RuleTester - Add "debug" flag for valid/invalid code

The problem you want to solve. While writing a custom rule, I found myself wanting to debug my rule but only for a specific code block. I was able to do this by commenting out all of the others - but then I was unable to see the status of those tests as I tweaked my custom rule for the code that I was interested in debugging. Once I had the rule working as expected for the code I was debugging, I uncommented the others and realized that some were broken.

It would be nice if there was a flag that I could pass into a specific code config that would enable a conditional breakpoint so that I could step into my custom rule for that code.

Your take on the correct solution to problem. I was thinking update the config for code to accept a “debug” flag, that would wrap the rule in an anonymous function with a debugger at the top.

// config accepts a "debug" flag that would enable a conditional debugger during testing of the code block
ruleTester.run("no-var", require("../../fixtures/testers/rule-tester/no-var"), {
    valid: [],
    invalid: [{
        code: "var foo = bar || baz",
        debug: true
    }],
});

// and then somewhere inside of RuleTester/linter the rule would be wrapped like so
function debuggedRule() {
    debugger;
    rule.apply(this, arguments);
}

// somewhere else 😅
var ruleToRun = config.debug ? debuggedRule : rule;
callRuleWithAstParsedSourceCode(ruleToRun, astParsedSourceCode)

Also as a best practice, I was thinking to automatically trigger a test failure if any of the rules have a “debug: true” flag - this way a debugger would hopefully not sneak into “live” code.

Are you willing to submit a pull request to implement this change? Yes - I can attempt to make a minimal set of changes. I have not really considered or understand how we might want to differentiate between wanting to debug the custom rule code vs the auto-fixing of the rule.

[mdjermanovic]

Can we tweak this to make it something like adding the debugger by the user itself instead of conditionally calling the function that is having the debugger?

Just an idea, maybe something like before function that would be called before running the rule on the test code:

ruleTester.run("no-var", require("../../fixtures/testers/rule-tester/no-var"), {
    valid: [],
    invalid: [{
        code: "var foo = bar || baz",
        before() { debugger; }
    }],
});

[anikethsaha]

Thanks for the issue.

I have faced the similar issue multiple times. Rule tester is a public API and IMO, shipping debugger in public API maybe not be a good move. Can we tweak this to make it something like adding the debugger by the user itself instead of conditionally calling the function that is having the debugger?