codelens_engine/
redundant_definitions.rs

1//! Detects "thin wrapper" definitions — functions whose entire body is a
2//! single call to another function with one literal default argument
3//! (e.g. `pub fn record_X(&self) { self.record_X_for_session(None) }`).
4//!
5//! This is a syntactic-only detector that catches the exact pattern flagged
6//! by self-dogfooding in v1.13.0 Phase 1-A: 16 `record_*` wrappers all
7//! forwarding to their `_for_session(None)` substrate. The substrate could
8//! be flagged by `find_dead_code_v2` only AFTER the wrappers were removed,
9//! so this complement helps surface the cluster pre-deletion.
10
11use crate::project::{collect_files, ProjectRoot};
12use anyhow::Result;
13use regex::Regex;
14use serde::Serialize;
15use std::path::Path;
16use std::sync::LazyLock;
17
18/// Matches a Rust one-line wrapper:
19///   `pub fn NAME(args) [-> RetType] { self.OTHER(args, LITERAL) [;] }`
20///   `fn NAME(args) [-> RetType] { OTHER(args, LITERAL) [;] }`
21/// where LITERAL is one of: `None`, `Default::default()`, `false`, `true`,
22/// a bare integer literal, or a quoted string literal.
23static RUST_ONE_LINE_WRAPPER_RE: LazyLock<Regex> = LazyLock::new(|| {
24    // (?m): multiline (^/$ are line anchors)
25    Regex::new(
26        r#"(?m)^\s*(?:pub(?:\([^)]*\))?\s+)?fn\s+(?P<wrapper>[A-Za-z_][A-Za-z0-9_]*)\s*\([^)]*\)\s*(?:->\s*[^{]+?)?\s*\{\s*(?:self\.|Self::)?(?P<target>[A-Za-z_][A-Za-z0-9_]*)\s*\([^)]*?(?P<default>None|Default::default\(\)|true|false|-?\d+|"[^"]*")?\s*\)\s*;?\s*\}\s*$"#
27    ).unwrap()
28});
29
30#[derive(Debug, Clone, Serialize, PartialEq, Eq)]
31pub struct RedundantDefinitionEntry {
32    pub file: String,
33    pub wrapper: String,
34    pub target: String,
35    pub line: usize,
36    pub default_arg: Option<String>,
37    pub kind: &'static str,
38}
39
40/// Finds Rust one-line wrappers in the project.
41///
42/// Returns a list of (wrapper, target) pairs. Callers can group by `target`
43/// to find substrates with multiple wrappers — the highest-leverage cleanup
44/// opportunity per Phase 1-A's findings.
45pub fn find_redundant_definitions(
46    project: &ProjectRoot,
47    max_results: usize,
48) -> Result<Vec<RedundantDefinitionEntry>> {
49    let mut results: Vec<RedundantDefinitionEntry> = Vec::new();
50    let candidates = collect_files(project.as_path(), is_rust_file)?;
51
52    for path in &candidates {
53        let source = match std::fs::read_to_string(path) {
54            Ok(s) => s,
55            Err(_) => continue,
56        };
57        let relative = project.to_relative(path);
58        if is_test_file(&relative) {
59            continue;
60        }
61        let production_source = strip_cfg_test_modules(&source);
62        scan_rust_source(&production_source, &relative, &mut results);
63        if max_results > 0 && results.len() >= max_results {
64            break;
65        }
66    }
67
68    results.sort_by(|a, b| {
69        a.target
70            .cmp(&b.target)
71            .then(a.file.cmp(&b.file))
72            .then(a.line.cmp(&b.line))
73    });
74    if max_results > 0 && results.len() > max_results {
75        results.truncate(max_results);
76    }
77    Ok(results)
78}
79
80fn scan_rust_source(source: &str, file: &str, out: &mut Vec<RedundantDefinitionEntry>) {
81    for m in RUST_ONE_LINE_WRAPPER_RE.captures_iter(source) {
82        let wrapper = m
83            .name("wrapper")
84            .map(|m| m.as_str().to_owned())
85            .unwrap_or_default();
86        let target = m
87            .name("target")
88            .map(|m| m.as_str().to_owned())
89            .unwrap_or_default();
90        if wrapper.is_empty() || target.is_empty() || wrapper == target {
91            continue;
92        }
93        let default_arg = m.name("default").map(|m| m.as_str().to_owned());
94        let line = byte_offset_to_line(source, m.get(0).map(|m| m.start()).unwrap_or(0));
95        out.push(RedundantDefinitionEntry {
96            file: file.to_owned(),
97            wrapper,
98            target,
99            line,
100            default_arg,
101            kind: "rust_one_line_wrapper",
102        });
103    }
104}
105
106fn byte_offset_to_line(source: &str, offset: usize) -> usize {
107    source[..offset.min(source.len())].matches('\n').count() + 1
108}
109
110fn is_rust_file(path: &Path) -> bool {
111    path.extension().and_then(|s| s.to_str()) == Some("rs")
112}
113
114/// Skip canonical test/example/bench harness files. Heuristic: any path
115/// segment named `tests`, `bench`, `benches`, `examples`, or any file
116/// ending in `_tests.rs`/`_test.rs`. Self-detector module is also
117/// skipped to avoid flagging its own fixture strings.
