example showing howto implement a custom flow, here opening the

default webbrowser with the oauth2 URL for the installed flow.

examples/custom_flow.rs

@@ -0,0 +1,64 @@
+//! Demonstrating how to create a custom Flow
+//! here we open the browser for the user, making the use of InstalledAppFlow more convenient as
+//! nothing has to be copy/pasted. Reason, the browser will open, the user accepts the requested
+//! scope by clicking through e.g. the google oauth2, after this is done a local webserver started
+//! by InstalledFlowAuthenticator will consume the token coming from the oauth2 server = no copy or
+//! paste needed to continue with the operation.
+use std::future::Future;
+use std::pin::Pin;
+use yup_oauth2::authenticator_delegate::{DefaultInstalledFlowDelegate, InstalledFlowDelegate};
+
+/// async function to be pinned by the `present_user_url` method of the trait
+/// we use the existing `DefaultInstalledFlowDelegate::present_user_url` method as a fallback for
+/// when the browser did not open for example, the user still see's the URL.
+async fn browser_user_url(url: &str, need_code: bool) -> Result<String, String> {
+    if webbrowser::open(url).is_ok() {
+        println!("webbrowser was successfully opened.");
+    }
+    let def_delegate = DefaultInstalledFlowDelegate;
+    def_delegate.present_user_url(url, need_code).await
+}
+
+/// our custom delegate struct we will implement a flow delegate trait for:
+/// in this case we will implement the `InstalledFlowDelegated` trait
+#[derive(Copy, Clone)]
+struct InstalledFlowBrowserDelegate;
+
+/// here we implement only the present_user_url method with the added webbrowser opening
+/// the other behaviour of the trait does not need to be changed.
+impl InstalledFlowDelegate for InstalledFlowBrowserDelegate {
+    /// the actual presenting of URL and browser opening happens in the function defined above here
+    /// we only pin it
+    fn present_user_url<'a>(
+        &'a self,
+        url: &'a str,
+        need_code: bool,
+    ) -> Pin<Box<dyn Future<Output = Result<String, String>> + Send + 'a>> {
+        Box::pin(browser_user_url(url, need_code))
+    }
+}
+
+#[tokio::main]
+async fn main() {
+    // Put your client secret in the working directory!
+    let sec = yup_oauth2::read_application_secret("client_secret.json")
+        .await
+        .expect("client secret couldn't be read.");
+    let auth = yup_oauth2::InstalledFlowAuthenticator::builder(
+        sec,
+        yup_oauth2::InstalledFlowReturnMethod::HTTPRedirect,
+    )
+    .persist_tokens_to_disk("tokencache.json")
+    // use our custom flow delegate instead of default
+    .flow_delegate(Box::new(InstalledFlowBrowserDelegate))
+    .build()
+    .await
+    .expect("InstalledFlowAuthenticator failed to build");
+
+    let scopes = &["https://www.googleapis.com/auth/drive.file"];
+
+    match auth.token(scopes).await {
+        Err(e) => println!("error: {:?}", e),
+        Ok(t) => println!("The token is {:?}", t),
+    }
+}