npm package: @fluid-experimental/dds-interceptions
Description: Distributed Data Structures that support an interception callback
Author: Microsoft and contributors
Latest version: 2.92.0

# @fluid-experimental/dds-interceptions

This package provides factory methods to create a wrapper around some of the basic Distributed Data Structures (DDS) that support an interception callback. Apps can provide a callback when creating these wrappers and this callback will be called when the DDS is modified. This allows apps to support features such as basic user attribution on a SharedString.

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**IMPORTANT: This package is experimental.**
**Its APIs may change without notice.**

**Do not use in production scenarios.**

## Using Fluid Framework libraries

When taking a dependency on a Fluid Framework library's public APIs, we recommend using a `^` (caret) version range, such as `^1.3.4`.
While Fluid Framework libraries may use different ranges with interdependencies between other Fluid Framework libraries,
library consumers should always prefer `^`.

If using any of Fluid Framework's unstable APIs (for example, its `beta` APIs), we recommend using a more constrained version range, such as `~`.

## Installation

To get started, install the package by running the following command:

```bash
npm i @fluid-experimental/dds-interceptions
```

## API Documentation

API documentation for **@fluid-experimental/dds-interceptions** is available at <https://fluidframework.com/docs/apis/dds-interceptions>.

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## Shared String With Interception

It provides `createSharedStringWithInterception` that accepts a SharedString, the data store context and a callback, and returns a SharedString object:

```typescript
function createSharedStringWithInterception(
	sharedString: SharedString,
	context: IFluidDataStoreContext,
	propertyInterceptionCallback: (props?: MergeTree.PropertySet) => MergeTree.PropertySet,
): SharedString;
```

When a function is called that modifies the SharedString (for example, insertText), it calls propertyInterceptionCallback with the provided properties. The callback function can then provide the new set of properties that it wants to set. The operation in the called function and any operations in the callback are batched, i.e., they are guaranteed to be in order and will be applied together.

For example, to support a feature like simple user attribution, the app can append the user information to the properties in the callback. The user information can than be retrieved by getting the properties at any position.

## Shared Map With Interception

It provides `createSharedMapWithInterception` that accepts a SharedMap, the data store context and a callback, and returns a SharedMap object:

```typescript
function createSharedMapWithInterception(
	sharedMap: SharedMap,
	context: IFluidDataStoreContext,
	setInterceptionCallback: (sharedMap: ISharedMap, key: string, value: any) => void,
): SharedMap;
```

When set is called on the SharedMap, it calls setInterceptionCallback with the underlying SharedMap, the key and value that the set was called with. The callback function can then perform operations on either the underlying SharedMap or any other DDS. The original set operation and any operations in the callback are batched, i.e., they are guaranteed to be in order and will be applied together.

Example: To support a feature like simple user attribution, in the callback, the app can set the user information in the underlying SharedMap against a key derived from the original key - say against "key.attribute". Or, it could use a separate SharedMap to store the user information against the same key.

## Shared Directory / Sub Directory With Interception

It provides `createdDirectoryWithInterception` that accepts an IDirectory object, the data store context and a callback, and returns an IDirectory object:

```typescript
function createDirectoryWithInterception<T extends IDirectory>(
	baseDirectory: T,
	context: IFluidDataStoreContext,
	setInterceptionCallback: (
		baseDirectory: IDirectory,
		subDirectory: IDirectory,
		key: string,
		value: any,
	) => void,
): T;
```

It can be used to wrap a SharedDirectory or one of it's subdirectories to get an interception callback when set is called on the object. The callback function is passed the following:

-   baseDirectory: This is the outermost directory in this directory structure that was wrapped. For example, when a SharedDirectory (say 'root') is wrapped, then a set on it or any of its sub directories will be passed 'root' as the baseDirectory.
-   subDirectory: This is the directory that the set is called on and which calls the callback.
-   key: They key that set was called with.
-   value: They value that set was called with.

The original set operation and any operations in the callback function are batched, i.e., they are guaranteed to in order and will be applied together.

Example: To support a feature like simple user attribution, in the callback, the app can set the user information in a sub directory of the original object against the same key.

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## Minimum Client Requirements

These are the platform requirements for the current version of Fluid Framework Client Packages.
These requirements err on the side of being too strict since within a major version they can be relaxed over time, but not made stricter.
For Long Term Support (LTS) versions this can require supporting these platforms for several years.

It is likely that other configurations will work, but they are not supported: if they stop working, we do not consider that a bug.
If you would benefit from support for something not listed here, file an issue and the product team will evaluate your request.
When making such a request please include if the configuration already works (and thus the request is just that it becomes officially supported), or if changes are required to get it working.

