Rewrite JSON tool call filter with clean state machine

Fixes bug where JSON tool calls were printed as text due to chunking issues.

Changes:
- Complete rewrite of filter_json.rs with 3-state machine:
  - Streaming: normal pass-through, watches for newline + whitespace + {
  - Buffering: confirms/denies tool pattern with ~20 char buffer
  - Suppressing: string-aware brace counting until balanced
- Character-by-character processing eliminates chunk boundary issues
- Proper handling of } inside JSON strings (was causing premature exit)
- Detects truncated JSON followed by complete JSON (LLM retry case)
- Removed regex dependency, simpler pattern matching
- Added 59 stress tests covering malformed JSON, partial patterns,
  streaming edge cases, adversarial inputs, and real-world patterns

All 86 filter_json tests pass.
This commit is contained in:
Dhanji R. Prasanna
2026-01-09 14:05:11 +11:00
parent 49b27b0cbc
commit d96d8c1d90
2 changed files with 985 additions and 407 deletions

View File

@@ -1,78 +1,160 @@
//! JSON tool call filtering for streaming LLM responses. //! JSON tool call filtering for streaming LLM responses.
//! //!
//! This module filters out JSON tool calls from LLM output streams while preserving //! This module filters out JSON tool calls from LLM output streams while preserving
//! regular text content. It uses a state machine to handle streaming chunks. //! regular text content. It uses a simple state machine optimized for streaming.
//! //!
//! # Design //! # Design
//! //!
//! The filter detects tool calls by looking for JSON objects that start with `{"tool":` //! The filter uses three states:
//! at the beginning of a line. It uses brace counting to find the complete JSON object //! - **Streaming**: Normal pass-through mode. Watches for newline + whitespace + `{`
//! and removes it from the output stream. //! - **Buffering**: Saw potential tool call start, buffering to confirm/deny
//! - **Suppressing**: Confirmed tool call, counting braces (string-aware) to find end
//! //!
//! # Known Edge Cases //! The key insight is that we only need to buffer a small amount (around 12 chars)
//! //! to confirm whether `{` starts a tool call pattern like `{"tool":`.
//! 1. **Brace counting without string awareness in main loop**: The main filtering loop
//! counts braces without considering whether they're inside JSON strings. This can
//! cause premature exit from suppression mode if a string contains `}`.
//!
//! 2. **Tool calls not at line start**: Tool calls that don't start at the beginning
//! of a line (after optional whitespace) won't be detected.
//!
//! 3. **Streaming chunk boundaries**: If a tool call pattern is split across chunks
//! (e.g., `{"to` in one chunk and `ol":` in the next), detection may fail.
use regex::Regex;
use std::cell::RefCell; use std::cell::RefCell;
use tracing::debug; use tracing::debug;
/// Maximum chars needed to confirm/deny a tool call pattern.
/// Pattern is: { + optional whitespace + "tool" + optional whitespace + : + optional whitespace + "
/// Realistically: `{"tool":"` = 9 chars, with whitespace maybe 15 max
const MAX_BUFFER_FOR_DETECTION: usize = 20;
// Thread-local state for tracking JSON tool call suppression // Thread-local state for tracking JSON tool call suppression
thread_local! { thread_local! {
static JSON_TOOL_STATE: RefCell<JsonToolState> = RefCell::new(JsonToolState::new()); static JSON_TOOL_STATE: RefCell<FilterState> = RefCell::new(FilterState::new());
} }
/// Internal state for tracking JSON tool call filtering across streaming chunks. /// The three possible states of the filter
#[derive(Debug, Clone, PartialEq)]
enum State {
/// Normal streaming - pass through content, watch for newline + whitespace + {
Streaming,
/// Saw potential start, buffering to confirm/deny tool pattern
Buffering,
/// Confirmed tool call, suppressing until braces balance
Suppressing,
}
/// Internal state for the filter
#[derive(Debug, Clone)] #[derive(Debug, Clone)]
struct JsonToolState { struct FilterState {
/// True when actively suppressing a confirmed tool call state: State,
suppression_mode: bool, /// Buffer for potential tool call detection (Buffering state)
/// True when buffering potential JSON (saw { but not yet confirmed as tool call)
potential_json_mode: bool,
/// Tracks nesting depth of braces within JSON
brace_depth: i32,
buffer: String, buffer: String,
json_start_in_buffer: Option<usize>, // Position where confirmed JSON tool call starts /// Brace depth for JSON tracking (Suppressing state) - string-aware
content_returned_up_to: usize, // Track how much content we've already returned brace_depth: i32,
potential_json_start: Option<usize>, // Where the potential JSON started /// Are we inside a JSON string? (for proper brace counting)
in_string: bool,
/// Was the previous char a backslash? (for escape handling)
escape_next: bool,
/// Track if we just saw a newline (to detect line-start patterns)
at_line_start: bool,
/// Whitespace seen after newline (before potential {)
pending_whitespace: String,
} }
impl JsonToolState { impl FilterState {
fn new() -> Self { fn new() -> Self {
Self { Self {
suppression_mode: false, state: State::Streaming,
potential_json_mode: false,
brace_depth: 0,
buffer: String::new(), buffer: String::new(),
json_start_in_buffer: None, brace_depth: 0,
content_returned_up_to: 0, in_string: false,
potential_json_start: None, escape_next: false,
at_line_start: true, // Start of input counts as line start
pending_whitespace: String::new(),
} }
} }
fn reset(&mut self) { fn reset(&mut self) {
self.suppression_mode = false; self.state = State::Streaming;
self.potential_json_mode = false;
self.brace_depth = 0;
self.buffer.clear(); self.buffer.clear();
self.json_start_in_buffer = None; self.brace_depth = 0;
self.content_returned_up_to = 0; self.in_string = false;
self.potential_json_start = None; self.escape_next = false;
self.at_line_start = true;
self.pending_whitespace.clear();
} }
} }
/// Check if buffer matches the tool call pattern.