118fn is_test_file(relative: &str) -> bool {
119    if relative == "crates/codelens-engine/src/redundant_definitions.rs" {
120        return true;
121    }
122    let lower = relative.to_ascii_lowercase();
123    if lower.ends_with("_tests.rs") || lower.ends_with("_test.rs") {
124        return true;
125    }
126    lower.split('/').any(|seg| {
127        matches!(
128            seg,
129            "tests" | "test" | "bench" | "benches" | "examples" | "fixtures"
130        )
131    })
132}
133
134/// Removes `#[cfg(test)] mod ... { ... }` blocks (matched by regex with
135/// nested braces handled by depth counting). This filters out test-only
136/// helper functions that share the wrapper shape but are not production
137/// code paths.
138fn strip_cfg_test_modules(source: &str) -> String {
139    let mut out = String::with_capacity(source.len());
140    let mut chars = source.char_indices().peekable();
141    while let Some(&(idx, ch)) = chars.peek() {
142        if ch == '#' {
143            // try to match #[cfg(test)] mod NAME {
144            let rest = &source[idx..];
145            if let Some(open_brace_offset) = match_cfg_test_mod_header(rest) {
146                let body_start = idx + open_brace_offset;
147                let body_end = match find_matching_brace(source, body_start) {
148                    Some(e) => e,
149                    None => {
150                        out.push(ch);
151                        chars.next();
152                        continue;
153                    }
154                };
155                // skip over the entire `#[cfg(test)] mod NAME { ... }`
156                while let Some(&(j, _)) = chars.peek() {
157                    if j > body_end {
158                        break;
159                    }
160                    chars.next();
161                }
162                continue;
163            }
164        }
165        out.push(ch);
166        chars.next();
167    }
168    out
169}
170
171/// If `rest` starts with `#[cfg(test)] mod NAME {`, return the byte
172/// offset of the `{`. Otherwise None. Tolerant of attribute whitespace
173/// variants but not of comments inside the attribute.
174fn match_cfg_test_mod_header(rest: &str) -> Option<usize> {
175    static HEADER_RE: LazyLock<Regex> = LazyLock::new(|| {
176        Regex::new(r"^#\s*\[\s*cfg\s*\(\s*test\s*\)\s*\]\s*(?:pub(?:\([^)]*\))?\s+)?mod\s+[A-Za-z_][A-Za-z0-9_]*\s*\{")
177            .unwrap()
178    });
179    HEADER_RE.find(rest).map(|m| m.end() - 1)
180}
181
182/// Returns the byte index of the matching `}` for the `{` at `open_idx`.
