README.md

oxc_coverage_report

Coverage summarization and the tree-visitor base for the oxc-coverage suite, a Rust port of istanbul-lib-report.

Overview

This crate consumes Istanbul-compatible coverage data, a CoverageMap parsed by oxc_coverage_types, summarizes hit counts into per-metric totals, and organizes per-file coverage into a folder and file ReportNode tree that a reporter walks via the Visitor trait.

The reporters themselves (text, text-summary, json-summary, lcov, cobertura, and html behind a feature flag) live in the sibling oxc_coverage_reports crate. Custom reporters implement Visitor directly against this crate.

Key Features

• summarize builds the report tree from a coverage map, grouping files into folder nodes.
• walk drives a Visitor over that tree, calling on_summary for folders and on_detail for files.
• CoverageSummary and Metric carry the covered, total, skipped, and percentage values for statements, branches, functions, and lines.

use oxc_coverage_types::parse_coverage_map;
use oxc_coverage_report::{summarize, walk, Visitor, ReportNode};

struct Counter { files: usize, folders: usize }
impl Visitor for Counter {
    fn on_detail(&mut self, _node: &ReportNode) -> std::io::Result<()> {
        self.files += 1;
        Ok(())
    }
    fn on_summary(&mut self, _node: &ReportNode) -> std::io::Result<()> {
        self.folders += 1;
        Ok(())
    }
}

let map = parse_coverage_map(json).unwrap();
let root = summarize(&map);
let mut visitor = Counter { files: 0, folders: 0 };
walk(&root, &mut visitor).unwrap();

Architecture

Summarization is a two-stage pass. The summarizer folds each FileCoverage into a CoverageSummary, then the tree builder groups files by common path prefix into ReportNodes of kind folder or file, rolling child summaries up into their parent. walk is a depth-first traversal over the finished tree, so a reporter never touches raw coverage entries and never has to reimplement percentage arithmetic.

Depend on this crate directly when writing a reporter that the suite does not already ship.