Add v1 compat utilities for Pub/Sub event triggers

[taeold]

Update v2/pubsub/'s onMessagePublished to expose v1-compatible accessors, enabling usage like:

export const onMessage = onMessagePublished("topic", (event) => {
  const { context, message } = event;
  functions.logger.info(context.eventType, message.json);
});

Introduce decorateLegacyEvent helper so providers can attach v1-style getters (context + extras).

[gemini-code-assist]

Summary of Changes

Hello @taeold, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a compatibility layer for Google Cloud Pub/Sub event triggers, allowing v2 functions to expose event data in a format consistent with v1 Cloud Functions. This change facilitates smoother migration and interoperability by providing familiar context and message accessors directly on the event object, reducing the need for extensive code refactoring when upgrading from v1 to v2 event structures.

Highlights

• V1 Compatibility for Pub/Sub: The onMessagePublished function in v2/pubsub/ now provides v1-compatible accessors for event data.
• New decorateLegacyEvent Utility: A new helper function, decorateLegacyEvent, is introduced to attach v1-style context and other getters to v2 CloudEvents.
• Enhanced Event Structure: The MessagePublishedEvent interface is added, extending CloudEvent with context (v1-compatible EventContext) and message (v1-compatible LegacyMessage) properties for easier access.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request introduces compatibility utilities to provide v1-style event accessors for v2 Pub/Sub triggers. A new compat.ts file adds a generic decorateLegacyEvent helper to attach lazy-evaluated properties to events. This is then used in v2/providers/pubsub.ts to add context and message getters to onMessagePublished events, making them compatible with the v1 SDK's event structure. The changes are well-tested and look good. My review includes a couple of suggestions to improve type safety and code clarity in the new compatibility helpers.

[gemini-code-assist]

The outer type cast as Params is redundant because options.params is already of type Params | undefined and {} as Params provides the Params type in the nullish-coalescing case. You can simplify this line for better readability.

Suggested change

	params: (options.params ?? ({} as Params)) as Params,
	params: options.params ?? ({} as Params),