183fn find_matching_brace(source: &str, open_idx: usize) -> Option<usize> {
184    let bytes = source.as_bytes();
185    if bytes.get(open_idx) != Some(&b'{') {
186        return None;
187    }
188    let mut depth = 1usize;
189    let mut i = open_idx + 1;
190    while i < bytes.len() {
191        match bytes[i] {
192            b'{' => depth += 1,
193            b'}' => {
194                depth -= 1;
195                if depth == 0 {
196                    return Some(i);
197                }
198            }
199            _ => {}
200        }
201        i += 1;
202    }
203    None
204}
205
206#[cfg(test)]
207mod tests {
208    use super::*;
209
210    #[test]
211    fn detects_self_dot_wrapper_with_none_default() {
212        let source = r#"
213impl Foo {
214    pub fn record_x(&self) { self.record_x_for_session(None) }
215    pub fn record_y(&self) { self.record_y_for_session(None); }
216}
217        "#;
218        let mut out = Vec::new();
219        scan_rust_source(source, "telemetry.rs", &mut out);
220        assert_eq!(out.len(), 2, "got: {:?}", out);
221        assert_eq!(out[0].wrapper, "record_x");
222        assert_eq!(out[0].target, "record_x_for_session");
223        assert_eq!(out[0].default_arg.as_deref(), Some("None"));
224        assert_eq!(out[1].wrapper, "record_y");
225    }
226
227    #[test]
228    fn detects_bare_function_wrapper() {
229        let source = r#"
230pub fn helper(x: u32) -> bool { inner(x, false) }
231        "#;
232        let mut out = Vec::new();
233        scan_rust_source(source, "lib.rs", &mut out);
234        assert_eq!(out.len(), 1);
235        assert_eq!(out[0].wrapper, "helper");
236        assert_eq!(out[0].target, "inner");
237        assert_eq!(out[0].default_arg.as_deref(), Some("false"));
238    }
239
240    #[test]
241    fn skips_self_recursive_call() {
242        let source = r#"
243pub fn loop_me(&self) { self.loop_me(0) }
244        "#;
245        let mut out = Vec::new();
246        scan_rust_source(source, "x.rs", &mut out);
247        // wrapper == target → not flagged (would be infinite recursion, not delegation)
248        assert!(out.is_empty(), "got: {:?}", out);
249    }
250
251    #[test]
252    fn strip_cfg_test_modules_removes_test_block() {
253        let source = r#"
254pub fn real_thing(&self) { self.real_thing_inner(None) }
255
256#[cfg(test)]
257mod tests {
258    fn helper() { foo(true) }
259}
260"#;
261        let stripped = super::strip_cfg_test_modules(source);
262        assert!(stripped.contains("real_thing"));
263        assert!(
264            !stripped.contains("foo(true)"),
265            "test mod should be gone: {}",
266            stripped
267        );
268    }
269
270    #[test]
271    fn is_test_file_recognizes_canonical_paths() {
272        assert!(super::is_test_file("crates/foo/tests/something.rs"));
273        assert!(super::is_test_file("crates/foo/src/internals_tests.rs"));
274        assert!(super::is_test_file("benchmarks/bench/runner.rs"));
275        assert!(!super::is_test_file("crates/foo/src/main.rs"));
276        assert!(super::is_test_file(
277            "crates/codelens-engine/src/redundant_definitions.rs"
278        ));
279    }
280
281    #[test]
282    #[ignore]
283    fn dogfood_self_repo() {
284        // Run with: cargo test -p codelens-engine dogfood_self_repo -- --ignored --nocapture
285        let repo = std::env::var("CODELENS_REPO_ROOT")
286            .unwrap_or_else(|_| "/Users/bagjaeseog/codelens-mcp-plugin".to_owned());
287        let project = crate::project::ProjectRoot::new(repo).expect("project root");
288        let results =
289            super::find_redundant_definitions(&project, 200).expect("find_redundant_definitions");
290        eprintln!(
291            "\n=== {} redundant definitions in self (post v2 filtering) ===\n",
292            results.len()
293        );
294        let mut groups: std::collections::BTreeMap<&str, Vec<&RedundantDefinitionEntry>> =
295            std::collections::BTreeMap::new();
296        for r in &results {
297            groups.entry(r.target.as_str()).or_default().push(r);
298        }
299        let mut multi: Vec<_> = groups.iter().filter(|(_, v)| v.len() >= 2).collect();
300        multi.sort_by(|a, b| b.1.len().cmp(&a.1.len()));
301        eprintln!("Multi-wrapper clusters: {}\n", multi.len());
302        for (target, members) in &multi {
303            eprintln!("  {} ← {}", target, members.len());
304            for m in members.iter().take(3) {
305                eprintln!("      {} at {}:{}", m.wrapper, m.file, m.line);
306            }
307            if members.len() > 3 {
308                eprintln!("      ... +{} more", members.len() - 3);
309            }
310        }
311        eprintln!("\nFirst 30 hits:\n");
312        for r in results.iter().take(30) {
313            eprintln!("  {} -> {}  ({}:{})", r.wrapper, r.target, r.file, r.line);
314        }
315    }
316
317    #[test]
318    fn skips_multi_statement_body() {
319        let source = r#"
320pub fn complex(&self) {
321    let x = 1;
322    self.do_thing(x, None);
323}
324        "#;
325        let mut out = Vec::new();
326        scan_rust_source(source, "x.rs", &mut out);
327        assert!(
328            out.is_empty(),
329            "multi-statement should not match: {:?}",
330            out
331        );
332    }
333}
codelens_engine/redundant_definitions.rs

codelens_engine/
redundant_definitions.rs
