Fix templateExportDefault: true not adding export default to bare module-level templates

[Copilot]

Bare <template> tags in .gjs files (or .gts files without a TypeScript type annotation) were not getting export default prepended when templateExportDefault: true, leaving the file unchanged.

Root Cause

The preprocessing converts a bare <template> at module level into a BlockStatement directly inside Program. The existing export default injection logic lives in print() and only fires for nodes matched by isGlimmerTemplateParent — which covers ExportDefaultDeclaration and TypeScript ExpressionStatement > TSAsExpression > template, but not a BlockStatement that is a direct child of Program. Because embed() handles these template nodes before print() ever sees them, the injection was silently skipped.

Fix

Added the export default injection into embed(), where bare module-level templates are actually handled:

// src/printers.ts
const printed = printTemplateTag(content);

if (options.templateExportDefault && path.parent?.type === 'Program') {
  printed.unshift('export ', 'default ');
}

The path.parent?.type === 'Program' guard ensures only truly bare module-level templates are affected — templates nested inside ExportDefaultDeclaration, VariableDeclarator, class bodies, etc. are untouched.

Snapshot Updates

Four snapshots corrected in the templateExportDefault: true config suite:

File	Before	After
gjs/simple.gjs	<template>what</template>	export default <template>what</template>
gjs/simple-with-tag.gjs	bare top-level template unchanged	bare template gets export default; const-assigned templates unaffected
gjs/preceded-by-object.gjs	bare template unchanged	bare template gets export default
gts/issue-191-b.gts	<template>💩</template>	export default <template>💩</template>

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Bug] templateExportDefault: true does not add export default correctly</issue_title>
<issue_description>When templateExportDefault: true, I would expect this gjs file:

<template>Hello world</template>

to be transformed to

export default <template>Hello world</template>

However, this does not happen. The file remains unchanged.

This issue is also shown in the snapshot tests in this repo:

prettier-plugin-ember-template-tag/tests/unit-tests/config/__snapshots__/template-export-default.test.ts.snap

Lines 278 to 281 in 0ceae89

	exports[`config > templateExportDefault: true > it formats ../cases/gjs/simple.gjs 1`] = `
	"<template>what</template>
	"
	`;

^^ this assertion should be export default <template>what</template>

🌍 Environment

• prettier-plugin-ember-template-tag version: 2.1.0
  </issue_description>

<agent_instructions>Do we have any tests for this behavior? If not, create a failing test for it.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes [Bug] templateExportDefault: true does not add export default correctly #402

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[evoactivity]

This looks ok, @gitKrystan any reason to keep this a draft or can we merge to get it in next release?