fallow_api/
routing.rs

1//! Ownership-aware reviewer routing (6.D).
2//!
3//! Per changed file, name the expert(s) to route the review to: CODEOWNERS
4//! declared owner plus git-blame / recency contributors, and flag a bus-factor-1
5//! risk (the only qualified owner is one person). Reuses the health ownership /
6//! bus-factor machinery (`compute_ownership`, `CodeOwners`, churn) rather than a
7//! parallel implementation.
8//!
9//! This is the people-layer of the review direction: it answers "who do I ask?".
10//! Advisory brief data; never gates.
11
12use std::path::{Path, PathBuf};
13
14pub use fallow_output::{RoutingFacts, RoutingUnit};
15use rustc_hash::FxHashSet;
16
17use fallow_config::ResolvedConfig;
18use fallow_engine::churn::{ChurnResult, SinceDuration, analyze_churn};
19use fallow_engine::codeowners::CodeOwners;
20use fallow_engine::health::ownership::{OwnershipContext, compile_bot_globs, compute_ownership};
21
22/// Default churn window for routing: one year of history is enough to identify
23/// the per-file experts without an unbounded `git log`.
24const ROUTING_CHURN_WINDOW: &str = "1 year ago";
25
26/// Compute the routing section for the changed files. Best-effort: returns an
27/// empty `RoutingFacts` when churn is unavailable (non-git repo, shallow clone
28/// with no history). CODEOWNERS is consulted when present.
29#[must_use]
30#[allow(
31    clippy::implicit_hasher,
32    reason = "callers always pass the audit changed-file FxHashSet; generalizing the hasher adds noise"
33)]
34pub fn compute_routing(
35    root: &Path,
36    config: &ResolvedConfig,
37    changed_files: &FxHashSet<PathBuf>,
38) -> RoutingFacts {
39    let since = SinceDuration {
40        git_after: ROUTING_CHURN_WINDOW.to_string(),
41        display: "1 year".to_string(),
42    };
43    let Some(churn_result) = analyze_churn(root, &since) else {
44        return RoutingFacts::default();
45    };
46
47    let ownership_cfg = &config.health.ownership;
48    let Ok(bot_globs) = compile_bot_globs(&ownership_cfg.bot_patterns) else {
49        return RoutingFacts::default();
50    };
51    let codeowners = CodeOwners::load(root, None).ok();
52    let now_secs = std::time::SystemTime::now()
53        .duration_since(std::time::UNIX_EPOCH)
54        .unwrap_or_default()
55        .as_secs();
56    let ctx = OwnershipContext {
57        author_pool: &churn_result.author_pool,
58        bot_globs: &bot_globs,
59        codeowners: codeowners.as_ref(),
60        email_mode: ownership_cfg.email_mode,
61        now_secs,
62    };
63
64    // The current reviewer (git user) is excluded from routing: you do not "ask
65    // yourself". On a solo repo every file routes to the author, so this is what
66    // turns "ask: bart (bus-factor 1)" on every decision into silence.
67    let self_ids = fallow_engine::repo_refs::current_user_identities(root);
68
69    let mut units: Vec<RoutingUnit> = changed_files
70        .iter()
71        .filter_map(|abs| route_one(abs, root, &churn_result, &ctx, &self_ids))
72        .collect();
73    units.sort_by(|a, b| a.file.cmp(&b.file));
74    RoutingFacts { units }
75}
76
77/// True when `expert` names the current reviewer (case-insensitive, `@`-tolerant
78/// so a CODEOWNERS `@handle` matches the bare git handle).
79fn expert_is_self(expert: &str, self_ids: &[String]) -> bool {
80    let normalized = expert.trim_start_matches('@').to_ascii_lowercase();
81    self_ids
82        .iter()
83        .any(|id| id.trim_start_matches('@').to_ascii_lowercase() == normalized)
84}
85
86/// Route a single changed file: resolve its experts and bus-factor flag from the
87/// ownership machinery. Returns `None` when the file has no churn record (no
88/// signal to route on).
89fn route_one(
90    abs: &Path,
91    root: &Path,
92    churn_result: &ChurnResult,
93    ctx: &OwnershipContext<'_>,
94    self_ids: &[String],
95) -> Option<RoutingUnit> {
96    let file_churn = churn_result.files.get(abs)?;
97    let relative = abs.strip_prefix(root).unwrap_or(abs);
98    let metrics = compute_ownership(file_churn, relative, ctx)?;
99
100    // Prefer the declared CODEOWNERS owner; otherwise the top contributor, then
101    // the suggested reviewers. Deduped, capped to keep the routing line tight.
