@nx/eslint plugin - add option to write results to a file and pretty-print to console

[jeremyhofer]

Context

As part of running our tasks in CI via Nx Cloud we have the desire to not only pretty print the lint results in the console for devs to read / triage / fix issues, but also to save results to a file for external analysis of applied lint rules, configured overrides, ignores, etc. for tech-debt tracking and investment.

Relevant executor logic:

nx/packages/eslint/src/executors/lint/lint.impl.ts

Lines 182 to 195 in 2a0d89d

	const formatter = await eslint.loadFormatter(normalizedOptions.format);
	const formattedResults = await formatter.format(lintResults);
	if (normalizedOptions.outputFile) {
	const pathToOutputFile = joinPathFragments(
	context.root,
	normalizedOptions.outputFile
	);
	mkdirSync(dirname(pathToOutputFile), { recursive: true });
	writeFileSync(pathToOutputFile, formattedResults);
	} else {
	console.info(formattedResults);
	}

Current State

Today the @nx/eslint lint executor allows for the format of the output to be specified and an outputFile to save the output in to be specified. See docs for specifics: https://nx.dev/nx-api/eslint/executors/lint

Desired State

I would like to be able to configure the lint executor to write to an outputFile with a given format (e.g. json) while also outputting to the console with a given format (e.g. the default stylish format).

Considering the formats available, it may be helpful to allow configuring multiple different output file formats as part of a single lint execution, such as writing a json file for programmatic consumption and a html file for a more user-friendly and accessible view than CLI text output.

Considered Approaches

Different Targets

I considered adding a separate e.g. lint-with-output-file target onto our projects in order to allow for us to run a lint target that pretty prints to the console, as is BAU today, and have this other target that would output data in json format to a file.

The issue with this approach is that it would require running eslint twice per-project, as the lint results of the lint would be cached based on the target, not the actual lint invocation. Ideally eslint itself would only have to be executed once, and its results output in different formats as desired.

Output a json file and post-process into other forms

The json formatter for eslint simply writes the eslint output (which is already json) to a file. Given this a custom executor that wraps the @nx/eslint lint executor could be developed to orchestrate the logic around running eslint, generating the json output, then post-processing it into other formats and outputting to additional files as necessary.

This approach is very flexible, but this could easily be integrated with the existing lint executor instead of requiring Nx users to introduce custom executors and custom logic to solve this.