[router] add qwen tool parser (#9623)

Co-authored-by: Chang Su <chang.s.su@oracle.com>

sgl-router/src/tool_parser/mod.rs

@@ -5,7 +5,7 @@ pub mod errors;
 pub mod json_parser;
 pub mod mistral_parser;
 pub mod partial_json;
-
+pub mod qwen_parser;
 pub mod registry;
 pub mod state;
 pub mod traits;
@@ -18,6 +18,7 @@ mod tests;
 pub use errors::{ToolParserError, ToolParserResult};
 pub use json_parser::JsonParser;
 pub use mistral_parser::MistralParser;
+pub use qwen_parser::QwenParser;
 pub use registry::ParserRegistry;
 pub use state::{ParsePhase, ParseState};
 pub use traits::{PartialJsonParser, ToolParser};

sgl-router/src/tool_parser/qwen_parser.rs

+use async_trait::async_trait;
+use regex::Regex;
+use serde_json::Value;
+
+use crate::tool_parser::{
+    errors::{ToolParserError, ToolParserResult},
+    partial_json::PartialJson,
+    state::ParseState,
+    traits::ToolParser,
+    types::{FunctionCall, StreamResult, ToolCall},
+};
+
+/// Qwen format parser for tool calls
+///
+/// Handles the Qwen 2.5/3 specific format:
+/// `<tool_call>\n{"name": "func", "arguments": {...}}\n</tool_call>`
+///
+/// Features:
+/// - XML-style tags with JSON content
+/// - Support for multiple sequential tool calls
+/// - Newline-aware parsing
+pub struct QwenParser {
+    /// Parser for handling incomplete JSON during streaming
+    partial_json: PartialJson,
+    /// Regex for extracting tool calls
+    extractor: Regex,
+}
+
+impl QwenParser {
+    /// Create a new Qwen parser
+    pub fn new() -> Self {
+        // Use (?s) flag for DOTALL mode to handle newlines
+        let pattern = r"(?s)<tool_call>\n(.*?)\n</tool_call>";
+        let extractor = Regex::new(pattern).expect("Valid regex pattern");
+
+        Self {
+            partial_json: PartialJson::default(),
+            extractor,
+        }
+    }
+
+    /// Extract all tool call blocks from text
+    fn extract_tool_calls<'a>(&self, text: &'a str) -> Vec<&'a str> {
+        self.extractor
+            .captures_iter(text)
+            .filter_map(|cap| cap.get(1).map(|m| m.as_str()))
+            .collect()
+    }
+
+    /// Parse a single JSON object into a ToolCall
+    fn parse_single_object(&self, obj: &Value, index: usize) -> ToolParserResult<Option<ToolCall>> {
+        let name = obj.get("name").and_then(|v| v.as_str());
+
+        if let Some(name) = name {
+            // Get arguments - Qwen uses "arguments" key
+            let empty_obj = Value::Object(serde_json::Map::new());
+            let args = obj.get("arguments").unwrap_or(&empty_obj);
+
+            // Convert arguments to JSON string
+            let arguments = serde_json::to_string(args)
+                .map_err(|e| ToolParserError::ParsingFailed(e.to_string()))?;
+
+            // Generate ID with index for multiple tools
+            let id = format!("qwen_call_{}", index);
+
+            Ok(Some(ToolCall {
+                id,
+                r#type: "function".to_string(),
+                function: FunctionCall {
+                    name: name.to_string(),
+                    arguments,
+                },
+            }))
+        } else {
+            Ok(None)
+        }
+    }
+
+    /// Check if text contains Qwen tool markers
+    fn has_tool_markers(&self, text: &str) -> bool {
+        text.contains("<tool_call>")
+    }
+
+    /// Find the start position of a tool call
+    fn find_tool_start(&self, text: &str) -> Option<usize> {
+        text.find("<tool_call>\n")
+    }
+
+    /// Find the end position of a tool call
+    fn find_tool_end(&self, text: &str, start_pos: usize) -> Option<usize> {
+        let search_from = start_pos + "<tool_call>\n".len();
+        text[search_from..]
+            .find("\n</tool_call>")
+            .map(|pos| search_from + pos + "\n</tool_call>".len())
+    }
+
+    /// Check if buffer ends with a partial token
+    fn ends_with_partial_token(&self, buffer: &str) -> Option<usize> {
+        // Check for partial start token
+        let start_token = "<tool_call>\n";
+        // Use inclusive range to check if entire buffer could be a prefix
+        for i in 1..=start_token.len().min(buffer.len()) {
+            if start_token.starts_with(&buffer[buffer.len() - i..]) {
+                return Some(i);
+            }
+        }
+
+        // Check for partial end token
+        let end_token = "\n</tool_call>";
+        // Use inclusive range to check if entire buffer could be a prefix
+        (1..=end_token.len().min(buffer.len()))
+            .find(|&i| end_token.starts_with(&buffer[buffer.len() - i..]))
+    }
+}
+
+impl Default for QwenParser {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[async_trait]
+impl ToolParser for QwenParser {
+    async fn parse_complete(&self, text: &str) -> ToolParserResult<Vec<ToolCall>> {
+        // Check if text contains Qwen format
+        if !self.has_tool_markers(text) {
+            return Ok(vec![]);
+        }
+
+        // Extract all tool call blocks
