Skip serializing None fields in Gemini API (#29632)

Release Notes:

- N/A

crates/google_ai/src/google_ai.rs

@@ -124,8 +124,11 @@ pub struct GenerateContentRequest {
     #[serde(default, skip_serializing_if = "String::is_empty")]
     pub model: String,
     pub contents: Vec<Content>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub system_instruction: Option<SystemInstruction>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub generation_config: Option<GenerationConfig>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub safety_settings: Option<Vec<SafetySetting>>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub tools: Option<Vec<Tool>>,
@@ -136,19 +139,27 @@ pub struct GenerateContentRequest {
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct GenerateContentResponse {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub candidates: Option<Vec<GenerateContentCandidate>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub prompt_feedback: Option<PromptFeedback>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub usage_metadata: Option<UsageMetadata>,
 }
 
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct GenerateContentCandidate {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub index: Option<usize>,
     pub content: Content,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub finish_reason: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub finish_message: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub safety_ratings: Option<Vec<SafetyRating>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub citation_metadata: Option<CitationMetadata>,
 }
 
@@ -216,9 +227,13 @@ pub struct FunctionResponsePart {
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct CitationSource {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub start_index: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub end_index: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub uri: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub license: Option<String>,
 }
 
@@ -231,30 +246,44 @@ pub struct CitationMetadata {
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct PromptFeedback {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub block_reason: Option<String>,
     pub safety_ratings: Vec<SafetyRating>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub block_reason_message: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize, Default)]
 #[serde(rename_all = "camelCase")]
 pub struct UsageMetadata {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub prompt_token_count: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub cached_content_token_count: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub candidates_token_count: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub tool_use_prompt_token_count: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub thoughts_token_count: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub total_token_count: Option<usize>,
 }
 
 #[derive(Debug, Deserialize, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct GenerationConfig {
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub candidate_count: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub stop_sequences: Option<Vec<String>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub max_output_tokens: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub temperature: Option<f64>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub top_p: Option<f64>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub top_k: Option<usize>,
 }
 
@@ -292,16 +321,13 @@ pub enum HarmCategory {
 }
 
 #[derive(Debug, Serialize, Deserialize)]
+#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
 pub enum HarmBlockThreshold {
     #[serde(rename = "HARM_BLOCK_THRESHOLD_UNSPECIFIED")]
     Unspecified,
-    #[serde(rename = "BLOCK_LOW_AND_ABOVE")]
     BlockLowAndAbove,
-    #[serde(rename = "BLOCK_MEDIUM_AND_ABOVE")]
     BlockMediumAndAbove,
-    #[serde(rename = "BLOCK_ONLY_HIGH")]
     BlockOnlyHigh,
-    #[serde(rename = "BLOCK_NONE")]
     BlockNone,
 }