feat(gcs): allow unauthenticated requests

core/src/services/gcs/backend.rs

@@ -66,6 +66,10 @@ pub struct GcsConfig {
     pub predefined_acl: Option<String>,
     /// The default storage class used by gcs.
     pub default_storage_class: Option<String>,
+    /// Explicitly disable authentication
+    ///
+    /// Used for testing purposes against storage emulators.
+    pub no_authentication: bool,
 }
 
 impl Debug for GcsConfig {
@@ -234,6 +238,14 @@ impl GcsBuilder {
         };
         self
     }
+
+    /// Explicitly disable authentication.
+    ///
+    /// This is typically only done for testing purposes against storage emulators.
+    pub fn no_authentication(mut self) -> Self {
+        self.config.no_authentication = true;
+        self
+    }
 }
 
 impl Builder for GcsBuilder {
@@ -317,6 +329,7 @@ impl Builder for GcsBuilder {
                 credential_loader: cred_loader,
                 predefined_acl: self.config.predefined_acl.clone(),
                 default_storage_class: self.config.default_storage_class.clone(),
+                no_authentication: self.config.no_authentication,
             }),
         };
 

core/src/services/gcs/core.rs

@@ -57,6 +57,8 @@ pub struct GcsCore {
 
     pub predefined_acl: Option<String>,
     pub default_storage_class: Option<String>,
+
+    pub no_authentication: bool,
 }
 
 impl Debug for GcsCore {
@@ -89,14 +91,18 @@ impl GcsCore {
         }
     }
 
-    fn load_credential(&self) -> Result<GoogleCredential> {
+    fn load_credential(&self) -> Result<Option<GoogleCredential>> {
+        if self.no_authentication {
+            return Ok(None);
+        }
+
         let cred = self
             .credential_loader
             .load()
             .map_err(new_request_credential_error)?;
 
         if let Some(cred) = cred {
-            Ok(cred)
+            Ok(Some(cred))
         } else {
             Err(Error::new(
                 ErrorKind::ConfigInvalid,
@@ -106,6 +112,9 @@ impl GcsCore {
     }
 
     pub async fn sign<T>(&self, req: &mut Request<T>) -> Result<()> {
+        if self.no_authentication {
+            return Ok(());
+        }
         let cred = self.load_token().await?;
 
         self.signer
@@ -124,11 +133,13 @@ impl GcsCore {
     }
 
     pub async fn sign_query<T>(&self, req: &mut Request<T>, duration: Duration) -> Result<()> {
-        let cred = self.load_credential()?;
-
-        self.signer
-            .sign_query(req, duration, &cred)
-            .map_err(new_request_sign_error)?;
+        if let Some(cred) = self.load_credential()? {
+            self.signer
+                .sign_query(req, duration, &cred)
+                .map_err(new_request_sign_error)?;
+        } else {
+            return Ok(());
+        }
 
         // Always remove host header, let users' client to set it based on HTTP
         // version.