### Supported Runtimes

-   NodeJs ^20.10.0 except that we will drop support for it [when NodeJs 20 loses its upstream support on 2026-04-30](https://github.com/nodejs/release#release-schedule), and will support a newer LTS version of NodeJS (22) at least 1 year before 20 is end-of-life. This same policy applies to NodeJS 22 when it is end of life (2027-04-30).
    -   Running Fluid in a Node.js environment with the `--no-experimental-fetch` flag is not supported.
-   Modern browsers supporting the es2022 standard library: in response to asks we can add explicit support for using babel to polyfill to target specific standards or runtimes (meaning we can avoid/remove use of things that don't polyfill robustly, but otherwise target modern standards).

### Supported Tools

-   TypeScript 5.4:
    -   All [`strict`](https://www.typescriptlang.org/tsconfig) options are supported.
    -   [`strictNullChecks`](https://www.typescriptlang.org/tsconfig) is required.
    -   [Configuration options deprecated in 5.0](https://github.com/microsoft/TypeScript/issues/51909) are not supported.
    -   `exactOptionalPropertyTypes` is currently not fully supported.
        If used, narrowing members of Fluid Framework types types using `in`, `Reflect.has`, `Object.hasOwn` or `Object.prototype.hasOwnProperty` should be avoided as they may incorrectly exclude `undefined` from the possible values in some cases.
-   [webpack](https://webpack.js.org/) 5
    -   We are not intending to be prescriptive about what bundler to use.
        Other bundlers which can handle ES Modules should work, but webpack is the only one we actively test.

### Module Resolution

[`Node16`, `NodeNext`, or `Bundler`](https://www.typescriptlang.org/tsconfig#moduleResolution) resolution should be used with TypeScript compilerOptions to follow the [Node.js v12+ ESM Resolution and Loading algorithm](https://nodejs.github.io/nodejs.dev/en/api/v20/esm/#resolution-and-loading-algorithm).
Node10 resolution is not supported as it does not support Fluid Framework's API structuring pattern that is used to distinguish stable APIs from those that are in development.

### Module Formats

-   ES Modules:
    ES Modules are the preferred way to consume our client packages (including in NodeJs) and consuming our client packages from ES Modules is fully supported.
-   CommonJs:
    Consuming our client packages as CommonJs is supported only in NodeJS and only for the cases listed below.
    This is done to accommodate some workflows without good ES Module support.
    If you have a workflow you would like included in this list, file an issue.
    Once this list of workflows motivating CommonJS support is empty, we may drop support for CommonJS one year after notice of the change is posted here.

    -   Testing with Jest (which lacks [stable ESM support](https://jestjs.io/docs/ecmascript-modules) due to [unstable APIs in NodeJs](https://github.com/nodejs/node/issues/37648))

## Contribution Guidelines

There are many ways to [contribute](https://github.com/microsoft/FluidFramework/blob/main/CONTRIBUTING.md) to Fluid.

-   Participate in Q&A in our [GitHub Discussions](https://github.com/microsoft/FluidFramework/discussions).
-   [Submit bugs](https://github.com/microsoft/FluidFramework/issues) and help us verify fixes as they are checked in.
-   Review the [source code changes](https://github.com/microsoft/FluidFramework/pulls).
-   [Contribute bug fixes](https://github.com/microsoft/FluidFramework/blob/main/CONTRIBUTING.md).

Detailed instructions for working in the repo can be found in the [Wiki](https://github.com/microsoft/FluidFramework/wiki).

This project has adopted the [Microsoft Open Source Code of Conduct](https://opensource.microsoft.com/codeofconduct/).
For more information see the [Code of Conduct FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact [opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional questions or comments.

This project may contain Microsoft trademarks or logos for Microsoft projects, products, or services.
Use of these trademarks or logos must follow Microsoft’s [Trademark & Brand Guidelines](https://www.microsoft.com/trademarks).
Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship.

## Help

Not finding what you're looking for in this README? Check out [fluidframework.com](https://fluidframework.com/docs/).

Still not finding what you're looking for? Please [file an issue](https://github.com/microsoft/FluidFramework/wiki/Submitting-Bugs-and-Feature-Requests).

Thank you!

## Trademark

This project may contain Microsoft trademarks or logos for Microsoft projects, products, or services.

Use of these trademarks or logos must follow Microsoft's [Trademark & Brand Guidelines](https://www.microsoft.com/en-us/legal/intellectualproperty/trademarks/usage/general).

Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship.

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