patchcov 0.4.0

//! The per-line coverage model that every parser produces.
//!
//! A [`CoverageReport`] is a map of repo-relative file paths to their
//! [`FileCoverage`], where each file records the hit count of every
//! *executable* line. Non-executable lines (blank, comment, declaration-only)
//! are simply absent — [`CoverageReport::hits`] returns `None` for them, which
//! callers use to exclude them from coverage denominators.

use std::collections::BTreeMap;
use std::path::Path;

/// Per-line hit counts for a single source file.
///
/// Only executable lines are present in `lines`; a line absent from the map is
/// not instrumented (blank, comment, etc.) and must not be counted towards
/// coverage totals.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct FileCoverage {
    /// Repo-relative path of the source file.
    pub path: String,
    /// Map of 1-based line number to hit count.
    pub lines: BTreeMap<u32, u64>,
    /// Opt-in lcov branch outcomes, keyed by line, block and branch identity.
    pub branches: BTreeMap<(u32, String, String), bool>,
    /// Opt-in Cobertura missed counts; aggregate counts cannot identify branches.
    pub missed_branches: BTreeMap<u32, u64>,
}

impl FileCoverage {
    /// Creates an empty file coverage for `path`.
    pub fn new(path: impl Into<String>) -> Self {
        Self {
            path: path.into(),
            lines: BTreeMap::new(),
            branches: BTreeMap::new(),
            missed_branches: BTreeMap::new(),
        }
    }

    /// Records `hits` for `line`. Repeated records for the same line take the
    /// maximum, so a line covered by any region counts as covered.
    pub fn record(&mut self, line: u32, hits: u64) {
        self.lines
            .entry(line)
            .and_modify(|h| *h = (*h).max(hits))
            .or_insert(hits);
    }

    /// Merges line hits and branch evidence without scoring until all shards arrive.
    fn merge(&mut self, other: Self) {
        for (line, hits) in other.lines {
            self.record(line, hits);
        }
        for (key, covered) in other.branches {
            self.branches
                .entry(key)
                .and_modify(|v| *v |= covered)
                .or_insert(covered);
        }
        for (line, missed) in other.missed_branches {
            self.missed_branches
                .entry(line)
                .and_modify(|v| *v = (*v).max(missed))
                .or_insert(missed);
        }
    }

    /// Number of executable lines.
    pub fn total_lines(&self) -> u64 {
        self.lines.len() as u64
    }

    /// Number of executable lines hit at least once.
    pub fn covered_lines(&self) -> u64 {
        self.lines.values().filter(|&&h| h > 0).count() as u64
    }

    /// Line coverage percentage, or `None` when the file has no executable lines.
    pub fn percent(&self) -> Option<f64> {
        let total = self.total_lines();
        if total == 0 {
            None
        } else {
            Some(self.covered_lines() as f64 / total as f64 * 100.0)
        }
    }
}

/// A whole coverage report: repo-relative file path → [`FileCoverage`].
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct CoverageReport {
    /// Per-file coverage, keyed by repo-relative path.
    pub files: BTreeMap<String, FileCoverage>,
}

impl CoverageReport {
    /// Creates an empty report.
    pub fn new() -> Self {
        Self::default()
    }

    /// Inserts or merges a file's coverage into the report.
    ///
    /// If the path already exists, line hit counts are merged (taking the max
    /// per line), which keeps the model robust against reports that split one
    /// file across multiple records.
    pub fn insert(&mut self, file: FileCoverage) {
        match self.files.get_mut(&file.path) {
            Some(existing) => {
                existing.merge(file);
            }
            None => {
                self.files.insert(file.path.clone(), file);
            }
        }
    }

    /// Merges `other` into this report: the files are unioned and a line present
    /// in both takes the larger hit count.
    ///
    /// This is the rule for combining the reports of a sharded coverage run. It
    /// is a union, so a line only one report instrumented keeps that report's
    /// count rather than being scored against the other. Hit counts are maxed,
    /// not summed: coverage is a covered-or-not question and nothing in the
    /// line-coverage output reads the count itself.
    pub fn merge(&mut self, other: Self) {
        for file in other.files.into_values() {
            self.insert(file);
        }
    }

    /// Hit count for `path`:`line`, or `None` when the line is not instrumented
    /// (or the file is absent from the report).
    pub fn hits(&self, path: &str, line: u32) -> Option<u64> {
        self.files
            .get(path)
            .and_then(|f| f.lines.get(&line).copied())
    }

    /// Scores any executable line with missed branches as uncovered.
    /// Call only after merging shards; applying this before merging loses outcomes.
    pub fn apply_branch_coverage(&mut self) {
        for file in self.files.values_mut() {
            for (&(line, _, _), &covered) in &file.branches {
                if !covered {
                    if let Some(hits) = file.lines.get_mut(&line) {
                        *hits = 0;
                    }
                }
            }
            for (&line, &missed) in &file.missed_branches {
                if missed > 0 {
                    if let Some(hits) = file.lines.get_mut(&line) {
                        *hits = 0;
                    }
                }
            }
        }
    }

