cdn.rescript-lang.org/semantic-diff/pr-8906/index.html?v=cfa5e3e86

[cknitt]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Can't wait for the next one!

Reviewed commit: cfa5e3e866

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".