Merge pull request #26 from andreclaudino/feature/new-from-custom-fil…

…e-path

Expose a function create an instance from a path instead of a variable

README.md

@@ -58,6 +58,14 @@ let authentication_manager = gcp_auth::init().await?;
 let token = authentication_manager.get_token(&scopes).await?;
 ```
 
+You may instantiate `authentication_manager` from a credentials file path using the method `from_credentials_file`:
+
+```async
+ // `credentials_path` variable is the path for the credentials `.json` file.
+ let authentication_manager = gcp_auth::from_credentials_file(credentials_path).await?;
+ let token = authentication_manager.get_token().await?;
+```
+
 ## Local user authentication
 
 This authentication method allows developers to authenticate again GCP when

src/custom_service_account.rs

@@ -10,11 +10,7 @@ pub struct CustomServiceAccount {
 }
 
 impl CustomServiceAccount {
-    const GOOGLE_APPLICATION_CREDENTIALS: &'static str = "GOOGLE_APPLICATION_CREDENTIALS";
-
-    pub async fn new() -> Result<Self, Error> {
-        let path = std::env::var(Self::GOOGLE_APPLICATION_CREDENTIALS)
-            .map_err(|_| Error::AplicationProfileMissing)?;
+    pub async fn from_file(path: &str) -> Result<Self, Error> {
         let credentials = ApplicationCredentials::from_file(path).await?;
         Ok(Self {
             credentials,

src/lib.rs

@@ -37,6 +37,14 @@
 //! let authentication_manager = gcp_auth::init().await?;
 //! let token = authentication_manager.get_token().await?;
 //! ```
+//! You may instantiate `authentication_manager` from a credentials file path using the method `from_credentials_file`:
+//!
+//! ```async
+//! // `credentials_path` variable is the path for the credentials `.json` file.
+//! let authentication_manager = gcp_auth::from_credentials_file(credentials_path).await?;
+//! let token = authentication_manager.get_token().await?;
+//! ```
+//!
 //! # Local user authentication
 //! This authentication method allows developers to authenticate again GCP services when developign locally.
 //! The method is intended only for development. Credentials can be set-up using `gcloud auth` utility.
@@ -74,17 +82,17 @@ pub use types::Token;
 use hyper::Client;
 use hyper_rustls::HttpsConnector;
 
-/// Initialize GCP authentication
+/// Initialize GCP authentication based on a credentials file
 ///
 /// Returns `AuthenticationManager` which can be used to obtain tokens
-pub async fn init() -> Result<AuthenticationManager, Error> {
+pub async fn from_credentials_file(path: &str) -> Result<AuthenticationManager, Error> {
     #[cfg(feature = "webpki-roots")]
     let https = HttpsConnector::with_webpki_roots();
     #[cfg(not(feature = "webpki-roots"))]
     let https = HttpsConnector::with_native_roots();
 
     let client = Client::builder().build::<_, hyper::Body>(https);
-    let custom = custom_service_account::CustomServiceAccount::new().await;
+    let custom = custom_service_account::CustomServiceAccount::from_file(path).await;
     if let Ok(service_account) = custom {
         return Ok(AuthenticationManager {
             client,
@@ -111,3 +119,14 @@ pub async fn init() -> Result<AuthenticationManager, Error> {
         Box::new(user.unwrap_err()),
     ))
 }
+
+/// Initialize GCP authentication
+///
+/// Returns `AuthenticationManager` which can be used to obtain tokens
+pub async fn init() -> Result<AuthenticationManager, Error> {
+    const GOOGLE_APPLICATION_CREDENTIALS: &'static str = "GOOGLE_APPLICATION_CREDENTIALS";
+    let path = std::env::var(GOOGLE_APPLICATION_CREDENTIALS)
+            .map_err(|_| Error::AplicationProfileMissing)?;
+
+    from_credentials_file(&path).await
+}