/// Pattern: `{` followed by optional whitespace, `"tool"`, optional whitespace, `:`, optional whitespace, `"`
///
/// Returns:
/// - Some(true) if confirmed as tool call
/// - Some(false) if confirmed NOT a tool call
/// - None if need more data
fn check_tool_pattern(buffer: &str) -> Option<bool> {
// Must start with {
if !buffer.starts_with('{') {
return Some(false);
}
let after_brace = &buffer[1..];
// Skip leading whitespace after {
let trimmed = after_brace.trim_start();
// Need at least `"tool":"` = 8 chars after whitespace
if trimmed.len() < 8 {
// Not enough data yet - but check for early rejection
if trimmed.starts_with('"') {
let after_quote = &trimmed[1..];
// If we have chars after the quote, check if it starts with 't'
if !after_quote.is_empty() && !after_quote.starts_with('t') {
return Some(false); // Definitely not "tool
}
if after_quote.len() >= 2 && !after_quote.starts_with("to") {
return Some(false);
}
if after_quote.len() >= 3 && !after_quote.starts_with("too") {
return Some(false);
}
if after_quote.len() >= 4 && !after_quote.starts_with("tool") {
return Some(false);
}
} else if !trimmed.is_empty() && !trimmed.starts_with('"') {
// First non-whitespace char after { is not " - not a tool call
return Some(false);
}
return None; // Need more data
}
// We have enough data - check the full pattern
// Must be: "tool" followed by optional whitespace, :, optional whitespace, "
if !trimmed.starts_with("\"tool\"") {
return Some(false);
}
let after_tool = trimmed[6..].trim_start(); // 6 = len of "tool"
if after_tool.is_empty() {
return None; // Need more data
}
if !after_tool.starts_with(':') {
return Some(false);
}
let after_colon = after_tool[1..].trim_start();
if after_colon.is_empty() {
return None; // Need more data
}
if after_colon.starts_with('"') {
return Some(true); // Confirmed tool call!
}
Some(false) // Has : but not followed by "
}
/// Filters JSON tool calls from streaming LLM content. /// Filters JSON tool calls from streaming LLM content.
/// ///
/// Processes content chunks and removes JSON tool calls while preserving regular text. /// Processes content character-by-character and removes JSON tool calls
/// Maintains state across calls to handle tool calls spanning multiple chunks. /// while preserving regular text. Maintains state across calls.
/// ///
/// # Arguments /// # Arguments
/// * `content` - A chunk of streaming content from the LLM /// * `content` - A chunk of streaming content from the LLM
@@ -86,383 +168,165 @@ pub fn filter_json_tool_calls(content: &str) -> String {
JSON_TOOL_STATE.with(|state| { JSON_TOOL_STATE.with(|state| {
let mut state = state.borrow_mut(); let mut state = state.borrow_mut();
let mut output = String::new();
// Add new content to buffer
state.buffer.push_str(content);
// If we're already in suppression mode, continue brace counting
if state.suppression_mode {
// Count braces in the new content only
for ch in content.chars() { for ch in content.chars() {
match ch { match state.state {
'{' => state.brace_depth += 1, State::Streaming => {
'}' => { handle_streaming_char(&mut state, ch, &mut output);
state.brace_depth -= 1;
// Exit suppression mode when all braces are closed
if state.brace_depth <= 0 {
debug!("JSON tool call completed - exiting suppression mode");
// Extract the complete result with JSON filtered out
let result = extract_content_without_json(
&state.buffer,
state.json_start_in_buffer.unwrap_or(0),
);
// Return only the part we haven't returned yet
let new_content = if result.len() > state.content_returned_up_to {
result[state.content_returned_up_to..].to_string()
} else {
String::new()
};
state.reset();
return new_content;
} }
State::Buffering => {
handle_buffering_char(&mut state, ch, &mut output);
}
State::Suppressing => {
handle_suppressing_char(&mut state, ch, &mut output);
} }
_ => {}
} }
} }
// After counting braces, if still in suppression mode, output
// check if a new tool call pattern appears. This handles truncated JSON
// followed by complete JSON.
