Struct VertexCredentials 

pub struct VertexCredentials { /* private fields */ }

Available on crate feature vertex only.

Credential source for Vertex AI authentication.

Carries either a static bearer token (no async refresh) or an ADC-backed TokenProvider that fetches and caches tokens via gcp_auth.

Construct with VertexCredentials::from_token, VertexCredentials::from_adc, or VertexCredentials::from_env.

Implementations

impl VertexCredentials

pub fn from_token(token: impl Into<String>) -> Self

Use a pre-obtained OAuth2 bearer token directly.

The token is used verbatim; no refresh is performed. Suitable for short-lived scripts or tests where you already have a token (e.g., gcloud auth print-access-token).

pub async fn from_adc() -> Result<Self, Error>

Use Application Default Credentials via gcp_auth.

Tries, in order:

1. GOOGLE_APPLICATION_CREDENTIALS env var (service-account key file)
2. ~/.config/gcloud/application_default_credentials.json
3. GCE instance-metadata server
4. gcloud auth print-access-token

Tokens are cached and refreshed automatically by gcp_auth. This constructor is async because provider discovery may involve network I/O (metadata server probe).

Errors

Returns an error if no credential source is found or if the initial provider discovery fails.

pub fn from_env() -> Option<Self>

Read credentials from environment variables.

Checks, in order:

1. VERTEX_ACCESS_TOKEN – if set, constructs a from_token credential.
2. GOOGLE_APPLICATION_CREDENTIALS – if set, returns an from_adc credential.

Returns None when neither variable is set.

Panics

This method calls from_adc() synchronously by blocking on the current Tokio runtime when GOOGLE_APPLICATION_CREDENTIALS is set. It will panic if called outside a Tokio runtime context.

Trait Implementations

impl Clone for VertexCredentials

fn clone(&self) -> VertexCredentials

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for VertexCredentials

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.