[DISCO-4084] Handle 204 as a successful empty response

components/merino/src/suggest/error.rs

@@ -30,10 +30,6 @@ pub enum Error {
     #[error("Error sending request: {0}")]
     Request(#[from] viaduct::ViaductError),
 
-    /// The server returned no content (HTTP 204), meaning no suggestions were available.
-    #[error("No content ({code}): {message}")]
-    NoContent { code: u16, message: String },
-
     /// The server rejected the request due to malformed syntax (HTTP 400).
     #[error("Bad request ({code}): {message}")]
     BadRequest { code: u16, message: String },
@@ -64,8 +60,7 @@ impl GetErrorHandling for Error {
             Self::Validation { code, .. }
             | Self::Server { code, .. }
             | Self::Unexpected { code, .. }
-            | Self::BadRequest { code, .. }
-            | Self::NoContent { code, .. } => {
+            | Self::BadRequest { code, .. } => {
                 ErrorHandling::convert(MerinoSuggestApiError::Other {
                     code: Some(*code),
                     reason: self.to_string(),

components/merino/src/suggest/http.rs

@@ -27,7 +27,7 @@ pub trait HttpClientTrait {
         query: &str,
         options: SuggestQueryParams<'_>,
         endpoint_url: Url,
-    ) -> Result<Response>;
+    ) -> Result<Option<Response>>;
 }
 
 fn build_suggest_url(query: &str, options: &SuggestQueryParams<'_>, endpoint_url: Url) -> Url {
@@ -67,7 +67,7 @@ impl HttpClientTrait for HttpClient {
         query: &str,
         options: SuggestQueryParams<'_>,
         endpoint_url: Url,
-    ) -> Result<Response> {
+    ) -> Result<Option<Response>> {
         let url = build_suggest_url(query, &options, endpoint_url);
 
         let client = Client::with_ohttp_channel("merino", ClientSettings::default())?;
@@ -81,28 +81,24 @@ impl HttpClientTrait for HttpClient {
 
         let response = client.send_sync(request)?;
         let status = response.status;
-        let message = response.text().to_string();
         match status {
-            200 => Ok(response),
-            204 => Err(Error::NoContent {
-                code: status,
-                message,
-            }),
+            200 => Ok(Some(response)),
+            204 => Ok(None),
             400 => Err(Error::BadRequest {
                 code: status,
-                message,
+                message: response.text().to_string(),
             }),
             422 => Err(Error::Validation {
                 code: status,
-                message,
+                message: response.text().to_string(),
             }),
             500..=599 => Err(Error::Server {
                 code: status,
-                message,
+                message: response.text().to_string(),
             }),
             _ => Err(Error::Unexpected {
                 code: status,
-                message,
+                message: response.text().to_string(),
             }),
         }
     }

components/merino/src/suggest/mod.rs

@@ -77,14 +77,19 @@ impl SuggestClient {
 
     /// Fetches suggestions from the merino suggest endpoint for the given query.
     ///
-    /// Returns the raw JSON response body as a string.
+    /// Returns the raw JSON response body as a string, or `None` if the server
+    /// returned HTTP 204 (no suggestions available for weather).
     #[handle_error(Error)]
-    pub fn get_suggestions(&self, query: String, options: SuggestOptions) -> ApiResult<String> {
+    pub fn get_suggestions(
+        &self,
+        query: String,
+        options: SuggestOptions,
+    ) -> ApiResult<Option<String>> {
         let response = self
             .inner
             .get_suggestions(query.as_str(), options, &self.endpoint_url)?;
 
-        Ok(response.text().to_string())
+        Ok(response.map(|r| r.text().to_string()))
     }
 }
 
@@ -102,7 +107,7 @@ impl<T: http::HttpClientTrait> SuggestClientInner<T> {
         query: &str,
         options: SuggestOptions,
         endpoint_url: &Url,
-    ) -> Result<viaduct::Response> {
+    ) -> Result<Option<viaduct::Response>> {
         let providers = options
             .providers
             .filter(|v| !v.is_empty())

components/merino/src/suggest/tests.rs

@@ -57,8 +57,8 @@ impl http::HttpClientTrait for FakeHttpClientSuccess {
         _query: &str,
         _options: http::SuggestQueryParams<'_>,
         _endpoint_url: Url,
-    ) -> Result<Response> {
-        Ok(make_response(200, SAMPLE_RESPONSE))
+    ) -> Result<Option<Response>> {
+        Ok(Some(make_response(200, SAMPLE_RESPONSE)))
     }
 }
 