if state.suppression_mode {
let current_json_start = state.json_start_in_buffer.unwrap();
// Don't require newline - the new JSON might be concatenated directly
let tool_call_regex = Regex::new(r#"\{\s*"tool"\s*:\s*""#).unwrap();
// Look for new tool call patterns after the current one
if let Some(captures) = tool_call_regex.find(&state.buffer[current_json_start + 1..]) {
let new_json_start = current_json_start + 1 + captures.start() + captures.as_str().find('{').unwrap();
debug!("Detected new tool call at position {} while processing incomplete one at {} - discarding old", new_json_start, current_json_start);
// The previous JSON was incomplete/malformed
// Return content before the old JSON (if any)
let content_before_old_json = if current_json_start > state.content_returned_up_to {
state.buffer[state.content_returned_up_to..current_json_start].to_string()
} else {
String::new()
};
// Update state to skip the incomplete JSON and position at the new one
// We'll process the new JSON on the next call
state.content_returned_up_to = new_json_start;
state.suppression_mode = false;
state.json_start_in_buffer = None;
state.brace_depth = 0;
return content_before_old_json;
}
}
// Still in suppression mode, return empty string (content is being accumulated)
return String::new();
}
// Check if we're in potential JSON mode (saw { but waiting to confirm it's a tool call)
if state.potential_json_mode {
// Check if the buffer contains a confirmed tool call pattern
let tool_call_regex = Regex::new(r#"(?m)^\s*\{\s*"tool"\s*:\s*""#).unwrap();
if let Some(captures) = tool_call_regex.find(&state.buffer) {
// Confirmed! This is a tool call - enter suppression mode
let match_text = captures.as_str();
if let Some(brace_offset) = match_text.find('{') {
let json_start = captures.start() + brace_offset;
debug!("Confirmed JSON tool call at position {} - entering suppression mode", json_start);
state.potential_json_mode = false;
state.suppression_mode = true;
state.brace_depth = 0;
state.json_start_in_buffer = Some(json_start);
// Count braces from json_start to see if JSON is complete
let buffer_slice = state.buffer[json_start..].to_string();
for ch in buffer_slice.chars() {
match ch {
'{' => state.brace_depth += 1,
'}' => {
state.brace_depth -= 1;
if state.brace_depth <= 0 {
debug!("JSON tool call completed immediately");
let result = extract_content_without_json(&state.buffer, json_start);
let new_content = if result.len() > state.content_returned_up_to {
result[state.content_returned_up_to..].to_string()
} else {
String::new()
};
state.reset();
return new_content;
}
}
_ => {}
}
}
// JSON incomplete, stay in suppression mode, return nothing
return String::new();
}
}
// Check if we can rule out this being a tool call
// If we have enough content after the { and it doesn't match the pattern, release it
if let Some(potential_start) = state.potential_json_start {
let content_after_brace = &state.buffer[potential_start..];
// Rule out as a tool call if:
// 1. Closing } appears before we see the full pattern
// 2. Content clearly doesn't match the tool call pattern
// 3. Newline appears after the opening brace (tool calls should be compact)
let has_closing_brace = content_after_brace.contains('}');
let has_newline = content_after_brace[1..].contains('\n'); // Skip first char which is {
let long_enough = content_after_brace.len() >= 10;
// Detect non-tool JSON patterns:
// - { followed by " and a key that doesn't start with "tool"
// - { followed by "t" but not "to"
// - { followed by "to" but not "too", etc.
let not_tool_pattern = Regex::new(r#"^\{\s*"(?:[^t]|t(?:[^o]|o(?:[^o]|o(?:[^l]|l[^"\s:]))))"#).unwrap();
let definitely_not_tool = not_tool_pattern.is_match(content_after_brace);
if has_closing_brace || has_newline || (long_enough && definitely_not_tool) {
debug!("Potential JSON ruled out - not a tool call");
state.potential_json_mode = false;
state.potential_json_start = None;
// Return the buffered content we've been holding
let new_content = if state.buffer.len() > state.content_returned_up_to {
state.buffer[state.content_returned_up_to..].to_string()
} else {
String::new()
};
state.content_returned_up_to = state.buffer.len();
return new_content;
}
}
// Still in potential mode, keep buffering
return String::new();
}
// Detect potential JSON start: { at the beginning of a line
let potential_json_regex = Regex::new(r"(?m)^\s*\{\s*").unwrap();
if let Some(captures) = potential_json_regex.find(&state.buffer[state.content_returned_up_to..]) {
let match_start = state.content_returned_up_to + captures.start();
let brace_pos = match_start + captures.as_str().find('{').unwrap();
debug!("Potential JSON detected at position {} - entering buffering mode", brace_pos);
// Fast path: check if this is already a confirmed tool call
let tool_call_regex = Regex::new(r#"(?m)^\s*\{\s*"tool"\s*:\s*""#).unwrap();
if tool_call_regex.is_match(&state.buffer[brace_pos..]) {
// This is a confirmed tool call! Process it immediately
let json_start = brace_pos;
debug!("Immediately confirmed tool call at position {}", json_start);
// Return content before JSON
let content_before = if json_start > state.content_returned_up_to {
state.buffer[state.content_returned_up_to..json_start].to_string()
} else {
String::new()
};
state.content_returned_up_to = json_start;
state.suppression_mode = true;
state.brace_depth = 0;
state.json_start_in_buffer = Some(json_start);
// Count braces to see if JSON is complete
let buffer_slice = state.buffer[json_start..].to_string();
for ch in buffer_slice.chars() {
match ch {
'{' => state.brace_depth += 1,
'}' => {
state.brace_depth -= 1;
if state.brace_depth <= 0 {
debug!("JSON tool call completed in same chunk");
let result = extract_content_without_json(&state.buffer, json_start);
let content_after = if result.len() > json_start {
&result[json_start..]
