fix(theme-check-node): normalise LiquidDoc paths on Windows

.changeset/tidy-snakes-listen.md

@@ -0,0 +1,5 @@
+---
+'@shopify/theme-check-node': patch
+---
+
+Fix cross-file LiquidDoc checks on Windows by normalising snippet paths before lookup.

packages/theme-check-node/src/index.spec.ts

@@ -1,7 +1,8 @@
-import { afterEach, assert, beforeEach, describe, expect, it } from 'vitest';
-import { Config, SourceCodeType, getTheme, getThemeFilesPathPattern } from './index';
+import { afterEach, assert, beforeEach, describe, expect, it, vi } from 'vitest';
+import path from 'node:path';
+import { Config, SourceCodeType, getTheme, getThemeFilesPathPattern, themeCheckRun } from './index';
 import { Workspace, makeTempWorkspace } from './test/test-helpers';
-import { pathToFileURL } from 'node:url';
+import { fileURLToPath, pathToFileURL } from 'node:url';
 
 describe('Unit: getTheme', () => {
   let workspace: Workspace;
@@ -49,3 +50,42 @@ describe('Unit: getThemeFilesPathPattern', () => {
     expect(normalizedGlob).to.equal(__dirname.replace(/\\/g, '/') + '/**/*.{liquid,json}');
   });
 });
+
+describe('Integration: themeCheckRun', () => {
+  it('reports LiquidDoc errors across files when paths use Windows separators', async () => {
+    const workspace = await makeTempWorkspace({
+      locales: {
+        'en.default.json': '{}',
+      },
+      sections: {
+        'main.liquid': "{% render 'card' %}",
+      },
+      snippets: {
+        'card.liquid': `
+          {% doc %}
+            @param {string} title - The card title
+          {% enddoc %}
+        `,
+      },
+    });
+    const originalRelative = path.relative;
+
+    const relativeSpy = vi.spyOn(path, 'relative').mockImplementation((from, to) => {
+      const relative = originalRelative(from, to);
+      if (typeof from === 'string' && from.startsWith('file:')) {
+        return relative.replace(/\//g, '\\');
+      }
+      return relative;
+    });
+
+    try {
+      const { offenses } = await themeCheckRun(fileURLToPath(workspace.rootUri));
+      expect(
+        offenses.filter(({ check }) => check === 'MissingRenderSnippetArguments'),
+      ).toHaveLength(1);
+    } finally {
+      relativeSpy.mockRestore();
+      await workspace.clean();
+    }
+  });
+});

packages/theme-check-node/src/index.ts

@@ -125,7 +125,7 @@ export async function themeCheckRun(
   ]));
   const docDefinitions = new Map(
     theme.map((file) => [
-      path.relative(URI.file(root).toString(), file.uri),
+      pathUtils.relative(file.uri, URI.file(root).toString()),
       memo(async (): Promise<DocDefinition | undefined> => {
         const ast = file.ast;
         if (!isLiquidHtmlNode(ast)) {