istanbul-lib-instrument

import { createInstrumenter } from 'istanbul-lib-instrument'; const codeToInstrument = ` function calculate(a, b) { if (a > 0) { return a + b; } else { return b; } } const result = calculate(10, 5); console.log(result); `; const filename = '/app/src/example.js'; // Crucial for unique coverage reporting try { const instrumenter = createInstrumenter({ coverageVariable: '__CUSTOM_COVERAGE_OBJ__', // Define a custom global variable preserveComments: true, compact: false, // Output human-readable instrumented code esModules: true, // Enable ES module syntax support produceSourceMap: true // Generate a source map for remapping coverage }); const instrumentedCode = instrumenter.instrumentSync(codeToInstrument, filename); const sourceMap = instrumenter.lastSourceMap(); console.log('--- Original Code ---'); console.log(codeToInstrument); console.log('\n--- Instrumented Code ---'); console.log(instrumentedCode); console.log('\n--- Generated Source Map (snippet) ---'); // Source map objects can be large, showing a snippet for brevity console.log(JSON.stringify(sourceMap?.toJSON() || {}, null, 2).substring(0, 500) + '...'); // To obtain coverage, execute the instrumented code in a global context // where the coverage variable is defined, then retrieve it. // Example (Node.js): // global.__CUSTOM_COVERAGE_OBJ__ = {}; // eval(instrumentedCode); // console.log('\n--- Coverage Object (after execution) ---'); // console.log(JSON.stringify(global.__CUSTOM_COVERAGE_OBJ__, null, 2)); } catch (error) { console.error('Instrumentation failed:', error); }