} else {
""
};
let final_result = format!("{}{}", content_before, content_after);
state.reset();
return final_result;
}
}
_ => {}
}
}
// JSON incomplete, return content before and stay in suppression mode
return content_before;
}
// Return content before the potential JSON
let content_before = if brace_pos > state.content_returned_up_to {
state.buffer[state.content_returned_up_to..brace_pos].to_string()
} else {
String::new()
};
state.content_returned_up_to = brace_pos;
state.potential_json_mode = true;
state.potential_json_start = Some(brace_pos);
// Optimization: immediately check if we can rule this out for single-chunk processing
let content_after_brace = &state.buffer[brace_pos..];
let has_closing_brace = content_after_brace.contains('}');
let has_newline = content_after_brace.len() > 1 && content_after_brace[1..].contains('\n');
let long_enough = content_after_brace.len() >= 10;
let not_tool_pattern = Regex::new(r#"^\{\s*"(?:[^t]|t(?:[^o]|o(?:[^o]|o(?:[^l]|l[^"\s:]))))"#).unwrap();
let definitely_not_tool = not_tool_pattern.is_match(content_after_brace);
if has_closing_brace || has_newline || (long_enough && definitely_not_tool) {
debug!("Immediately ruled out as not a tool call");
state.potential_json_mode = false;
state.potential_json_start = None;
// Return all the buffered content
let new_content = if state.buffer.len() > state.content_returned_up_to {
state.buffer[state.content_returned_up_to..].to_string()
} else {
String::new()
};
state.content_returned_up_to = state.buffer.len();
return format!("{}{}", content_before, new_content);
}
return content_before;
}
// Check for tool call pattern using corrected regex
let tool_call_regex = Regex::new(r#"(?m)^\s*\{\s*"tool"\s*:\s*"[^"]*""#).unwrap();
if let Some(captures) = tool_call_regex.find(&state.buffer) {
let match_text = captures.as_str();
// Find the position of the opening brace in the match
if let Some(brace_offset) = match_text.find('{') {
let json_start = captures.start() + brace_offset;
debug!(
"Detected JSON tool call at position {} - entering suppression mode",
json_start
);
// Return content before JSON that we haven't returned yet
let content_before_json = if json_start >= state.content_returned_up_to {
state.buffer[state.content_returned_up_to..json_start].to_string()
} else {
String::new()
};
state.content_returned_up_to = json_start;
// Enter suppression mode
state.suppression_mode = true;
state.brace_depth = 0;
state.json_start_in_buffer = Some(json_start);
// Count braces from the JSON start to see if it's complete
let buffer_clone = state.buffer.clone();
for ch in buffer_clone[json_start..].chars() {
match ch {
'{' => state.brace_depth += 1,
'}' => {
state.brace_depth -= 1;
if state.brace_depth <= 0 {
// JSON is complete in this chunk
debug!("JSON tool call completed in same chunk");
let result = extract_content_without_json(&buffer_clone, json_start);
// Return content before JSON plus content after JSON
let content_after_json = if result.len() > json_start {
&result[json_start..]
} else {
""
};
let final_result =
format!("{}{}", content_before_json, content_after_json);
state.reset();
return final_result;
}
}
_ => {}
}
}
// JSON is incomplete, return only the content before JSON
return content_before_json;
}
}
// No JSON tool call detected, return only the new content we haven't returned yet
if state.buffer.len() > state.content_returned_up_to {
let result = state.buffer[state.content_returned_up_to..].to_string();
state.content_returned_up_to = state.buffer.len();
result
} else {
String::new()
}
}) })
} }
/// Extracts content from buffer, removing the JSON tool call. /// Handle a character in Streaming state
/// fn handle_streaming_char(state: &mut FilterState, ch: char, output: &mut String) {
/// Given a buffer and the start position of a JSON tool call, this function: match ch {
/// 1. Extracts all content before the JSON '\n' => {
/// 2. Finds the end of the JSON (matching closing brace) // Output the newline and any pending whitespace
/// 3. Extracts all content after the JSON output.push_str(&state.pending_whitespace);
/// 4. Returns the concatenation of before + after (JSON removed) output.push(ch);
/// state.pending_whitespace.clear();
/// # Arguments state.at_line_start = true;
/// * `full_content` - The full content buffer }
/// * `json_start` - Position where the JSON tool call begins ' ' | '\t' if state.at_line_start => {
fn extract_content_without_json(full_content: &str, json_start: usize) -> String { // Accumulate whitespace at line start
// Find the end of the JSON using proper brace counting with string handling state.pending_whitespace.push(ch);
let mut brace_depth = 0; }
let mut json_end = json_start; '{' if state.at_line_start => {
let mut in_string = false; // Potential tool call! Enter buffering mode
let mut escape_next = false; debug!("Potential tool call detected - entering Buffering state");
state.state = State::Buffering;
state.buffer.clear();
state.buffer.push(ch);
// Don't output pending_whitespace yet - we might need to suppress it
}
_ => {
// Regular character - output any pending whitespace first
output.push_str(&state.pending_whitespace);
state.pending_whitespace.clear();
output.push(ch);
state.at_line_start = false;
}
}
}
for (i, ch) in full_content[json_start..].char_indices() { /// Handle a character in Buffering state
if escape_next { fn handle_buffering_char(state: &mut FilterState, ch: char, output: &mut String) {
escape_next = false; state.buffer.push(ch);
continue;
// Check if we can determine tool call status
match check_tool_pattern(&state.buffer) {
Some(true) => {
