normalize_native_rules/

high_complexity.rs

//! `high-complexity` native rule — flags functions exceeding a cyclomatic complexity threshold.
//!
//! Uses tree-sitter tags queries to identify functions and complexity queries
//! (or the `compute_complexity` fallback) to measure cyclomatic complexity.
//!
//! # Configuration
//!
//! The threshold is configurable via `.normalize/config.toml`:
//!
//! ```toml
//! [rules.rule."high-complexity"]
//! threshold = 10   # default: 20
//! ```

use normalize_facts::extract::compute_complexity;
use normalize_languages::parsers::{grammar_loader, parse_with_grammar};
use normalize_languages::support_for_path;
use normalize_output::diagnostics::{DiagnosticsReport, Issue, Severity};
use std::path::Path;
use streaming_iterator::StreamingIterator;

use crate::cache::{FileRule, run_file_rule};
use normalize_rules_config::WalkConfig;

/// Serializable per-file finding for the high-complexity rule.
#[derive(serde::Serialize, serde::Deserialize)]
pub struct HighComplexityFinding {
    rel_path: String,
    name: String,
    start_line: usize,
    complexity: usize,
}

/// Rule that flags functions exceeding a cyclomatic complexity threshold.
pub struct HighComplexityRule {
    pub threshold: usize,
}

impl FileRule for HighComplexityRule {
    type Finding = HighComplexityFinding;

    fn engine_name(&self) -> &str {
        "high-complexity"
    }

    fn config_hash(&self) -> String {
        self.threshold.to_string()
    }

    fn check_file(&self, path: &Path, root: &Path) -> Vec<Self::Finding> {
        let support = match support_for_path(path) {
            Some(s) => s,
            None => return Vec::new(),
        };
        let content = match std::fs::read_to_string(path) {
            Ok(c) => c,
            Err(_) => return Vec::new(),
        };

        let grammar_name = support.grammar_name();
        let tree = match parse_with_grammar(grammar_name, &content) {
            Some(t) => t,
            None => return Vec::new(),
        };

        let loader = grammar_loader();
        let tags_scm = match loader.get_tags(grammar_name) {
            Some(t) => t,
            None => return Vec::new(),
        };
        let ts_lang = match loader.get(grammar_name) {
            Ok(l) => l,
            Err(_) => return Vec::new(),
        };
        let tags_query = match tree_sitter::Query::new(&ts_lang, &tags_scm) {
            Ok(q) => q,
            Err(_) => return Vec::new(),
        };

        let complexity_query = loader.get_complexity(grammar_name).and_then(|scm| {
            let grammar = loader.get(grammar_name).ok()?;
            tree_sitter::Query::new(&grammar, &scm).ok()
        });

        let capture_names = tags_query.capture_names();
        let root_node = tree.root_node();
        let mut qcursor = tree_sitter::QueryCursor::new();
        let mut matches = qcursor.matches(&tags_query, root_node, content.as_bytes());

        let rel_path = path
            .strip_prefix(root)
            .unwrap_or(path)
            .to_string_lossy()
            .to_string();

        let mut results = Vec::new();

        while let Some(m) = matches.next() {
            for capture in m.captures {
                let cn = capture_names[capture.index as usize];
                if !matches!(cn, "definition.function" | "definition.method") {
                    continue;
                }

                let node = capture.node;
                let name = match support.node_name(&node, &content) {
                    Some(n) => n.to_string(),
                    None => continue,
                };

                let complexity = if let Some(ref cq) = complexity_query {
                    count_complexity_with_query(&node, cq, &content)
                } else {
                    compute_complexity(&node, support, content.as_bytes())
                };

                if complexity >= self.threshold {
                    let start_line = node.start_position().row + 1;
                    results.push(HighComplexityFinding {
                        rel_path: rel_path.clone(),
                        name,
                        start_line,
                        complexity,
                    });
                }
            }
        }

        results
    }

    fn to_diagnostics(
        &self,
        findings: Vec<(std::path::PathBuf, Vec<Self::Finding>)>,
        _root: &Path,
        files_checked: usize,
    ) -> DiagnosticsReport {
        let threshold = self.threshold;

        let mut issues: Vec<Issue> = findings
            .into_iter()
            .flat_map(|(_path, file_findings)| file_findings)
            .map(|f| Issue {
                file: f.rel_path,
                line: Some(f.start_line),
                column: None,
                end_line: None,
                end_column: None,
                rule_id: "high-complexity".into(),
                message: format!(
                    "function `{}` has cyclomatic complexity {} (threshold: {threshold})",
                    f.name, f.complexity
                ),
                severity: Severity::Warning,
                source: "high-complexity".into(),
                related: vec![],
                suggestion: Some(
                    "consider extracting helper functions to reduce complexity".into(),
                ),
            })
            .collect();