    /// Total executable lines across all files.
    pub fn total_lines(&self) -> u64 {
        self.files.values().map(FileCoverage::total_lines).sum()
    }

    /// Total covered lines across all files.
    pub fn covered_lines(&self) -> u64 {
        self.files.values().map(FileCoverage::covered_lines).sum()
    }

    /// Project-wide line coverage percentage, or `None` when there are no
    /// executable lines.
    pub fn percent(&self) -> Option<f64> {
        let total = self.total_lines();
        if total == 0 {
            None
        } else {
            Some(self.covered_lines() as f64 / total as f64 * 100.0)
        }
    }

    /// Normalises every file path to be repo-relative.
    ///
    /// Coverage tools usually emit absolute paths (lcov `SF:`, llvm-cov
    /// `filename`). Stripping `prefix` mirrors the CI `jq ltrimstr($ws)` step so
    /// the paths line up with the repo-relative paths git diffs report. Paths
    /// that do not start with `prefix` are left unchanged (already relative, or
    /// outside the tree). Leading `./` and `/` are also trimmed.
    pub fn strip_prefix(&mut self, prefix: &Path) {
        let prefix_str = prefix.to_string_lossy();
        let prefix_slash = format!("{}/", prefix_str.trim_end_matches('/'));
        let mut remapped: BTreeMap<String, FileCoverage> = BTreeMap::new();
        for (_, mut file) in std::mem::take(&mut self.files) {
            let normalized = normalize_path(&file.path, &prefix_slash);
            file.path.clone_from(&normalized);
            // Merge in case two source paths normalise to the same repo path.
            match remapped.get_mut(&normalized) {
                Some(existing) => {
                    existing.merge(file);
                }
                None => {
                    remapped.insert(normalized, file);
                }
            }
        }
        self.files = remapped;
    }

    /// Drops every file whose path does not satisfy `keep`.
    ///
    /// Used to apply `--ignore-filename-regex`: because it is called *after*
    /// [`strip_prefix`](Self::strip_prefix), the predicate sees repo-relative
    /// paths — the same space git diffs report in — so head and baseline
    /// reports are filtered identically before any delta is computed.
    ///
    /// Returns the files that were dropped, so the caller can report what the
    /// filter removed rather than leave a reader to infer it from a smaller total.
    pub fn retain_paths<F>(&mut self, keep: F) -> Vec<FileCoverage>
    where
        F: Fn(&str) -> bool,
    {
        let (kept, dropped): (BTreeMap<_, _>, BTreeMap<_, _>) = std::mem::take(&mut self.files)
            .into_iter()
            .partition(|(path, _)| keep(path));
        self.files = kept;
        dropped.into_values().collect()
    }

    /// Drops every line for which `keep` returns `false`, then drops any file
    /// left with no executable lines.
    ///
    /// The line-level twin of [`retain_paths`](Self::retain_paths), used to
    /// apply `ignore` source markers. Like the path filter it runs *after*
    /// [`strip_prefix`](Self::strip_prefix), so the predicate sees repo-relative
    /// paths, and it is applied to head and baseline independently — each from
    /// its own revision's source, since a region moves between revisions.
    ///
    /// Emptied files are removed rather than kept at zero lines: a
    /// [`FileCoverage`] with no lines has `percent() == None`, which
    /// `FileDelta::delta` reads as a fall to zero — so a fully-ignored file
    /// would render as a *total loss of coverage*, the exact opposite of what
    /// ignoring it means.
    pub fn retain_lines<F>(&mut self, keep: F)
    where
        F: Fn(&str, u32) -> bool,
    {
        for (path, file) in &mut self.files {
            file.lines.retain(|&line, _| keep(path, line));
            file.branches
                .retain(|(line, _, _), _| file.lines.contains_key(line));
            file.missed_branches
                .retain(|line, _| file.lines.contains_key(line));
        }
        self.files.retain(|_, file| file.total_lines() > 0);
    }
}

/// Strips `prefix_slash` (a trailing-slash directory prefix) from `path`, then
/// trims any leading `./` or `/`.
fn normalize_path(path: &str, prefix_slash: &str) -> String {
    let stripped = path.strip_prefix(prefix_slash).unwrap_or(path);
    stripped
        .trim_start_matches("./")
        .trim_start_matches('/')
        .to_string()
}

#[cfg(test)]
#[allow(clippy::unwrap_used, clippy::expect_used)]
mod tests {
    use super::*;