// Confirmed tool call! Enter suppression mode
debug!("Confirmed tool call - entering Suppressing state");
state.state = State::Suppressing;
state.brace_depth = 1; // We already have the opening {
state.in_string = true; // We're inside the "tool" value string
state.escape_next = false;
// Discard pending_whitespace (it's part of the tool call line)
state.pending_whitespace.clear();
state.buffer.clear();
}
Some(false) => {
// Not a tool call - release buffered content
debug!("Not a tool call - releasing buffer");
output.push_str(&state.pending_whitespace);
output.push_str(&state.buffer);
state.pending_whitespace.clear();
state.buffer.clear();
state.state = State::Streaming;
state.at_line_start = ch == '\n';
}
None => {
// Need more data - check if buffer is getting too long
if state.buffer.len() > MAX_BUFFER_FOR_DETECTION {
// Too long without confirmation - not a tool call
debug!("Buffer exceeded max length - not a tool call");
output.push_str(&state.pending_whitespace);
output.push_str(&state.buffer);
state.pending_whitespace.clear();
state.buffer.clear();
state.state = State::Streaming;
state.at_line_start = false;
}
// Otherwise keep buffering
}
}
}
/// Handle a character in Suppressing state (string-aware brace counting)
fn handle_suppressing_char(state: &mut FilterState, ch: char, _output: &mut String) {
// Track chars to detect if we see a new tool call pattern while suppressing
// This handles truncated JSON followed by complete JSON
state.buffer.push(ch);
// Handle escape sequences
if state.escape_next {
state.escape_next = false;
return;
} }
match ch { match ch {
'\\' if in_string => escape_next = true, '\\' if state.in_string => {
'"' if !escape_next => in_string = !in_string, state.escape_next = true;
'{' if !in_string => {
brace_depth += 1;
} }
'}' if !in_string => { '"' => {
brace_depth -= 1; state.in_string = !state.in_string;
if brace_depth == 0 { }
json_end = json_start + i + 1; // +1 to include the closing brace '{' if !state.in_string => {
break; state.brace_depth += 1;
}
'}' if !state.in_string => {
state.brace_depth -= 1;
if state.brace_depth <= 0 {
// JSON complete! Return to streaming
debug!("Tool call complete - returning to Streaming state");
state.state = State::Streaming;
state.at_line_start = false; // We're right after the }
state.in_string = false;
state.escape_next = false;
state.buffer.clear();
} }
} }
_ => {} _ => {}
} }
// Check if we're seeing a new tool call pattern (truncated JSON case)
// This can happen with or without a newline before the new {
// Look for { followed by tool pattern in the buffer
if state.buffer.len() >= 10 {
// Find the last { that could start a new tool call
for (i, c) in state.buffer.char_indices().rev() {
if c == '{' && i > 0 {
let potential_tool = &state.buffer[i..];
if let Some(true) = check_tool_pattern(potential_tool) {
// New tool call detected! Restart suppression from here
debug!("New tool call detected while suppressing - restarting");
state.brace_depth = 1;
state.in_string = true;
// Keep only the part after the new { for continued tracking
state.buffer = potential_tool.to_string();
return;
}
}
} }
// Return content before and after the JSON (excluding the JSON itself) // Limit buffer size to prevent unbounded growth
let before = &full_content[..json_start]; if state.buffer.len() > 200 {
let after = if json_end < full_content.len() { let keep_from = state.buffer.len() - 100;
&full_content[json_end..] state.buffer = state.buffer[keep_from..].to_string();
} else { }
"" }
};
format!("{}{}", before, after)
} }
/// Resets the global JSON filtering state. /// Resets the global JSON filtering state.
@@ -475,3 +339,78 @@ pub fn reset_json_tool_state() {
state.reset(); state.reset();
}); });
} }
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_check_tool_pattern_confirmed() {
assert_eq!(check_tool_pattern(r#"{"tool":""
"#), Some(true));
assert_eq!(check_tool_pattern(r#"{"tool": "shell""#), Some(true));
assert_eq!(check_tool_pattern(r#"{ "tool" : "test""#), Some(true));
}
#[test]
fn test_check_tool_pattern_rejected() {
assert_eq!(check_tool_pattern(r#"{"other": "value"}"#), Some(false));
assert_eq!(check_tool_pattern(r#"{"tools": "value"}"#), Some(false));
assert_eq!(check_tool_pattern(r#"{"tool": 123}"#), Some(false)); // number not string
}
#[test]
fn test_check_tool_pattern_need_more() {
assert_eq!(check_tool_pattern(r#"{"#), None);
assert_eq!(check_tool_pattern(r#"{"tool"#), None);
assert_eq!(check_tool_pattern(r#"{"tool":"#), None);
}
#[test]
fn test_passthrough_no_tool() {
reset_json_tool_state();
let input = "Hello world";
assert_eq!(filter_json_tool_calls(input), input);
}
#[test]
fn test_simple_tool_filtered() {
reset_json_tool_state();
let input = "Before\n{\"tool\": \"shell\", \"args\": {}}\nAfter";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Before\n\nAfter");
}
#[test]
fn test_tool_with_braces_in_string() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\", \"args\": {\"cmd\": \"echo }\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_non_tool_json_passes_through() {
reset_json_tool_state();
let input = "Text\n{\"other\": \"value\"}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, input);
}
#[test]
fn test_streaming_chunks() {
reset_json_tool_state();
let chunks = vec![
"Before\n",
"{\"tool\": \"",
"shell\", \"args\": {}",
"}\nAfter",
];
let mut result = String::new();
for chunk in chunks {
result.push_str(&filter_json_tool_calls(chunk));
}
assert_eq!(result, "Before\n\nAfter");
}
}

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@@ -0,0 +1,639 @@
//! Stress tests for JSON tool call filtering.
//!
