Coverage map doesn't line up

[lukescott]

I think this may be related to #211 in some way. I put together a transformer (separate from ts-jest) that "works", but the coverage information doesn't line up with the code.

Here is the transformer:

const tsc = require("typescript")
const tsConfig = require("./tsconfig.json") || {}
const babel = require('babel-core')
const jestPreset = require('babel-preset-jest')
const convert = require("convert-source-map");

const createTransformer = (options) => {
	options = Object.assign({}, options, {
		plugins: (options && options.plugins) || [],
		presets: ((options && options.presets) || []).concat([jestPreset]),
		retainLines: true
	});
	delete options.cacheDirectory;
	delete options.filename;

	return {
		canInstrument: true,
		process(src, filename, config, transformOptions) {
			let inputSourceMap
			if (filename.endsWith(".ts") || filename.endsWith(".tsx")) {
				let compilerOptions = Object.assign({},
					tsConfig.compilerOptions, {
						inlineSourceMap: true
						//sourceMap: true
					}
				)
				let transpileOut = tsc.transpileModule(src, {
					fileName: filename,
					compilerOptions
				});
				src = transpileOut.outputText
				inputSourceMap = convert.fromSource(src);
				//inputSourceMap = JSON.parse(transpileOut.sourceMapText)
			}
			const theseOptions = Object.assign({
				filename,
				inputSourceMap,
			}, options);
			if (transformOptions && transformOptions.instrument) {
				theseOptions.auxiliaryCommentBefore = ' istanbul ignore next ';
				// Copied from jest-runtime transform.js
				theseOptions.plugins = theseOptions.plugins.concat([
					[
						require('babel-plugin-istanbul').default, {
							// files outside `cwd` will not be instrumented
							cwd: config.rootDir,
							exclude: []
						}
					]
				]);
			}
			let babelOut = babel.transform(src, theseOptions);
			return babelOut.code;
		}
	};
};

module.exports = createTransformer();
module.exports.createTransformer = createTransformer;

I've tried:

• Every combination I can think of w/ TypeScript + Babel. Fails to line up properly. I am passing the source map from TypeScript into Babel.

• Babel by itself. It lines up correctly.

• TypeScript by itself. It doesn't line up, but also doesn't show highlights.

I'm at a loss at this point. As far as I can tell Babel/Istanbul does not like TypeScript's source maps.

[GeeWee]

What happens if you simply run it through tsc and pass it through babel? If this bug also happens with tsc, I feel like we need to raise this issue in another repro.

[kulshekhar]

@lukescott can you create a minimal repo that reproduces this issue?

[lukescott]

I think it is an issue with babel-plugin-istanbul. I opened an issue here istanbuljs/babel-plugin-istanbul#108. I posted a reproducible repo there. This issue may be relevant to you as ts-jest may suffer from the same problem.

[GeeWee]

Excellent, I'm hoping they will fix it and it's not an issue on our end.

[lukescott]

Ok, so I was able to figure it out. Not sure if this is the final solution, but you need to:

1 - Pass inputSourceMap to babel from typescript (I do that in the code above).
2 - You have to have mapCoverage set to true in your global Jest config, otherwise it won't call transformCoverage, which actually uses the inputSourceMap. Without it inputSourceMap is ignored.

I have no idea why this even an option in Jest. If you're doing a coverage report I would assume this should always be called.

Interestingly enough you have to return .code. If you give Jest the .map it will break again (but differently), even with the above.

[GeeWee]

Huh, that's really strange. Do you know where the switch is inside jest that makes it ignore the inputsourcemap?

[kulshekhar]

It's my understanding that inline sourcemaps work as well