generate-source-map.js

const path = require('path');
const sourceMap = require('source-map');

const splitRE = /\r?\n/g;

module.exports = function generateSourceMap(
    scriptResult,
    src,
    filename,
    renderFnStartLine,
    renderFnEndLine,
    templateLine,
) {
    const file = path.basename(filename);
    const map = new sourceMap.SourceMapGenerator();

    const scriptFromExternalSrc = scriptResult && scriptResult.externalSrc;

    // If script uses external file for content (using the src attribute) then
    // map result to this file, instead of original.
    const srcContent = scriptFromExternalSrc ? scriptResult.externalSrc : src;

    map.setSourceContent(file, srcContent);
    if (scriptResult) {
        const inputMapConsumer =
            scriptResult.map && new sourceMap.SourceMapConsumer(scriptResult.map);
        scriptResult.code.split(splitRE).forEach((line, index) => {
            const ln = index + 1;
            const originalLine = inputMapConsumer ?
                inputMapConsumer.originalPositionFor({ line: ln, column: 0 }).line :
                ln;
            if (originalLine) {
                map.addMapping({
                    source: file,
                    generated: {
                        line: ln,
                        column: 0,
                    },
                    original: {
                        line: originalLine,
                        column: 0,
                    },
                });
            }
        });
    }

    // If script is from external src then the source map will only show the
    // script section. We won't map the generated render function to this file,
    // because the coverage report would be confusing
    if (scriptFromExternalSrc) {
        return map;
    }

    for (; renderFnStartLine < renderFnEndLine; renderFnStartLine++) {
        map.addMapping({
            source: file,
            generated: {
                line: renderFnStartLine,
                column: 0,
            },
            original: {
                line: templateLine,
                column: 0,
            },
        });
    }

    return map;
};