Add markdown guide for data connect internals

[tammam-g]

How do people feel about adding docs like these to provide quick context for contributing for llm agents (and people)?

[gemini-code-assist]

Summary of Changes

Hello @tammam-g, 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 foundational markdown document aimed at educating developers on the internal architecture and operational flows of the Firebase Data Connect feature within the firebase-tools CLI. Its primary goal is to enhance understanding and facilitate contributions to this specific part of the codebase.

Highlights

• New Documentation Added: I've added a new markdown document, docs/data-connect.md, to the repository. This document serves as a comprehensive internal guide for the Firebase Data Connect feature.
• Detailed Data Connect Internals: The new guide provides an in-depth look at Data Connect, covering its product overview, its place within the firebase-tools project structure, and its core components. It details how Data Connect interacts with the CLI's command framework, authentication system, and the Emulator Suite.
• Interaction Flows Explained: The document clarifies the interaction flows for Data Connect, specifically differentiating between local emulation scenarios (using pg-lite) and the deployment process, including schema migration and service deployment.
• Contribution Guide: The guide also includes practical steps and advice for developers looking to contribute to the Firebase CLI, with a particular focus on understanding and modifying the Data Connect feature.

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[gemini-code-assist]

Code Review

This pull request adds a new internal developer guide for Firebase Data Connect. The guide is well-structured and provides a good overview of the feature's architecture within firebase-tools. I've added a few suggestions to improve clarity and correct some minor inaccuracies in the documentation.

[gemini-code-assist]

The comma after 'Firebase Data Connect' is grammatically incorrect and slightly hinders readability.

Suggested change

	Firebase Data Connect, is a feature that enables developers to build GraphQL-based data APIs backed by existing SQL databases.
	Firebase Data Connect is a feature that enables developers to build GraphQL-based data APIs backed by existing SQL databases.

[gemini-code-assist]

The repository name appears to be duplicated here. For accuracy, it should be firebase-tools/.

Suggested change

	firebase-firebase-tools/
	firebase-tools/

[gemini-code-assist]

The project structure diagram is missing the dataconnectEmulator.ts file, which is a key component mentioned later in the document. The description for the dataconnect/ directory could be more precise.

Suggested change

	│ ├── dataconnect/ # Data Connect Emulator specific logic.
	│ │ └── pgliteServer.ts # Manages the in-memory pglite Postgres instance.
	│ ├── storage/ # Storage Emulator implementation.
	│ ├── controller.ts # Main controller to start, stop, and manage emulators.
	│ ├── downloadableEmulators.ts # Handles downloading of JAR-based emulators.
	│ ├── hub.ts # The central discovery service for all emulators.
	│ └── registry.ts # A static registry for running emulators to discover each other.
	│ ├── dataconnect/ # Core logic for Data Connect feature.
	│ │ ├── client.ts # Client for interacting with the Data Connect backend API.
	│ │ ├── load.ts # Logic for loading and parsing dataconnect.yaml and connector.yaml.
	│ │ ├── schemaMigration.ts # Handles SQL schema diffing and migration.
	│ │ └── build.ts # Logic for building schema and connectors from source.
	│ ├── emulator/
	│ ├── auth/ # Auth Emulator implementation.
	│ ├── dataconnect/ # Data Connect Emulator specific logic.
	│ │ └── pgliteServer.ts # Manages the in-memory pglite Postgres instance.
	│ │ └── dataconnectEmulator.ts # The Data Connect emulator.
	│ ├── storage/ # Storage Emulator implementation.
	│ ├── controller.ts # Main controller to start, stop, and manage emulators.
	│ ├── downloadableEmulators.ts # Handles downloading of JAR-based emulators.
	│ ├── hub.ts # The central discovery service for all emulators.
	│ └── registry.ts # A static registry for running emulators to discover each other.

[fredzqm]

Would expect those FDC code be there.

• src/deploy/dataconnect
• src/mcp/tools/dataconnect
• template/init/dataconnect
• src/init/dataconnect

[fredzqm]

How is this created? Generated by AI?

Those kind of docs if not co-located with code will get stable and obsolete very quickly.

[tammam-g]

How is this created? Generated by AI?

Those kind of docs if not co-located with code will get stable and obsolete very quickly.

Yeah created by AI, wanted to get quick idea on how people feel about adding this. It can become obsolete but I feel like it will still capture 90+% of how things work unless there is a large refactor, in which case updating this file should be part of the PR ideally. Trying to hit a nice medium between being too specific and too general.

For context: to generate this prompt I had to use around 850k token context which if I wanted to include all in gemini-cli it will run out of tokens quick.