remap-istanbul/lib/getMapping.js

A tool for remapping Istanbul coverage via Source Maps

const { SourceMapConsumer } = require('source-map');

/**
 * A function that determines the original position for a given location
 * @param  {SourceMapConsumer} sourceMap        The source map
 * @param  {Object}            location         The original location Object
 * @return {Object}                             The remapped location Object
 */
module.exports = function getMapping(sourceMap, location) {
	/* istanbul ignore if: edge case too hard to test for with babel malformation */
	if (location.start.line < 1 || location.start.column < 0) {
		return null;
	}
	/* istanbul ignore if: edge case too hard to test for with babel malformation */
	if (location.end.line < 1 || location.end.column < 0) {
		return null;
	}

	const start = sourceMap.originalPositionFor(location.start);
	let end = sourceMap.originalPositionFor(location.end);

	/* istanbul ignore if: edge case too hard to test for */
	if (!start || !end) {
		return null;
	}
	if (!start.source || !end.source || start.source !== end.source) {
		return null;
	}
	/* istanbul ignore if: edge case too hard to test for */
	if (start.line === null || start.column === null) {
		return null;
	}
	/* istanbul ignore if: edge case too hard to test for */
	if (end.line === null || end.column === null) {
		return null;
	}

	if (start.line === end.line && start.column === end.column) {
		end = sourceMap.originalPositionFor({
			line: location.end.line,
			column: location.end.column,
			bias: SourceMapConsumer.LEAST_UPPER_BOUND,
		});
		end.column -= 1;
	}

	return {
		source: start.source,
		loc: {
			start: {
				line: start.line,
				column: start.column,
			},
			end: {
				line: end.line,
				column: end.column,
			},
			skip: location.skip,
		},
	};
};