//! These tests hammer the filter with malformed JSON, partial tool calls,
//! edge cases, and adversarial inputs to ensure robustness.
use g3_cli::filter_json::{filter_json_tool_calls, reset_json_tool_state};
// ============================================================================
// Malformed JSON Tests
// ============================================================================
#[test]
fn test_unclosed_brace_at_end() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\", \"args\": {\"cmd\": \"ls\"";
let result = filter_json_tool_calls(input);
// Should suppress the incomplete tool call
assert_eq!(result, "Text\n");
}
#[test]
fn test_missing_closing_quote() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\", \"args\": {\"cmd\": \"ls}}\nMore";
let result = filter_json_tool_calls(input);
// The unbalanced quote makes brace counting tricky
// Should still filter the tool call attempt
assert_eq!(result, "Text\n");
}
#[test]
fn test_extra_closing_braces() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\", \"args\": {}}}}}\nMore";
let result = filter_json_tool_calls(input);
// Extra braces after valid JSON should pass through
assert_eq!(result, "Text\n}}}\nMore");
}
#[test]
fn test_deeply_nested_malformed() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"x\", \"args\": {{{{{{}}}}}}}\nMore";
let result = filter_json_tool_calls(input);
// Should handle deep nesting - extra braces get consumed as part of the tool call
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_null_bytes_in_json() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\0\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
// Should handle null bytes gracefully
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_unicode_in_tool_name() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shëll\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
// Unicode in tool name - still a valid tool call pattern
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_emoji_in_args() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\", \"args\": {\"msg\": \"Hello 🎉\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_very_long_string_value() {
reset_json_tool_state();
let long_string = "x".repeat(10000);
let input = format!("Text\n{{\"tool\": \"shell\", \"args\": {{\"data\": \"{}\"}}}}\nMore", long_string);
let result = filter_json_tool_calls(&input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_many_escaped_quotes() {
reset_json_tool_state();
let input = r#"Text
{"tool": "shell", "args": {"cmd": "echo \"a\" \"b\" \"c\" \"d\" \"e\""}}
More"#;
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_escaped_backslash_before_quote() {
reset_json_tool_state();
// This is: {"tool": "shell", "args": {"path": "C:\\"}}
let input = "Text\n{\"tool\": \"shell\", \"args\": {\"path\": \"C:\\\\\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_newlines_inside_string() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"shell\", \"args\": {\"cmd\": \"echo\\nworld\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
// ============================================================================
// Partial Tool Call Pattern Tests
// ============================================================================
#[test]
fn test_just_opening_brace() {
reset_json_tool_state();
let result = filter_json_tool_calls("Text\n{");
// Should buffer, waiting for more
assert_eq!(result, "Text\n");
// Now send something that's not a tool call
let result2 = filter_json_tool_calls("\"other\": 1}\nMore");
assert_eq!(result2, "{\"other\": 1}\nMore");
}
#[test]
fn test_partial_tool_keyword() {
reset_json_tool_state();
let chunks = vec!["Text\n{", "\"to", "ol", "\": ", "\"sh", "ell\"", ", \"args\": {}", "}\nMore"];
let mut result = String::new();
for chunk in chunks {
result.push_str(&filter_json_tool_calls(chunk));
}
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_tool_then_not_colon() {
reset_json_tool_state();
let input = "Text\n{\"tool\" \"shell\"}\nMore"; // Missing colon
let result = filter_json_tool_calls(input);
// Not a valid tool call pattern - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tool_colon_then_number() {
reset_json_tool_state();
let input = "Text\n{\"tool\": 123}\nMore"; // Number instead of string
let result = filter_json_tool_calls(input);
// Not a valid tool call pattern - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tool_colon_then_null() {
reset_json_tool_state();
let input = "Text\n{\"tool\": null}\nMore";
let result = filter_json_tool_calls(input);
// Not a valid tool call pattern - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tool_colon_then_array() {
reset_json_tool_state();
let input = "Text\n{\"tool\": []}\nMore";
let result = filter_json_tool_calls(input);
// Not a valid tool call pattern - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tool_colon_then_object() {
reset_json_tool_state();
let input = "Text\n{\"tool\": {}}\nMore";
let result = filter_json_tool_calls(input);
// Not a valid tool call pattern - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tools_plural() {
reset_json_tool_state();
let input = "Text\n{\"tools\": \"shell\"}\nMore";
let result = filter_json_tool_calls(input);
// "tools" is not "tool" - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tool_with_prefix() {
reset_json_tool_state();
let input = "Text\n{\"mytool\": \"shell\"}\nMore";
let result = filter_json_tool_calls(input);
// "mytool" is not "tool" - should pass through
assert_eq!(result, input);
}
#[test]
fn test_tool_uppercase() {
reset_json_tool_state();
let input = "Text\n{\"TOOL\": \"shell\"}\nMore";
let result = filter_json_tool_calls(input);
// "TOOL" is not "tool" - should pass through
assert_eq!(result, input);
}
// ============================================================================
// Streaming Edge Cases
// ============================================================================
#[test]
fn test_single_char_streaming() {