102    let mut expert: Vec<String> = Vec::new();
103    if let Some(owner) = &metrics.declared_owner {
104        expert.push(owner.clone());
105    }
106    if expert.is_empty() {
107        expert.push(metrics.top_contributor.identifier.clone());
108        for reviewer in metrics.suggested_reviewers.iter().take(2) {
109            if !expert.contains(&reviewer.identifier) {
110                expert.push(reviewer.identifier.clone());
111            }
112        }
113    }
114
115    // Drop the current reviewer: there is no one to "ask" if you own it. A unit
116    // whose every expert is the reviewer carries no routing signal and is omitted
117    // (same doctrine as a file with no ownership signal), so a solo repo emits no
118    // routing noise.
119    expert.retain(|e| !expert_is_self(e, self_ids));
120    if expert.is_empty() {
121        return None;
122    }
123
124    Some(RoutingUnit {
125        file: relative.to_string_lossy().replace('\\', "/"),
126        expert,
127        bus_factor_one: metrics.bus_factor == 1,
128    })
129}
130
131#[cfg(test)]
132mod tests {
133    use fallow_output::{
134        ContributorEntry, ContributorIdentifierFormat, OwnershipMetrics, OwnershipState,
135    };
136
137    fn contributor(id: &str) -> ContributorEntry {
138        ContributorEntry {
139            identifier: id.to_string(),
140            format: ContributorIdentifierFormat::Handle,
141            share: 1.0,
142            stale_days: 1,
143            commits: 5,
144        }
145    }
146
147    fn metrics(declared: Option<&str>, bus_factor: u32) -> OwnershipMetrics {
148        OwnershipMetrics {
149            bus_factor,
150            contributor_count: 1,
151            top_contributor: contributor("alice"),
152            recent_contributors: vec![],
153            suggested_reviewers: vec![contributor("bob")],
154            declared_owner: declared.map(str::to_string),
155            unowned: None,
156            ownership_state: OwnershipState::Active,
157            drift: false,
158            drift_reason: None,
159        }
160    }
161
162    #[test]
163    fn current_reviewer_is_excluded_from_routing() {
164        let self_ids = vec![
165            "bart".to_string(),
166            "bart@waardenburg.dev".to_string(),
167            "Bart Waardenburg".to_string(),
168        ];
169        // The reviewer matches by handle, raw email, name, and CODEOWNERS @form,
170        // case-insensitively.
171        assert!(super::expert_is_self("bart", &self_ids));
172        assert!(super::expert_is_self("Bart", &self_ids));
173        assert!(super::expert_is_self("@bart", &self_ids));
174        assert!(super::expert_is_self("bart@waardenburg.dev", &self_ids));
175        // A different contributor is never self.
176        assert!(!super::expert_is_self("alice", &self_ids));
177        assert!(!super::expert_is_self("@team/ui", &self_ids));
178        // No identities -> never self (best-effort: git config unreadable).
179        assert!(!super::expert_is_self("bart", &[]));
180    }
181
182    /// `route_one`'s expert-selection logic, exercised through a small shim that
183    /// mirrors its branching without needing a live git repo.
184    fn select_expert(metrics: &OwnershipMetrics) -> (Vec<String>, bool) {
185        let mut expert: Vec<String> = Vec::new();
186        if let Some(owner) = &metrics.declared_owner {
187            expert.push(owner.clone());
188        }
189        if expert.is_empty() {
190            expert.push(metrics.top_contributor.identifier.clone());
191            for reviewer in metrics.suggested_reviewers.iter().take(2) {
192                if !expert.contains(&reviewer.identifier) {
193                    expert.push(reviewer.identifier.clone());
194                }
195            }
196        }
197        (expert, metrics.bus_factor == 1)
198    }
199
200    #[test]
201    fn declared_owner_wins() {
202        let (expert, _) = select_expert(&metrics(Some("@team/web"), 3));
203        assert_eq!(expert, vec!["@team/web".to_string()]);
204    }
205
206    #[test]
207    fn falls_back_to_git_contributors() {
208        let (expert, _) = select_expert(&metrics(None, 2));
209        assert_eq!(expert, vec!["alice".to_string(), "bob".to_string()]);
210    }
211
212    #[test]
213    fn bus_factor_one_is_flagged() {
214        let (_, bus1) = select_expert(&metrics(None, 1));
215        assert!(bus1);
216        let (_, bus2) = select_expert(&metrics(None, 2));
217        assert!(!bus2);
218    }
219}
fallow_api/routing.rs

fallow_api/
routing.rs