    #[test]
    fn record_takes_max_hits() {
        let mut f = FileCoverage::new("src/a.rs");
        f.record(1, 0);
        f.record(1, 3);
        f.record(1, 1);
        assert_eq!(f.lines.get(&1), Some(&3));
    }

    #[test]
    fn percent_counts_only_executable_lines() {
        let mut f = FileCoverage::new("src/a.rs");
        f.record(1, 1);
        f.record(2, 0);
        f.record(3, 5);
        // 2 of 3 executable lines covered.
        assert_eq!(f.total_lines(), 3);
        assert_eq!(f.covered_lines(), 2);
        assert!((f.percent().unwrap() - 66.666_666).abs() < 1e-3);
    }

    #[test]
    fn empty_file_has_no_percent() {
        let f = FileCoverage::new("src/empty.rs");
        assert_eq!(f.percent(), None);
    }

    #[test]
    fn hits_distinguishes_uncovered_from_non_executable() {
        let mut report = CoverageReport::new();
        let mut f = FileCoverage::new("src/a.rs");
        f.record(10, 0); // executable but uncovered
        report.insert(f);
        assert_eq!(report.hits("src/a.rs", 10), Some(0)); // uncovered
        assert_eq!(report.hits("src/a.rs", 11), None); // not instrumented
        assert_eq!(report.hits("src/missing.rs", 1), None);
    }

    #[test]
    fn insert_merges_duplicate_paths() {
        let mut report = CoverageReport::new();
        let mut a = FileCoverage::new("src/a.rs");
        a.record(1, 0);
        let mut b = FileCoverage::new("src/a.rs");
        b.record(1, 2);
        b.record(2, 1);
        report.insert(a);
        report.insert(b);
        assert_eq!(report.files.len(), 1);
        assert_eq!(report.hits("src/a.rs", 1), Some(2));
        assert_eq!(report.hits("src/a.rs", 2), Some(1));
    }

    #[test]
    fn merge_unions_files_and_takes_the_max_per_line() {
        let mut shard_a = CoverageReport::new();
        let mut a = FileCoverage::new("src/shared.rs");
        a.record(1, 3);
        a.record(2, 0);
        shard_a.insert(a);
        let mut only_a = FileCoverage::new("src/only_a.rs");
        only_a.record(1, 1);
        shard_a.insert(only_a);

        let mut shard_b = CoverageReport::new();
        let mut b = FileCoverage::new("src/shared.rs");
        b.record(1, 0);
        b.record(2, 7);
        b.record(3, 0);
        shard_b.insert(b);
        let mut only_b = FileCoverage::new("src/only_b.rs");
        only_b.record(1, 0);
        shard_b.insert(only_b);

        shard_a.merge(shard_b);

        assert_eq!(shard_a.files.len(), 3);
        // Line 1 was hit only in shard A, line 2 only in shard B: both count as covered.
        assert_eq!(shard_a.hits("src/shared.rs", 1), Some(3));
        assert_eq!(shard_a.hits("src/shared.rs", 2), Some(7));
        // A line only one shard instrumented keeps that shard's count.
        assert_eq!(shard_a.hits("src/shared.rs", 3), Some(0));
        assert_eq!(shard_a.hits("src/only_a.rs", 1), Some(1));
        assert_eq!(shard_a.hits("src/only_b.rs", 1), Some(0));
    }

    #[test]
    fn merge_is_order_independent() {
        let report = |lines: &[(u32, u64)]| {
            let mut r = CoverageReport::new();
            let mut f = FileCoverage::new("src/a.rs");
            for &(line, hits) in lines {
                f.record(line, hits);
            }
            r.insert(f);
            r
        };
        let mut ab = report(&[(1, 1), (2, 0)]);
        ab.merge(report(&[(1, 0), (2, 4)]));
        let mut ba = report(&[(1, 0), (2, 4)]);
        ba.merge(report(&[(1, 1), (2, 0)]));
        assert_eq!(ab, ba);
    }

    #[test]
    fn project_percent_aggregates_files() {
        let mut report = CoverageReport::new();
        let mut a = FileCoverage::new("src/a.rs");
        a.record(1, 1);
        a.record(2, 1);
        let mut b = FileCoverage::new("src/b.rs");
        b.record(1, 0);
        b.record(2, 0);
        report.insert(a);
        report.insert(b);
        assert_eq!(report.total_lines(), 4);
        assert_eq!(report.covered_lines(), 2);
        assert_eq!(report.percent(), Some(50.0));
    }

    #[test]
    fn strip_prefix_makes_paths_repo_relative() {
        let mut report = CoverageReport::new();
        let mut f = FileCoverage::new("/home/runner/work/patchcov/patchcov/src/a.rs");
        f.record(1, 1);
        report.insert(f);
        report.strip_prefix(Path::new("/home/runner/work/patchcov/patchcov"));
        assert!(report.files.contains_key("src/a.rs"));
    }

