docs(guide): update setup guide with user feedback improvements (#3620)

This PR is a clone of #3233.

The [Rust Friction
Log](https://docs.google.com/document/d/1sQBFLKq1fmc-qJL1tHqsQvRjzsk_bp7xOEpXmNYy72U/edit?resourcekey=0-MMQyQ4t4DVkDzqNA1sp6IQ&tab=t.0#heading=h.kf1buofzahta)
gave users a chance to test the onboarding process and give us feedback.
This PR addresses the common issues users had.

Fixes b/429254171, b/429252054, b/429250702

Author: PhongChuong

guide/samples/src/gemini.rs

@@ -15,7 +15,7 @@
 //! Examples showing how to use the Vertex AI Gemini API.
 
 // ANCHOR: text-prompt
-pub async fn text_prompt(project_id: &str) -> crate::Result<()> {
+pub async fn text_prompt(project_id: &str) -> anyhow::Result<()> {
     // ANCHOR: text-prompt-client
     use google_cloud_aiplatform_v1 as vertexai;
     let client = vertexai::client::PredictionService::builder()
@@ -46,7 +46,7 @@ pub async fn text_prompt(project_id: &str) -> crate::Result<()> {
 // ANCHOR_END: text-prompt
 
 // ANCHOR: prompt-and-image
-pub async fn prompt_and_image(project_id: &str) -> crate::Result<()> {
+pub async fn prompt_and_image(project_id: &str) -> anyhow::Result<()> {
     // ANCHOR: prompt-and-image-client
     use google_cloud_aiplatform_v1 as vertexai;
     let client = vertexai::client::PredictionService::builder()

guide/samples/tests/driver.rs

@@ -19,13 +19,13 @@ mod driver {
     const SECRET_ID_LENGTH: usize = 32;
 
     #[tokio::test(flavor = "multi_thread")]
-    async fn gemini_text_prompt() -> user_guide_samples::Result<()> {
+    async fn gemini_text_prompt() -> anyhow::Result<()> {
         let project_id = std::env::var("GOOGLE_CLOUD_PROJECT").unwrap();
         user_guide_samples::gemini::text_prompt(&project_id).await
     }
 
     #[tokio::test(flavor = "multi_thread")]
-    async fn gemini_prompt_and_image() -> user_guide_samples::Result<()> {
+    async fn gemini_prompt_and_image() -> anyhow::Result<()> {
         let project_id = std::env::var("GOOGLE_CLOUD_PROJECT").unwrap();
         user_guide_samples::gemini::prompt_and_image(&project_id).await
     }

guide/samples/tests/initialize_client.rs

@@ -13,9 +13,7 @@
 // limitations under the License.
 
 // [START test_only_snippet] ANCHOR: all
-pub type Result = std::result::Result<(), Box<dyn std::error::Error>>;
-
-pub async fn initialize_client(project_id: &str) -> Result {
+pub async fn initialize_client(project_id: &str) -> anyhow::Result<()> {
     // [START test_only] ANCHOR: use
     use google_cloud_secretmanager_v1::client::SecretManagerService;
     // [END test_only] ANCHOR_END: use
@@ -44,14 +42,21 @@ pub async fn initialize_client(project_id: &str) -> Result {
 
     Ok(())
 }
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    let project_id = std::env::args().nth(1).unwrap();
+
+    initialize_client(&project_id).await
+}
 // [END test_only_snippet] ANCHOR_END: all
 
 #[cfg(all(test, feature = "run-integration-tests"))]
 mod tests {
     use super::*;
 
     #[tokio::test(flavor = "multi_thread")]
-    async fn driver() -> Result {
+    async fn driver() -> anyhow::Result<()> {
         let project_id = std::env::var("GOOGLE_CLOUD_PROJECT").unwrap();
         initialize_client(&project_id).await
     }

guide/src/setting_up_rust_on_cloud_shell.md

@@ -95,6 +95,20 @@ Cloud Shell.
    [create a secret] and rerun the program, and you should see the secret
    printed in the output.
 
+   You might see a "no space left on device" error. Run the following to remove
+   build artifacts:
+
+   ```shell
+   cargo clean
+   ```
+
+   Alternatively, you can build in release mode, which should also use less disk
+   space:
+
+   ```shell
+   cargo build --release
+   ```
+
 <!-- markdownlint-enable MD029 -->
 
 [authorize cloud shell]: https://cloud.google.com/shell/docs/auth