reset_json_tool_state();
let input = "Hi\n{\"tool\": \"x\", \"args\": {}}\nBye";
let mut result = String::new();
for ch in input.chars() {
result.push_str(&filter_json_tool_calls(&ch.to_string()));
}
assert_eq!(result, "Hi\n\nBye");
}
#[test]
fn test_two_char_streaming() {
reset_json_tool_state();
let input = "Hi\n{\"tool\": \"x\", \"args\": {}}\nBye";
let mut result = String::new();
let chars: Vec<char> = input.chars().collect();
for chunk in chars.chunks(2) {
let s: String = chunk.iter().collect();
result.push_str(&filter_json_tool_calls(&s));
}
assert_eq!(result, "Hi\n\nBye");
}
#[test]
fn test_random_chunk_sizes() {
reset_json_tool_state();
let input = "Before\n{\"tool\": \"shell\", \"args\": {\"cmd\": \"ls -la\"}}\nAfter";
// Chunk at various sizes
let chunk_sizes = [1, 3, 7, 11, 13, 17];
for &size in &chunk_sizes {
reset_json_tool_state();
let mut result = String::new();
let mut pos = 0;
while pos < input.len() {
let end = (pos + size).min(input.len());
let chunk = &input[pos..end];
result.push_str(&filter_json_tool_calls(chunk));
pos = end;
}
assert_eq!(result, "Before\n\nAfter", "Failed with chunk size {}", size);
}
}
#[test]
fn test_chunk_boundary_at_brace() {
reset_json_tool_state();
let chunks = vec!["Text\n", "{", "\"tool\": \"x\", \"args\": {}", "}", "\nMore"];
let mut result = String::new();
for chunk in chunks {
result.push_str(&filter_json_tool_calls(chunk));
}
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_chunk_boundary_at_quote() {
reset_json_tool_state();
let chunks = vec!["Text\n{\"tool\": \"", "shell", "\", \"args\": {}}", "\nMore"];
let mut result = String::new();
for chunk in chunks {
result.push_str(&filter_json_tool_calls(chunk));
}
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_chunk_boundary_at_colon() {
reset_json_tool_state();
let chunks = vec!["Text\n{\"tool\"", ":", " \"shell\", \"args\": {}}\nMore"];
let mut result = String::new();
for chunk in chunks {
result.push_str(&filter_json_tool_calls(chunk));
}
assert_eq!(result, "Text\n\nMore");
}
// ============================================================================
// Multiple Tool Calls
// ============================================================================
#[test]
fn test_two_tool_calls_same_line() {
reset_json_tool_state();
// Two tool calls on same line (no newline between)
let input = "Text\n{\"tool\": \"a\", \"args\": {}}{\"tool\": \"b\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
// First is filtered (starts at line beginning)
// Second starts immediately after first's }, not at line start, so passes through
// This is acceptable - LLMs typically put tool calls on separate lines
assert_eq!(result, "Text\n{\"tool\": \"b\", \"args\": {}}\nMore");
}
#[test]
fn test_three_tool_calls_separate_lines() {
reset_json_tool_state();
let input = "A\n{\"tool\": \"x\", \"args\": {}}\nB\n{\"tool\": \"y\", \"args\": {}}\nC\n{\"tool\": \"z\", \"args\": {}}\nD";
let result = filter_json_tool_calls(input);
assert_eq!(result, "A\n\nB\n\nC\n\nD");
}
#[test]
fn test_tool_call_then_regular_json() {
reset_json_tool_state();
let input = "A\n{\"tool\": \"x\", \"args\": {}}\nB\n{\"data\": 123}\nC";
let result = filter_json_tool_calls(input);
// First is tool call (filtered), second is regular JSON (kept)
assert_eq!(result, "A\n\nB\n{\"data\": 123}\nC");
}
#[test]
fn test_regular_json_then_tool_call() {
reset_json_tool_state();
let input = "A\n{\"data\": 123}\nB\n{\"tool\": \"x\", \"args\": {}}\nC";
let result = filter_json_tool_calls(input);
assert_eq!(result, "A\n{\"data\": 123}\nB\n\nC");
}
// ============================================================================
// Adversarial Inputs
// ============================================================================
#[test]
fn test_fake_tool_in_string() {
reset_json_tool_state();
// The tool pattern appears inside a string value
let input = r#"Text
{"message": "{\"tool\": \"shell\"}"}
More"#;
let result = filter_json_tool_calls(input);
// Should pass through - the pattern is inside a string
assert_eq!(result, input);
}
#[test]
fn test_nested_json_with_tool_key() {
reset_json_tool_state();
// Nested object has "tool" key but outer doesn't match pattern
let input = "Text\n{\"outer\": {\"tool\": \"inner\"}}\nMore";
let result = filter_json_tool_calls(input);
// Should pass through - outer object doesn't start with "tool"
assert_eq!(result, input);
}
#[test]
fn test_brace_bomb() {
reset_json_tool_state();
// Many braces to stress the counter
let input = "Text\n{\"tool\": \"x\", \"args\": {\"a\": {\"b\": {\"c\": {\"d\": {\"e\": {}}}}}}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_string_with_many_braces() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"x\", \"args\": {\"code\": \"{{{{}}}}\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_alternating_braces_in_string() {
reset_json_tool_state();
let input = "Text\n{\"tool\": \"x\", \"args\": {\"pat\": \"}{}{}{\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_quote_after_backslash_in_string() {
reset_json_tool_state();
// Tricky: \" inside string should not end the string
let input = r#"Text
{"tool": "x", "args": {"msg": "say \"hi\""}}
More"#;
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_double_backslash_then_quote() {
reset_json_tool_state();
// \\ followed by " - the quote DOES end the string
let input = "Text\n{\"tool\": \"x\", \"args\": {\"path\": \"C:\\\\\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_triple_backslash_then_quote() {
reset_json_tool_state();
// \\\" - escaped backslash followed by escaped quote
let input = "Text\n{\"tool\": \"x\", \"args\": {\"s\": \"a\\\\\\\"b\"}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
// ============================================================================
// Whitespace Variations
// ============================================================================
#[test]
fn test_tabs_before_brace() {
reset_json_tool_state();