    #[test]
    fn strip_prefix_merges_colliding_paths() {
        // Two distinct source paths that normalise to the same repo path.
        let mut report = CoverageReport::new();
        let mut a = FileCoverage::new("/root/src/a.rs");
        a.record(1, 0);
        let mut b = FileCoverage::new("/root/./src/a.rs");
        b.record(2, 1);
        report.insert(a);
        report.insert(b);
        assert_eq!(report.files.len(), 2);
        report.strip_prefix(Path::new("/root"));
        assert_eq!(report.files.len(), 1);
        assert_eq!(report.hits("src/a.rs", 1), Some(0));
        assert_eq!(report.hits("src/a.rs", 2), Some(1));
    }

    #[test]
    fn strip_prefix_leaves_relative_paths() {
        let mut report = CoverageReport::new();
        let mut f = FileCoverage::new("./src/a.rs");
        f.record(1, 1);
        report.insert(f);
        report.strip_prefix(Path::new("/some/other/root"));
        assert!(report.files.contains_key("src/a.rs"));
    }

    #[test]
    fn retain_lines_drops_only_the_named_lines() {
        let mut report = CoverageReport::new();
        let mut f = FileCoverage::new("src/a.rs");
        f.record(1, 1);
        f.record(2, 0);
        f.record(3, 5);
        report.insert(f);
        report.retain_lines(|path, line| !(path == "src/a.rs" && line == 2));
        assert_eq!(report.hits("src/a.rs", 1), Some(1));
        assert_eq!(report.hits("src/a.rs", 2), None);
        assert_eq!(report.hits("src/a.rs", 3), Some(5));
        assert_eq!(report.total_lines(), 2);
    }

    /// A file whose every line is ignored must leave the report entirely. Kept
    /// at zero lines its `percent()` is `None`, which `FileDelta::delta` reads
    /// as a fall to zero — an ignored file would render as a total loss of
    /// coverage.
    #[test]
    fn retain_lines_removes_files_left_empty() {
        let mut report = CoverageReport::new();
        for path in ["src/a.rs", "src/gated.rs"] {
            let mut f = FileCoverage::new(path);
            f.record(1, 1);
            report.insert(f);
        }
        report.retain_lines(|path, _| path != "src/gated.rs");
        assert!(report.files.contains_key("src/a.rs"));
        assert!(
            !report.files.contains_key("src/gated.rs"),
            "a file with no lines left must be dropped, not kept at 0%"
        );
    }

    #[test]
    fn retain_paths_drops_non_matching_files() {
        let mut report = CoverageReport::new();
        for path in ["src/a.rs", "src/gpu/mlx.rs", "src/b.rs"] {
            let mut f = FileCoverage::new(path);
            f.record(1, 1);
            report.insert(f);
        }
        let dropped = report.retain_paths(|path| !path.contains("gpu/"));
        assert!(report.files.contains_key("src/a.rs"));
        assert!(report.files.contains_key("src/b.rs"));
        assert!(!report.files.contains_key("src/gpu/mlx.rs"));
        assert_eq!(dropped.len(), 1);
        assert_eq!(dropped[0].path, "src/gpu/mlx.rs");
        assert_eq!(
            dropped[0].lines.len(),
            1,
            "the dropped file keeps its lines"
        );
    }
    #[test]
    fn branch_evidence_survives_aliases_merges_and_line_filters() {
        let mut a = crate::lcov::parse_with_branches("SF:/root/a.rs\nDA:1,1\nDA:2,1\nBRDA:1,0,0,1\nBRDA:1,0,1,0\nBRDA:2,0,0,0\nend_of_record").unwrap();
        let b = crate::lcov::parse_with_branches(
            "SF:/root/./a.rs\nDA:1,2\nBRDA:1,0,0,0\nBRDA:1,0,1,1\nend_of_record",
        )
        .unwrap();
        a.merge(b);
        a.strip_prefix(Path::new("/root"));
        a.retain_lines(|_, line| line != 2);
        assert_eq!(a.files["a.rs"].branches.len(), 2);
        a.apply_branch_coverage();
        assert_eq!(a.hits("a.rs", 1), Some(2));
        assert_eq!(a.hits("a.rs", 2), None);
    }

    #[test]
    fn mapped_aliases_keep_partial_branch_evidence() {
        let mut report = crate::lcov::parse_with_branches(
            "SF:pkg/a.rs\nDA:1,1\nBRDA:1,0,0,0\nend_of_record\nSF:a.rs\nDA:1,2\nend_of_record",
        )
        .unwrap();
        report
            .map_paths(&[crate::paths::PathMapping {
                from: "pkg".into(),
                to: String::new(),
            }])
            .unwrap();
        report.apply_branch_coverage();
        assert_eq!(report.hits("a.rs", 1), Some(0));
    }
}