@@ -70,7 +70,7 @@ impl http::HttpClientTrait for FakeHttpClientValidationError {
         _query: &str,
         _options: http::SuggestQueryParams<'_>,
         _endpoint_url: Url,
-    ) -> Result<Response> {
+    ) -> Result<Option<Response>> {
         Err(Error::Validation {
             code: 422,
             message: "Invalid input".to_string(),
@@ -86,7 +86,7 @@ impl http::HttpClientTrait for FakeHttpClientServerError {
         _query: &str,
         _options: http::SuggestQueryParams<'_>,
         _endpoint_url: Url,
-    ) -> Result<Response> {
+    ) -> Result<Option<Response>> {
         Err(Error::Server {
             code: 500,
             message: "Internal server error".to_string(),
@@ -102,14 +102,27 @@ impl http::HttpClientTrait for FakeHttpClientBadRequestError {
         _query: &str,
         _options: http::SuggestQueryParams<'_>,
         _endpoint_url: Url,
-    ) -> Result<Response> {
+    ) -> Result<Option<Response>> {
         Err(Error::BadRequest {
             code: 400,
             message: "Bad request".to_string(),
         })
     }
 }
 
+struct FakeHttpClientNoContent;
+
+impl http::HttpClientTrait for FakeHttpClientNoContent {
+    fn make_suggest_request(
+        &self,
+        _query: &str,
+        _options: http::SuggestQueryParams<'_>,
+        _endpoint_url: Url,
+    ) -> Result<Option<Response>> {
+        Ok(None)
+    }
+}
+
 struct FakeCapturingClient {
     captured_url: std::sync::Arc<std::sync::Mutex<Option<Url>>>,
 }
@@ -120,9 +133,9 @@ impl http::HttpClientTrait for FakeCapturingClient {
         _query: &str,
         _options: http::SuggestQueryParams<'_>,
         endpoint_url: Url,
-    ) -> Result<Response> {
+    ) -> Result<Option<Response>> {
         *self.captured_url.lock().unwrap() = Some(endpoint_url);
-        Ok(make_response(200, "{}"))
+        Ok(Some(make_response(200, "{}")))
     }
 }
 
@@ -136,7 +149,7 @@ impl http::HttpClientTrait for FakeCapturingClientWithParams {
         query: &str,
         options: http::SuggestQueryParams<'_>,
         mut endpoint_url: Url,
-    ) -> Result<Response> {
+    ) -> Result<Option<Response>> {
         {
             let mut params = endpoint_url.query_pairs_mut();
             params.append_pair("q", query);
@@ -148,7 +161,7 @@ impl http::HttpClientTrait for FakeCapturingClientWithParams {
             }
         }
         *self.captured_url.lock().unwrap() = Some(endpoint_url);
-        Ok(make_response(200, "{}"))
+        Ok(Some(make_response(200, "{}")))
     }
 }
 
@@ -162,7 +175,20 @@ fn test_get_suggestions_success() {
     );
 
     assert!(result.is_ok());
-    assert_eq!(result.unwrap().text(), SAMPLE_RESPONSE);
+    assert_eq!(result.unwrap().unwrap().text(), SAMPLE_RESPONSE);
+}
+
+#[test]
+fn test_get_suggestions_no_content() {
+    let client_inner = SuggestClientInner::new_with_client(FakeHttpClientNoContent);
+    let result = client_inner.get_suggestions(
+        "apple",
+        default_options(),
+        &Url::parse("https://merino.services.mozilla.com/api/v1/suggest").unwrap(),
+    );
+
+    assert!(result.is_ok());
+    assert!(result.unwrap().is_none());
 }
 
 #[test]

examples/merino-cli/src/main.rs

@@ -146,9 +146,13 @@ fn main() -> Result<()> {
                 request_type,
                 accept_language,
             };
-            let response = client.get_suggestions(query, options)?;
-            let json: serde_json::Value = serde_json::from_str(&response)?;
-            println!("{}", serde_json::to_string_pretty(&json)?);
+            match client.get_suggestions(query, options)? {
+                Some(response) => {
+                    let json: serde_json::Value = serde_json::from_str(&response)?;
+                    println!("{}", serde_json::to_string_pretty(&json)?);
+                }
+                None => println!("No suggestions available (204 No Content)"),
+            }
         }
     }