Hoist statement at-rules to the front of the aggregated stylesheet

[davesnx]

Browsers honor @import, @namespace and statement-form @layer a, b; only when they precede every other rule, and styled-ppx.generate preserved module order, so a statement emitted by a module ordered late landed mid-stylesheet where browsers ignore it (#581). After dedup, run now partitions the rendered rules into statement at-rules and everything else and writes the statements first, in their existing relative order. A rule is a statement at-rule when it starts with @ and contains no {; Render keeps block rules on one line too, so the brace is what tells @media (...) { ... } apart. Under --layers the statements come before the @property/@keyframes registrations, the aggregator's own @layer <libraries>; statement, and every wrapped block. Dedup is unchanged.

@charset is dropped with a warning naming the input file instead of hoisted: the generated file always opens with a comment, so @charset can never be its first bytes, and the output is UTF-8 regardless of what a module declares. documents/css-extraction.md records both decisions.

$ styled-ppx.generate a_styles.ml z_statements.ml      # z_ orders after a_
styled-ppx: z_statements.ml: dropping @charset: ...
/* This file is generated by styled-ppx, do not edit manually */
@import url("reset.css");
@namespace svg url("http://www.w3.org/2000/svg");
@layer utilities, base;
.a{color:red;}

Evidence at 091beef:

• New cram test packages/generate/test/statement-at-rules.t: two modules with no dependency edge, the statement module ordered second; covers the flat output and --layers. Red before the change: .a{color:red;} came first, @charset leaked through without a warning.
• packages/ppx/test/css-support/at-rule-statement-forms.t: expectation updated for the @charset drop and its warning; no reordering in that single-module case.
• make format-check, make build, make test: all exit 0.

Risk: two-way door. Output changes only for stylesheets that contain statement at-rules or @charset; a revert restores module order for them.

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1 Skipped Deployment

Project	Deployment	Actions	Updated
styled-ppx	Ignored	Preview	Sep 23, 2026 6:40am UTC