+        let tool_blocks = self.extract_tool_calls(text);
+        let mut tools = Vec::new();
+
+        for (index, json_str) in tool_blocks.iter().enumerate() {
+            // Parse each JSON block
+            match serde_json::from_str::<Value>(json_str.trim()) {
+                Ok(value) => {
+                    if let Some(tool) = self.parse_single_object(&value, index)? {
+                        tools.push(tool);
+                    }
+                }
+                Err(_) => {
+                    // Skip malformed JSON blocks
+                    continue;
+                }
+            }
+        }
+
+        Ok(tools)
+    }
+
+    async fn parse_incremental(
+        &self,
+        chunk: &str,
+        state: &mut ParseState,
+    ) -> ToolParserResult<StreamResult> {
+        state.buffer.push_str(chunk);
+
+        // Check for partial token at end of buffer
+        if let Some(_partial_len) = self.ends_with_partial_token(&state.buffer) {
+            // Hold back the partial token
+            return Ok(StreamResult::Incomplete);
+        }
+
+        // Check if we have the start marker
+        if !self.has_tool_markers(&state.buffer) {
+            return Ok(StreamResult::Incomplete);
+        }
+
+        // Find start and end positions
+        if let Some(start_pos) = self.find_tool_start(&state.buffer) {
+            // Check if we have the complete tool call
+            if let Some(end_pos) = self.find_tool_end(&state.buffer, start_pos) {
+                // Extract the JSON content
+                let json_start = start_pos + "<tool_call>\n".len();
+                let json_end = end_pos - "\n</tool_call>".len();
+                let json_str = &state.buffer[json_start..json_end];
+
+                // Parse the complete JSON
+                match serde_json::from_str::<Value>(json_str.trim()) {
+                    Ok(value) => {
+                        if let Some(tool) = self.parse_single_object(&value, 0)? {
+                            // Clear the consumed part from buffer using drain for efficiency
+                            state.buffer.drain(..end_pos);
+                            return Ok(StreamResult::ToolComplete(tool));
+                        }
+                    }
+                    Err(_) => {
+                        // JSON parsing failed, might be incomplete
+                    }
+                }
+            } else {
+                // We have start but no end yet - try partial parsing
+                let json_start = start_pos + "<tool_call>\n".len();
+                let partial_json = &state.buffer[json_start..];
+
+                // Remove trailing newline if present (might be start of end token)
+                let partial_json = partial_json.trim_end();
+
+                // Try to parse with partial JSON parser
+                match self.partial_json.parse_value(partial_json) {
+                    Ok((value, _consumed)) => {
+                        // Extract tool name if available
+                        if let Some(name) = value.get("name").and_then(|v| v.as_str()) {
+                            // Check if we've already sent the name
+                            if !state.in_string {
+                                state.in_string = true; // Use as flag for "name sent"
+                                return Ok(StreamResult::ToolName {
+                                    index: 0,
+                                    name: name.to_string(),
+                                });
+                            }
+
+                            // Check for arguments
+                            if let Some(args) = value.get("arguments") {
+                                if let Ok(args_str) = serde_json::to_string(args) {
+                                    return Ok(StreamResult::ToolArguments {
+                                        index: 0,
+                                        arguments: args_str,
+                                    });
+                                }
+                            }
+                        }
+                    }
+                    Err(_) => {
+                        // Failed to parse even as partial JSON
+                        // Keep buffering
+                    }
+                }
+            }
+        }
+
+        Ok(StreamResult::Incomplete)
+    }
+
+    fn detect_format(&self, text: &str) -> bool {
+        // Check if text contains Qwen-specific markers. If not, it's not this format.
+        if !self.has_tool_markers(text) {
+            return false;
+        }
+
+        // Try to extract tool calls to see if we have a complete, valid one.
+        let tool_blocks = self.extract_tool_calls(text);
+        for json_str in &tool_blocks {
+            if let Ok(value) = serde_json::from_str::<Value>(json_str.trim()) {
+                if let Some(obj) = value.as_object() {
+                    if obj.contains_key("name") && obj.contains_key("arguments") {