let input = "Text\n\t\t{\"tool\": \"x\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_spaces_before_brace() {
reset_json_tool_state();
let input = "Text\n {\"tool\": \"x\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_mixed_whitespace_before_brace() {
reset_json_tool_state();
let input = "Text\n \t \t {\"tool\": \"x\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_space_after_opening_brace() {
reset_json_tool_state();
let input = "Text\n{ \"tool\": \"x\", \"args\": {}}\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_lots_of_space_in_json() {
reset_json_tool_state();
let input = "Text\n{ \"tool\" : \"x\" , \"args\" : { } }\nMore";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Text\n\nMore");
}
#[test]
fn test_crlf_line_endings() {
reset_json_tool_state();
let input = "Text\r\n{\"tool\": \"x\", \"args\": {}}\r\nMore";
let result = filter_json_tool_calls(input);
// \r is not treated as line start, so { after \r\n should work
// Actually \n triggers line start, \r is just a regular char
assert_eq!(result, "Text\r\n\r\nMore");
}
// ============================================================================
// Empty and Minimal Cases
// ============================================================================
#[test]
fn test_empty_input() {
reset_json_tool_state();
assert_eq!(filter_json_tool_calls(""), "");
}
#[test]
fn test_just_newline() {
reset_json_tool_state();
assert_eq!(filter_json_tool_calls("\n"), "\n");
}
#[test]
fn test_just_brace() {
reset_json_tool_state();
let r1 = filter_json_tool_calls("{");
// At start of input (line start), { triggers buffering
assert_eq!(r1, "");
// Send non-tool content - the newline comes through
let r2 = filter_json_tool_calls("}\n");
assert_eq!(r2, "{}\n");
}
#[test]
fn test_minimal_tool_call() {
reset_json_tool_state();
let input = "{\"tool\":\"x\",\"args\":{}}";
let result = filter_json_tool_calls(input);
assert_eq!(result, "");
}
#[test]
fn test_tool_call_at_very_start() {
reset_json_tool_state();
let input = "{\"tool\": \"x\", \"args\": {}}\nAfter";
let result = filter_json_tool_calls(input);
assert_eq!(result, "\nAfter");
}
// ============================================================================
// State Reset Tests
// ============================================================================
#[test]
fn test_reset_clears_buffering_state() {
reset_json_tool_state();
// Start a potential tool call
let _ = filter_json_tool_calls("Text\n{");
// Reset
reset_json_tool_state();
// New input should work fresh
let result = filter_json_tool_calls("Fresh start");
assert_eq!(result, "Fresh start");
}
#[test]
fn test_reset_clears_suppressing_state() {
reset_json_tool_state();
// Start suppressing a tool call
let _ = filter_json_tool_calls("Text\n{\"tool\": \"x\", \"args\": {");
// Reset
reset_json_tool_state();
// New input should work fresh
let result = filter_json_tool_calls("Fresh start");
assert_eq!(result, "Fresh start");
}
// ============================================================================
// Real-World Patterns from Bug Reports
// ============================================================================
#[test]
fn test_str_replace_with_diff() {
reset_json_tool_state();
let input = r#"I'll update the file:
{"tool": "str_replace", "args": {"file_path": "src/main.rs", "diff": "@@ -1,3 +1,4 @@\n fn main() {\n+ println!(\"Hello\");\n }"}}
Done!"#;
let result = filter_json_tool_calls(input);
assert_eq!(result, "I'll update the file:\n\nDone!");
}
#[test]
fn test_shell_with_complex_command() {
reset_json_tool_state();
let input = r#"Running command:
{"tool": "shell", "args": {"command": "find . -name '*.rs' -exec grep -l 'TODO' {} \;"}}
Results above."#;
let result = filter_json_tool_calls(input);
assert_eq!(result, "Running command:\n\nResults above.");
}
#[test]
fn test_write_file_with_json_content() {
reset_json_tool_state();
let input = r#"Creating config:
{"tool": "write_file", "args": {"file_path": "config.json", "content": "{\"key\": \"value\"}"}}
File created."#;
let result = filter_json_tool_calls(input);
assert_eq!(result, "Creating config:\n\nFile created.");
}
#[test]
fn test_read_file_simple() {
reset_json_tool_state();
let input = "Let me check:\n{\"tool\": \"read_file\", \"args\": {\"file_path\": \"README.md\"}}\nHere's what I found:";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Let me check:\n\nHere's what I found:");
}
#[test]
fn test_final_output() {
reset_json_tool_state();
let input = "Task complete.\n{\"tool\": \"final_output\", \"args\": {\"summary\": \"# Summary\\n\\nI completed the task.\\n\\n## Details\\n- Item 1\\n- Item 2\"}}\n";
let result = filter_json_tool_calls(input);
assert_eq!(result, "Task complete.\n\n");
}
// ============================================================================
// Truncated JSON followed by Complete JSON (the original bug)
// ============================================================================
#[test]
fn test_truncated_then_complete_streaming() {
reset_json_tool_state();
// Chunk 1: text
let r1 = filter_json_tool_calls("Some text\n");
assert_eq!(r1, "Some text\n");
// Chunk 2: truncated tool call
let r2 = filter_json_tool_calls(r#"{"tool": "str_replace", "args": {"diff":"partial"#);
assert_eq!(r2, "");
// Chunk 3: new complete tool call (LLM retry)
let r3 = filter_json_tool_calls(r#"{"tool": "str_replace", "args": {"diff":"complete", "file_path":"x.rs"}}"#);
assert_eq!(r3, "");
// Chunk 4: text after
let r4 = filter_json_tool_calls("\nMore text");
assert_eq!(r4, "\nMore text");
}
#[test]
fn test_multiple_truncated_then_complete() {
reset_json_tool_state();
let chunks = vec![
"Start\n",
r#"{"tool": "a", "args": {"x": "trunc"#, // truncated
r#"{"tool": "b", "args": {"y": "also_trunc"#, // another truncated
r#"{"tool": "c", "args": {"z": "complete"}}"#, // finally complete
"\nEnd",
];
let mut result = String::new();
for chunk in chunks {
result.push_str(&filter_json_tool_calls(chunk));
}
assert_eq!(result, "Start\n\nEnd");
}