Fix UnusedAssign false positive inside inline {% liquid ... style ... endstyle %}

[rushikeshmore]

What are you adding in this PR?

Fixes a false-positive UnusedAssign warning for variables that are only referenced inside a style block within an inline {% liquid %} tag.

Repro from the issue:

{%- liquid
  assign shopName = shop.name
  capture example
    echo 'Shopify'
  endcapture

  style
    echo example
    echo shopName
  endstyle
-%}

Before the fix, both example and shopName get reported as "assigned but not used". After the fix, no offense is reported.

Root cause

The CST mapping in packages/liquid-html-parser/src/stage-1-cst.ts has two liquidRawTagImpl entries — one for the main Liquid grammar (top-level {% style %}...{% endstyle %}) and one for the LiquidStatement grammar (inline {% liquid ... style ... endstyle %}).

The top-level mapping already distinguishes:

• schema / raw → TextNodeGrammar (raw string, not visited)
• everything else (style, stylesheet, javascript) → re-parsed with grammars.Liquid so children end up in the AST

The inline mapping forced every raw tag body through TextNodeGrammar. That meant the echo example and echo shopName inside the inline style block never produced VariableLookup nodes, and UnusedAssign (which walks VariableLookup to decide "used") never registered them as used.

Fix

Mirror the top-level switch in the inline mapping. schema and raw still stay as raw text; every other raw tag is re-parsed with grammars.LiquidStatement (the inline-liquid grammar) so references inside style and friends become first-class AST nodes.

Adds a regression test in unused-assign/index.spec.ts using the exact snippet from #465.

Related

This supersedes the grammar-level attempt in #683 — the real bug was not in the grammar (style is a valid raw tag name in both the top-level and inline-liquid grammars) but in how the CST mapping re-parsed the raw body.

What's next? Any followup issues?

The inline form of {% liquid ... javascript %} / {% liquid ... stylesheet %} / {% liquid ... schema %} is exotic but now produces the same AST shape as their top-level counterparts. No follow-ups I can see.

Before you deploy

• I included a patch bump changeset for @shopify/liquid-html-parser
• Full vitest run green — 294 files, 1860 tests, 1 pre-existing skip
• yarn format:check clean
• yarn workspace ... type-check clean for @shopify/liquid-html-parser, @shopify/theme-check-common, @shopify/theme-check-node, @shopify/theme-language-server-common, @shopify/prettier-plugin-liquid

Closes #465

[rushikeshmore]

Friendly check-in — this PR has been open for two weeks. CLA + mergeability checks are green. Happy to rebase, split commits, or adjust anything that would make review easier.

[rushikeshmore]

@charlespwd @graygilmore — could one of you take a look when you have a moment? PR's been open three weeks, CLA + mergeability checks are green, and it's a small contained fix for #465 (UnusedAssign false positive in inline {% liquid ... style %}). Happy to rebase or split commits if helpful.

[aswamy]

@rushikeshmore Thank you for the submission. Unfortunately, changing the stage-1-cst also opens behavioural changes to StaticStylesheetAndJavascriptTags. Specifically, stylesheet and javascript will fire those theme-checks when inside of liquid tags. This puts them in a perpetual invalid state because if you're nested inside liquid tag, every line is resolved as liquid code, but the theme-check StaticStylesheetAndJavascriptTags prevents liquid code inside of stylesheet/javascript tag.

If you do re-attempt this problem, please follow the PR template for the description https://github.com/Shopify/theme-tools/blob/main/.github/PULL_REQUEST_TEMPLATE.md