+                        // Found a valid, complete tool call.
+                        return true;
+                    }
+                }
+            }
+        }
+
+        // If we have the marker but no valid complete tool call,
+        // it could be a partial stream. We should detect this as the format.
+        true
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn test_parse_qwen_format() {
+        let parser = QwenParser::new();
+        let input = r#"<tool_call>
+{"name": "get_weather", "arguments": {"location": "Beijing", "units": "celsius"}}
+</tool_call>"#;
+
+        let result = parser.parse_complete(input).await.unwrap();
+        assert_eq!(result.len(), 1);
+        assert_eq!(result[0].function.name, "get_weather");
+        assert!(result[0].function.arguments.contains("Beijing"));
+    }
+
+    #[tokio::test]
+    async fn test_parse_multiple_tools() {
+        let parser = QwenParser::new();
+        let input = r#"<tool_call>
+{"name": "search", "arguments": {"query": "rust programming"}}
+</tool_call>
+<tool_call>
+{"name": "calculate", "arguments": {"expression": "2 + 2"}}
+</tool_call>"#;
+
+        let result = parser.parse_complete(input).await.unwrap();
+        assert_eq!(result.len(), 2);
+        assert_eq!(result[0].function.name, "search");
+        assert_eq!(result[1].function.name, "calculate");
+    }
+
+    #[tokio::test]
+    async fn test_with_normal_text() {
+        let parser = QwenParser::new();
+        let input = r#"Let me help you with that.
+<tool_call>
+{"name": "get_info", "arguments": {"topic": "Rust"}}
+</tool_call>
+Here are the results."#;
+
+        let result = parser.parse_complete(input).await.unwrap();
+        assert_eq!(result.len(), 1);
+        assert_eq!(result[0].function.name, "get_info");
+    }
+
+    #[tokio::test]
+    async fn test_nested_json_structures() {
+        let parser = QwenParser::new();
+        let input = r#"<tool_call>
+{
+    "name": "process_data",
+    "arguments": {
+        "data": {
+            "nested": {
+                "array": [1, 2, 3],
+                "object": {"key": "value"}
+            }
+        }
+    }
+}
+</tool_call>"#;
+
+        let result = parser.parse_complete(input).await.unwrap();
+        assert_eq!(result.len(), 1);
+        assert_eq!(result[0].function.name, "process_data");
+        assert!(result[0].function.arguments.contains("nested"));
+    }
+
+    #[test]
+    fn test_detect_format() {
+        let parser = QwenParser::new();
+
+        assert!(parser.detect_format(
+            r#"<tool_call>
+{"name": "test", "arguments": {}}
+</tool_call>"#
+        ));
+
+        assert!(parser.detect_format(
+            r#"Text before <tool_call>
+{"name": "test", "arguments": {}}
+</tool_call> text after"#
+        ));
+
+        assert!(!parser.detect_format(r#"{"name": "test", "arguments": {}}"#));
+        assert!(!parser.detect_format("plain text"));
+
+        // Partial format should still be detected
+        assert!(parser.detect_format("<tool_call>"));
+    }
+
+    #[tokio::test]
+    async fn test_streaming_partial() {
+        let parser = QwenParser::new();
+        let mut state = ParseState::new();
+
+        // Simulate streaming chunks
+        let chunks = vec![
+            "<tool_call>\n",
+            r#"{"name": "search","#,
+            r#" "arguments": {"query":"#,
+            r#" "rust"}}"#,
+            "\n</tool_call>",
+        ];
+
+        let mut found_name = false;
+        let mut found_complete = false;
+
+        for chunk in chunks {
+            let result = parser.parse_incremental(chunk, &mut state).await.unwrap();
+
+            match result {
+                StreamResult::ToolName { name, .. } => {
+                    assert_eq!(name, "search");
+                    found_name = true;
+                }
+                StreamResult::ToolComplete(tool) => {
+                    assert_eq!(tool.function.name, "search");
+                    found_complete = true;
+                }
+                _ => {}
+            }
+        }
+
+        assert!(found_name || found_complete); // At least one should be found
+    }
+}

sgl-router/src/tool_parser/registry.rs

 use crate::tool_parser::json_parser::JsonParser;
+use crate::tool_parser::mistral_parser::MistralParser;
+use crate::tool_parser::qwen_parser::QwenParser;
 use crate::tool_parser::traits::ToolParser;
 use std::collections::HashMap;
 use std::sync::Arc;
@@ -97,7 +99,11 @@ impl ParserRegistry {
         // JSON parser - most common format
         self.register_parser("json", Arc::new(JsonParser::new()));
 
-        // Note: Additional parsers (mistral, qwen, llama) will be added in later phases
+        // Mistral parser - [TOOL_CALLS] [...] format
+        self.register_parser("mistral", Arc::new(MistralParser::new()));
+
+        // Qwen parser - <tool_call>...</tool_call> format
+        self.register_parser("qwen", Arc::new(QwenParser::new()));
     }
 
     /// Register default model mappings