Fix undefined when no options or prefix were provided.

[RadValentin]

Fixes #135

prefixPlugin remains typed as PluginCreator<T> and safely returns a no-op plugin when options or prefix is missing.

[Copilot]

🟡 Changes recommended

It claims to fix #135, but the published TypeScript declaration still exposes PluginCreator<T> (keeping opts optional), so the issue’s required-signature requirement is not actually addressed.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR prevents postcss-prefix-selector from prefixing selectors with the literal string undefined when the plugin is invoked without options or without a prefix, and adds regression coverage for those cases (noting that the linked issue #135 is specifically about TypeScript’s published call signature).

Changes:

• Add a runtime guard in index.js to no-op when options is missing/invalid or options.prefix is not provided.
• Add tests asserting the plugin makes no changes when called with no options or with {}.
• Rename the coverage script from test-cov to test:cov.

File summaries

File	Description
index.js	Adds a no-op early return to avoid undefined prefixing when prefix is missing.
test/test.js	Adds regression tests for no-options / no-prefix invocations.
package.json	Renames the coverage test script to test:cov.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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