        // Sort by complexity descending.
        issues.sort_by(|a, b| {
            let extract = |msg: &str| -> usize {
                msg.rsplit("complexity ")
                    .next()
                    .and_then(|s| s.split(' ').next())
                    .and_then(|s| s.parse().ok())
                    .unwrap_or(0)
            };
            extract(&b.message).cmp(&extract(&a.message))
        });

        DiagnosticsReport {
            issues,
            files_checked,
            sources_run: vec!["high-complexity".into()],
            tool_errors: vec![],
            daemon_cached: false,
        }
    }
}

/// Count complexity using a tree-sitter query with `@complexity` captures.
fn count_complexity_with_query(
    node: &tree_sitter::Node,
    query: &tree_sitter::Query,
    content: &str,
) -> usize {
    let complexity_idx = query
        .capture_names()
        .iter()
        .position(|n| *n == "complexity");

    let Some(complexity_idx) = complexity_idx else {
        return 1;
    };

    let mut qcursor = tree_sitter::QueryCursor::new();
    qcursor.set_byte_range(node.byte_range());

    let mut complexity = 1usize;
    let mut matches = qcursor.matches(query, *node, content.as_bytes());
    while let Some(m) = matches.next() {
        for capture in m.captures {
            if capture.index as usize == complexity_idx {
                complexity += 1;
            }
        }
    }
    complexity
}

/// Build a `DiagnosticsReport` for the `high-complexity` rule.
///
/// Walks all source files under `root`, parses each with tree-sitter, and emits
/// an issue for every function whose cyclomatic complexity meets or exceeds the
/// threshold.
pub fn build_high_complexity_report(
    root: &Path,
    threshold: usize,
    explicit_files: Option<&[std::path::PathBuf]>,
    walk_config: &WalkConfig,
) -> DiagnosticsReport {
    let rule = HighComplexityRule { threshold };
    run_file_rule(&rule, root, explicit_files, walk_config)
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::io::Write as _;

    /// Write a Python file with a function containing `branch_count` if-branches,
    /// giving it cyclomatic complexity of `branch_count + 1`.
    fn make_python_function_with_branches(
        dir: &std::path::Path,
        name: &str,
        branch_count: usize,
    ) -> std::path::PathBuf {
        let path = dir.join(name);
        let mut f = std::fs::File::create(&path).unwrap();
        writeln!(f, "def complex_function(x):").unwrap();
        for i in 0..branch_count {
            writeln!(f, "    if x == {i}:").unwrap();
            writeln!(f, "        return {i}").unwrap();
        }
        writeln!(f, "    return -1").unwrap();
        path
    }

    #[test]
    fn test_default_threshold_not_triggered() {
        let dir = tempfile::tempdir().unwrap();
        // 19 branches → complexity 20; threshold is >= 20, so 19 branches (complexity 20) triggers.
        // Use 18 branches (complexity 19) to stay below default threshold of 20.
        let path = make_python_function_with_branches(dir.path(), "low.py", 18);
        let rule = HighComplexityRule { threshold: 20 };
        let findings = rule.check_file(&path, dir.path());
        assert!(
            findings.is_empty(),
            "complexity 19 should not trigger default threshold of 20; got {} findings",
            findings.len()
        );
    }

    #[test]
    fn test_default_threshold_triggered() {
        let dir = tempfile::tempdir().unwrap();
        // 19 branches → complexity 20 (base 1 + 19 branches); should trigger threshold of 20
        let path = make_python_function_with_branches(dir.path(), "high.py", 19);
        let rule = HighComplexityRule { threshold: 20 };
        let findings = rule.check_file(&path, dir.path());
        assert!(
            !findings.is_empty(),
            "complexity 20 should trigger default threshold of 20"
        );
    }

    #[test]
    fn test_custom_threshold_lower() {
        let dir = tempfile::tempdir().unwrap();
        // 5 branches → complexity 6; below default (20) but above custom threshold of 5
        let path = make_python_function_with_branches(dir.path(), "medium.py", 5);
        let rule = HighComplexityRule { threshold: 5 };
        let findings = rule.check_file(&path, dir.path());
        assert!(
            !findings.is_empty(),
            "complexity 6 should trigger custom threshold of 5"
        );
    }

    #[test]
    fn test_custom_threshold_higher() {
        let dir = tempfile::tempdir().unwrap();
        // 19 branches → complexity 20; at default (20) but below custom threshold of 30
        let path = make_python_function_with_branches(dir.path(), "medium.py", 19);
        let rule = HighComplexityRule { threshold: 30 };
        let findings = rule.check_file(&path, dir.path());
        assert!(
            findings.is_empty(),
            "complexity 20 should not trigger custom threshold of 30"
        );
    }
}