[router][grpc] Fix streaming bugs: empty tool names, state pollution, and panics (#11373)

sgl-router/tests/common/mod.rs

@@ -4,6 +4,7 @@
 pub mod mock_mcp_server;
 pub mod mock_openai_server;
 pub mod mock_worker;
+pub mod streaming_helpers;
 pub mod test_app;
 
 use serde_json::json;

sgl-router/tests/common/streaming_helpers.rs

@@ -0,0 +1,134 @@
+//! Streaming Test Helpers
+//!
+//! Utilities for creating realistic streaming chunks that simulate
+//! how LLM tokens actually arrive (1-5 characters at a time).
+
+/// Split input into realistic char-level chunks (2-3 chars each for determinism)
+pub fn create_realistic_chunks(input: &str) -> Vec<String> {
+    let mut chunks = Vec::new();
+    let chars: Vec<char> = input.chars().collect();
+    let mut i = 0;
+
+    while i < chars.len() {
+        // Take 2-3 characters at a time (deterministic for testing)
+        let chunk_size = if i + 3 <= chars.len() && chars[i].is_ascii_alphanumeric() {
+            3 // Longer chunks for alphanumeric sequences
+        } else {
+            2 // Shorter chunks for special characters
+        };
+
+        let end = (i + chunk_size).min(chars.len());
+        let chunk: String = chars[i..end].iter().collect();
+        chunks.push(chunk);
+        i = end;
+    }
+
+    chunks
+}
+
+/// Split input at strategic positions to test edge cases
+/// This creates chunks that break at critical positions like after quotes, colons, etc.
+pub fn create_strategic_chunks(input: &str) -> Vec<String> {
+    let mut chunks = Vec::new();
+    let mut current = String::new();
+    let chars: Vec<char> = input.chars().collect();
+
+    for (i, &ch) in chars.iter().enumerate() {
+        current.push(ch);
+
+        // Break after strategic characters
+        let should_break = matches!(ch, '"' | ':' | ',' | '{' | '}' | '[' | ']')
+            || (i > 0 && chars[i-1] == '"' && ch == ' ') // Space after quote
+            || current.len() >= 5; // Max 5 chars per chunk
+
+        if should_break && !current.is_empty() {
+            chunks.push(current.clone());
+            current.clear();
+        }
+    }
+
+    if !current.is_empty() {
+        chunks.push(current);
+    }
+
+    chunks
+}
+
+/// Create the bug scenario chunks: `{"name": "` arrives in parts
+pub fn create_bug_scenario_chunks() -> Vec<&'static str> {
+    vec![
+        r#"{"#,
+        r#"""#,
+        r#"name"#,
+        r#"""#,
+        r#":"#,
+        r#" "#,
+        r#"""#,      // Bug occurs here: parser has {"name": "
+        r#"search"#, // Use valid tool name
+        r#"""#,
+        r#","#,
+        r#" "#,
+        r#"""#,
+        r#"arguments"#,
+        r#"""#,
+        r#":"#,
+        r#" "#,
+        r#"{"#,
+        r#"""#,
+        r#"query"#,
+        r#"""#,
+        r#":"#,
+        r#" "#,
+        r#"""#,
+        r#"test query"#,
+        r#"""#,
+        r#"}"#,
+        r#"}"#,
+    ]
+}
+
+#[cfg(test)]
+mod tests {
+    #[allow(unused_imports)]
+    use super::*;
+
+    #[test]
+    fn test_realistic_chunks() {
+        let input = r#"{"name": "test"}"#;
+        let chunks = create_realistic_chunks(input);
+
+        // Should have multiple chunks
+        assert!(chunks.len() > 3);
+
+        // Reconstructed should equal original
+        let reconstructed: String = chunks.join("");
+        assert_eq!(reconstructed, input);
+    }
+
+    #[test]
+    fn test_strategic_chunks_breaks_after_quotes() {
+        let input = r#"{"name": "value"}"#;
+        let chunks = create_strategic_chunks(input);
+
+        // Should break after quotes and colons
+        assert!(chunks.iter().any(|c| c.ends_with('"')));
+        assert!(chunks.iter().any(|c| c.ends_with(':')));
+
+        // Reconstructed should equal original
+        let reconstructed: String = chunks.join("");
+        assert_eq!(reconstructed, input);
+    }
+
+    #[test]
+    fn test_bug_scenario_chunks() {
+        let chunks = create_bug_scenario_chunks();
+        let reconstructed: String = chunks.join("");
+
+        // Should reconstruct to valid JSON
+        assert!(reconstructed.contains(r#"{"name": "search""#));
+
+        // The critical chunk sequence should be present (space after colon, then quote in next chunk)
+        let joined = chunks.join("|");
+        assert!(joined.contains(r#" |"#)); // The bug happens at {"name": " and then "
+    }
+}