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, ChurnWindowUnit, 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_YEARS: u64 = 1;
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 =
40        SinceDuration::relative(ROUTING_CHURN_WINDOW_YEARS, ChurnWindowUnit::Years, "1 year");
41    let Some(churn_result) = analyze_churn(root, &since) else {
42        return RoutingFacts::default();
43    };
44
45    let ownership_cfg = &config.health.ownership;
46    let Ok(bot_globs) = compile_bot_globs(&ownership_cfg.bot_patterns) else {
47        return RoutingFacts::default();
48    };
49    let codeowners = CodeOwners::load(root, None).ok();
50    // Reuse the churn run's clock so routing and the health ownership block
51    // agree on "now" and neither flips a staleness threshold between runs.
52    let now_secs = churn_result.clock.epoch_secs();
53    let ctx = OwnershipContext {
54        author_pool: &churn_result.author_pool,
55        bot_globs: &bot_globs,
56        codeowners: codeowners.as_ref(),
57        email_mode: ownership_cfg.email_mode,
58        now_secs,
59    };
60
61    // The current reviewer (git user) is excluded from routing: you do not "ask
62    // yourself". On a solo repo every file routes to the author, so this is what
63    // turns "ask: bart (bus-factor 1)" on every decision into silence.
64    let self_ids = fallow_engine::repo_refs::current_user_identities(root);
65
66    let mut units: Vec<RoutingUnit> = changed_files
67        .iter()
68        .filter_map(|abs| route_one(abs, root, &churn_result, &ctx, &self_ids))
69        .collect();
70    units.sort_by(|a, b| a.file.cmp(&b.file));
71    RoutingFacts { units }
72}
73
74/// True when `expert` names the current reviewer (case-insensitive, `@`-tolerant
75/// so a CODEOWNERS `@handle` matches the bare git handle).
76fn expert_is_self(expert: &str, self_ids: &[String]) -> bool {
77    let normalized = expert.trim_start_matches('@').to_ascii_lowercase();
78    self_ids
79        .iter()
80        .any(|id| id.trim_start_matches('@').to_ascii_lowercase() == normalized)
81}
82
83/// Route a single changed file: resolve its experts and bus-factor flag from the
84/// ownership machinery. Returns `None` when the file has no churn record (no
85/// signal to route on).
86fn route_one(
87    abs: &Path,
88    root: &Path,
89    churn_result: &ChurnResult,
90    ctx: &OwnershipContext<'_>,
91    self_ids: &[String],
92) -> Option<RoutingUnit> {
93    let file_churn = churn_result.files.get(abs)?;
94    let relative = abs.strip_prefix(root).unwrap_or(abs);
95    let metrics = compute_ownership(file_churn, relative, ctx)?;
96
97    // Prefer the declared CODEOWNERS owner; otherwise the top contributor, then
98    // the suggested reviewers. Deduped, capped to keep the routing line tight.
99    let mut expert: Vec<String> = Vec::new();
100    if let Some(owner) = &metrics.declared_owner {
101        expert.push(owner.clone());
102    }
103    if expert.is_empty() {
104        expert.push(metrics.top_contributor.identifier.clone());
105        for reviewer in metrics.suggested_reviewers.iter().take(2) {
106            if !expert.contains(&reviewer.identifier) {
107                expert.push(reviewer.identifier.clone());
108            }
109        }
110    }
111
112    // Drop the current reviewer: there is no one to "ask" if you own it. A unit
113    // whose every expert is the reviewer carries no routing signal and is omitted
114    // (same doctrine as a file with no ownership signal), so a solo repo emits no
115    // routing noise.
116    expert.retain(|e| !expert_is_self(e, self_ids));
117    if expert.is_empty() {
118        return None;
119    }
120
121    Some(RoutingUnit {
122        file: relative.to_string_lossy().replace('\\', "/"),
123        expert,
124        bus_factor_one: metrics.bus_factor == 1,
125    })
126}
127
128#[cfg(test)]
129mod tests {
130    use fallow_output::{
131        ContributorEntry, ContributorIdentifierFormat, OwnershipMetrics, OwnershipState,
132    };
133
134    fn contributor(id: &str) -> ContributorEntry {
135        ContributorEntry {
136            identifier: id.to_string(),
137            format: ContributorIdentifierFormat::Handle,
138            share: 1.0,
139            stale_days: 1,
140            commits: 5,
141        }
142    }
143
144    fn metrics(declared: Option<&str>, bus_factor: u32) -> OwnershipMetrics {
145        OwnershipMetrics {
146            bus_factor,
147            contributor_count: 1,
148            top_contributor: contributor("alice"),
149            recent_contributors: vec![],
150            suggested_reviewers: vec![contributor("bob")],
151            declared_owner: declared.map(str::to_string),
152            unowned: None,
153            ownership_state: OwnershipState::Active,
154            drift: false,
155            drift_reason: None,
156        }
157    }
158
159    #[test]
160    fn current_reviewer_is_excluded_from_routing() {
161        let self_ids = vec![
162            "bart".to_string(),
163            "bart@waardenburg.dev".to_string(),
164            "Bart Waardenburg".to_string(),
165        ];
166        // The reviewer matches by handle, raw email, name, and CODEOWNERS @form,
167        // case-insensitively.
168        assert!(super::expert_is_self("bart", &self_ids));
169        assert!(super::expert_is_self("Bart", &self_ids));
170        assert!(super::expert_is_self("@bart", &self_ids));
171        assert!(super::expert_is_self("bart@waardenburg.dev", &self_ids));
172        // A different contributor is never self.
173        assert!(!super::expert_is_self("alice", &self_ids));
174        assert!(!super::expert_is_self("@team/ui", &self_ids));
175        // No identities -> never self (best-effort: git config unreadable).
176        assert!(!super::expert_is_self("bart", &[]));
177    }
178
179    /// `route_one`'s expert-selection logic, exercised through a small shim that
180    /// mirrors its branching without needing a live git repo.
181    fn select_expert(metrics: &OwnershipMetrics) -> (Vec<String>, bool) {
182        let mut expert: Vec<String> = Vec::new();
183        if let Some(owner) = &metrics.declared_owner {
184            expert.push(owner.clone());
185        }
186        if expert.is_empty() {
187            expert.push(metrics.top_contributor.identifier.clone());
188            for reviewer in metrics.suggested_reviewers.iter().take(2) {
189                if !expert.contains(&reviewer.identifier) {
190                    expert.push(reviewer.identifier.clone());
191                }
192            }
193        }
194        (expert, metrics.bus_factor == 1)
195    }
196
197    #[test]
198    fn declared_owner_wins() {
199        let (expert, _) = select_expert(&metrics(Some("@team/web"), 3));
200        assert_eq!(expert, vec!["@team/web".to_string()]);
201    }
202
203    #[test]
204    fn falls_back_to_git_contributors() {
205        let (expert, _) = select_expert(&metrics(None, 2));
206        assert_eq!(expert, vec!["alice".to_string(), "bob".to_string()]);
207    }
208
209    #[test]
210    fn bus_factor_one_is_flagged() {
211        let (_, bus1) = select_expert(&metrics(None, 1));
212        assert!(bus1);
213        let (_, bus2) = select_expert(&metrics(None, 2));
214        assert!(!bus2);
215    }
216}
fallow_api/routing.rs

fallow_api/
routing.rs
