Crate oxc_coverage_instrument 

Istanbul-compatible JavaScript/TypeScript coverage instrumentation using the Oxc AST.

This crate parses JS/TS source with oxc_parser, identifies statements, functions, and branches, injects coverage counter expressions, and emits instrumented code. The coverage map output is compatible with Istanbul’s coverage-final.json format (consumed by Jest, Vitest, c8, nyc, Codecov).

Example

use oxc_coverage_instrument::{instrument, InstrumentOptions};

let source = "function add(a, b) { return a + b; }";
let result = instrument(source, "add.js", &InstrumentOptions::default()).unwrap();

println!("Instrumented code:\n{}", result.code);
println!("Functions found: {}", result.coverage_map.fn_map.len());

Coverage model

The coverage map tracks three dimensions:

• Statements: every executable statement gets a counter
• Functions: every function declaration, expression, arrow, and method
• Branches: if/else, ternary, switch cases, logical &&/||

Function names are derived from the same Oxc parser used by other Oxc-based tools, so they match consistently across the ecosystem.

Structs

BranchEntry

Branch entry in the coverage map.

FileCoverage

Coverage data for a single file. Serializes to Istanbul’s coverage-final.json format.

FnEntry

Function entry in the coverage map.

InstrumentOptions

Options for the instrument function.

InstrumentResult

Result of instrumenting a source file.

Location

A source location span with start and end positions.

Position

A 1-based line, 0-based column position.

UnhandledPragma

A coverage pragma comment that was found but not handled.

Enums

InstrumentError

Error type for instrumentation failures.

Functions

instrument

Instrument a JavaScript/TypeScript source file for coverage collection.

parse_coverage_map

Parse a coverage-final.json string into a map of file paths to coverage data.