Publishing to crates.io | Fern Documentation

Publish your public-facing Fern Rust SDK to the crates.io registry. After following the steps on this page, you’ll have a versioned crate published on crates.io.

Versioned package published on crates.io

This page assumes that you have:

An initialized fern folder. See Set up the fern folder.
A GitHub repository for your SDK. See Project Structure.

Configure `generators.yml`

Configure `output` location

Change the output location in generators.yml from local-file-system (the default) to crates to indicate that Fern should publish your crate directly to the crates.io registry:

generators.yml

1 groups: 
2   rust-sdk:
3     generators:
4       - name: fernapi/fern-rust-sdk
5         version: 0.13.3
6         output:
7           location: crates

Add a unique crate name

Your crate name must be unique in the crates.io registry, otherwise publishing your SDK will fail. Update your crate name if you haven’t done so already:

generators.yml

1 groups: 
2   rust-sdk:
3     generators:
4       - name: fernapi/fern-rust-sdk
5         version: 0.13.3
6         output:
7           location: crates
8           package-name: your-crate-name

Configure `clientClassName`

The clientClassName option controls the name of the generated client struct. This is the name users will use when instantiating your SDK client.

generators.yml

1 groups: 
2   rust-sdk:
3     generators:
4       - name: fernapi/fern-rust-sdk
5         version: 0.13.3
6         output:
7           location: crates
8           package-name: your-crate-name
9         config:
10           clientClassName: YourClientName # must be PascalCase

Add repository location

Add the path to your GitHub repository to generators.yml:

generators.yml

1 groups: 
2   rust-sdk:
3     generators:
4       - name: fernapi/fern-rust-sdk
5         version: 0.13.3
6         output:
7           location: crates
8           package-name: your-crate-name
9         config:
10           clientClassName: YourClientName
11         github: 
12           repository: your-org/your-rust-sdk

Set up crates.io publishing authentication

Log into crates.io

Log into crates.io using your GitHub account.

Navigate to Account settings

Click on your profile picture in the top right corner.
Select Account Settings.
Go to the API Tokens section.

Create a new API token

Click New Token.
Name your token (e.g., “Fern SDK Publishing”).
Under Scopes, select publish-new to publish new crates and publish-update to update existing crates.
Click Generate Token.

Save your new token immediately. It won’t be displayed again after you leave the page.

Configure crates.io authentication token

Add token: ${CRATES_IO_API_KEY} to generators.yml to tell Fern to use the CRATES_IO_API_KEY environment variable for authentication when publishing to crates.io.

generators.yml

1 groups: 
2   rust-sdk:
3     generators:
4       - name: fernapi/fern-rust-sdk
5         version: 0.13.3
6         output:
7           location: crates
8           package-name: your-crate-name
9           token: ${CRATES_IO_API_KEY}
10         config:
11           clientClassName: YourClientName
12         github: 
13           repository: your-org/your-rust-sdk

Publish your SDK

Decide how you want to publish your SDK to crates.io. You can use GitHub workflows for automated releases or publish directly via the CLI.

Release via a GitHub workflow (recommended)

Set up a release workflow via GitHub Actions so you can trigger new SDK releases directly from your source repository.

Set up authentication

Open your source repository in GitHub. Click on the Settings tab in your repository. Then, under the Security section, open Secrets and variables > Actions.

You can also use the url https://github.com/<your-repo>/settings/secrets/actions.

Add secret for your crates.io token

Select New repository secret.
Name your secret CRATES_IO_API_KEY.
Add the corresponding token you generated above.
Click Add secret.

Add secret for your Fern token

Select New repository secret.
Name your secret FERN_TOKEN.
Add your Fern token. If you don’t already have one, generate one by running fern token. By default, the fern_token is generated for the organization listed in fern.config.json.
Click Add secret.

Set up a new workflow

Set up a CI workflow that you can manually trigger from the GitHub UI. In your repository, navigate to Actions. Select New workflow, then Set up workflow yourself. Add a workflow that’s similar to this:

.github/workflows/publish.yml

1 name: Publish Rust SDK
2 
3 on:
4 workflow_dispatch:
5   inputs:
6     version:
7       description: "The version of the Rust SDK that you would like to release"
8       required: true
9       type: string
10 
11 jobs:
12 release:
13   runs-on: ubuntu-latest
14   steps:
15     - name: Checkout repo
16       uses: actions/checkout@v4
17 
18     - name: Install Fern CLI
19       run: npm install -g fern-api
20 
21     - name: Release Rust SDK
22       env:
23         FERN_TOKEN: ${{ secrets.FERN_TOKEN }}
24         CRATES_IO_API_KEY: ${{ secrets.CRATES_IO_API_KEY }}
25       run: |
26         fern generate --group rust-sdk --version ${{ inputs.version }} --log-level debug

Regenerate and release your SDK

Navigate to the Actions tab, select the workflow you just created, specify a version number, and click Run workflow. This regenerates your SDK.

The rest of the release process depends on your chosen mode:

Release mode (default): If you didn’t specify a mode or set mode: release, no further action is required. Fern automatically tags the new release with your specified version number and initiates the publishing workflow in your SDK repository.
Pull request or push mode: If you set mode: pull-request or mode: push, Fern creates a pull request or pushes to a branch respectively. Review and merge the PR (pull-request) or branch (push), then tag a new release to initiate the publishing workflow in your SDK repository.

Once the workflow completes, you can view your new release by logging into crates.io, navigating to Dashboard, and looking under My Crates.

Release via CLI and environment variables

Set crates.io environment variable

Set the CRATES_IO_API_KEY environment variable on your local machine:

$ export CRATES_IO_API_KEY=your-actual-rust-token

Regenerate and release your SDK

Regenerate your SDK, specifying the version:

$ fern generate --group rust-sdk --version <version>

The rest of the release process depends on your chosen mode:

Release mode (default): If you didn’t specify a mode or set mode: release, no further action is required. Fern automatically tags the new release with your specified version number and initiates the publishing workflow in your SDK repository.
Pull request or push mode: If you set mode: pull-request or mode: push, Fern creates a pull request or pushes to a branch respectively. Review and merge the PR (pull-request) or branch (push), then tag a new release to initiate the publishing workflow in your SDK repository.

Once the workflow completes, you can view your new release by logging into crates.io, navigating to Dashboard, and looking under My Crates.

Configure generators.yml

Configure output location

Add a unique crate name

Configure clientClassName

Add repository location

Set up crates.io publishing authentication

Log into crates.io

Navigate to Account settings

Create a new API token

Configure crates.io authentication token

Publish your SDK

Release via a GitHub workflow (recommended)

Set up authentication

Add secret for your crates.io token

Add secret for your Fern token

Set up a new workflow

Regenerate and release your SDK

Release via CLI and environment variables

Set crates.io environment variable

Regenerate and release your SDK

Configure `generators.yml`

Configure `output` location

Configure `clientClassName`