# Firebase Functions V1 vs V2 Signature Mapping

This reference maps legacy V1 functions to their modern V2 equivalents. When
using the compatibility shim, you can destructure the V2 event object using the
exact parameter names from the legacy V1 trigger signature (`change`,
`snapshot`, `message`, `object`) alongside `context`.

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## Cloud Firestore

| V1 Trigger                        | V2 Equivalent         | Destructuring Pattern     |
| :-------------------------------- | :-------------------- | :------------------------ |
| `firestore.document().onWrite()`  | `onDocumentWritten()` | `({ change, context })`   |
| `firestore.document().onCreate()` | `onDocumentCreated()` | `({ snapshot, context })` |
| `firestore.document().onUpdate()` | `onDocumentUpdated()` | `({ change, context })`   |
| `firestore.document().onDelete()` | `onDocumentDeleted()` | `({ snapshot, context })` |

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## Cloud Pub/Sub

| V1 Trigger                   | V2 Equivalent          | Destructuring Pattern    |
| :--------------------------- | :--------------------- | :----------------------- |
| `pubsub.topic().onPublish()` | `onMessagePublished()` | `({ message, context })` |
| `pubsub.schedule().onRun()`  | `onSchedule()`         | Access `event` directly  |

> [!NOTE] Scheduled functions moved from the `pubsub` namespace to the
> `scheduler` namespace in V2.

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## Realtime Database

| V1 Trigger                  | V2 Equivalent      | Destructuring Pattern     |
| :-------------------------- | :----------------- | :------------------------ |
| `database.ref().onWrite()`  | `onValueWritten()` | `({ change, context })`   |
| `database.ref().onCreate()` | `onValueCreated()` | `({ snapshot, context })` |
| `database.ref().onUpdate()` | `onValueUpdated()` | `({ change, context })`   |
| `database.ref().onDelete()` | `onValueDeleted()` | `({ snapshot, context })` |

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## Cloud Storage

| V1 Trigger                            | V2 Equivalent               | Destructuring Pattern   |
| :------------------------------------ | :-------------------------- | :---------------------- |
| `storage.object().onArchive()`        | `onObjectArchived()`        | `({ object, context })` |
| `storage.object().onDelete()`         | `onObjectDeleted()`         | `({ object, context })` |
| `storage.object().onFinalize()`       | `onObjectFinalized()`       | `({ object, context })` |
| `storage.object().onMetadataUpdate()` | `onObjectMetadataUpdated()` | `({ object, context })` |

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## HTTP / Callables

| V1 Trigger          | V2 Equivalent       | Destructuring Pattern          |
| :------------------ | :------------------ | :----------------------------- |
| `https.onRequest()` | `https.onRequest()` | Standard Express `(req, res)`  |
| `https.onCall()`    | `https.onCall()`    | Destructure `({ data, auth })` |

> [!IMPORTANT] **HTTP Callables do NOT use the Destructuring Shim.** In V2, the
> handler receives a single `CallableRequest` object (not a `CloudEvent`). You
> should destructure properties like `data`, `auth`, and `app` directly from it.
> The traditional `context` object is **unavailable**.

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## Auth (Blocking)

| V1 Trigger                   | V2 Equivalent                   | Destructuring Pattern   |
| :--------------------------- | :------------------------------ | :---------------------- |
| `auth.user().beforeSignIn()` | `identity.beforeUserSignedIn()` | Access `event` directly |
| `auth.user().beforeCreate()` | `identity.beforeUserCreated()`  | Access `event` directly |

> [!NOTE] Auth Blocking triggers moved to the `identity` namespace in V2.

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## Cloud Tasks

| V1 Trigger                       | V2 Equivalent        | Destructuring Pattern   |
| :------------------------------- | :------------------- | :---------------------- |
| `tasks.taskQueue().onDispatch()` | `onTaskDispatched()` | Access `event` directly |