Regex path matching issue

[pimterry]

Hello,

I was looking at allowing different RegEx patterns in the url matching. RegEx test cases

I see in the test cases you only run tests with direct regex expressions and not strings. await server.get(/.*.txt/).thenReply(200, 'Fake file');

Tried to create a regex pattern via new RegExp("some regex pattern string") but I am having match issues.

const regExPattern = new RegExp(regExPatternString, 'g');
await server.get(regExPattern).thenReply(200, 'Fake file');

Any tips ?

Originally posted by @chrisribe in https://github.com/httptoolkit/mockttp/issues/9#issuecomment-1158910337

[pimterry]

Hi @chrisribe! I've just moved this to a separate issue since the previous one was resolved.

Yes, if you want to use regexes you do need to provide a real regex object. Any strings passed to .get(x) will be matched exactly, not as a regex pattern.

Your example looks correct though. Can you share some specific patterns that aren't working for you, and the requests that they're failing to match?

[chrisribe]

Thanks for the reply and new issue for this :)

My example test case that does not match properly. url to match https://www.w3schools.com/lib/my-learning.js?v=1.0.9

Code that does not match

server.forGet(/(.*)w3schools.com\/lib\/my-learning.js(.*)9$/)
      .thenReply(200, 'There is a match !');

[pimterry]

That I can explain easily: forGet() matches against the path specifically, not the query string, so the 9 never matches anything.

If you want to match against the query string, you need do so explicitly, for example:

server.forGet(/(.*)w3schools.com\/lib\/my-learning.js/)
      // Either:
      .withExactQuery('?v=1.0.9')
      // Or:
      .withQuery({ v: '1.0.9' })
      .thenReply(200, 'There is a match !');

Does that make sense?

I can see how this is a bit surprising, especially since we include the rest of the base domain here nowadays. It's tricky to change backward compatibly though, and for non-regex cases with exact string you generally do want matching to work like this... I'll keep an eye on that and see if I can improve this in a future major version bump.

[chrisribe]

Ah that would explain it !

Yes this is very surprising as I was expecting that passing a regex would simply match on that for the full url. So another regex that fails for me, and this fails because of the Query check at ? /(.*)w3schools.com\/lib\/my-learning.js\?v=(.*)9/

Any way to regex match on the full url and not use .withExactQuery or .withQuery ?

Like if I want to match on certain query parameter patterns ?v=1.(.*).9 RegexPathMatcher ?

[chrisribe]

I did find this showing all query param matchers do not support RegEx at all :(

query-matching.spec.ts

[pimterry]

Yes, it's not possible to do query matching by regex right now. PRs very welcome though! It should be fairly easy to add a withQueryMatching(/regex/) matcher that would do what you want.

Alternatively, it might make sense to extend withQuery({ v: '1.0.0' }) to allow withQuery({ v: /1.0.[0-9]/ }), so you can provide regexes to match against individual query values, independent of the order.

If you're interested in adding that, I'd suggest starting by writing a couple of tests for it, then exploring the existing matcher definition implementations you can find defined around here: https://github.com/httptoolkit/mockttp/blob/0d586c5336a659f788a6d65b4bf6d979b3cc29ae/src/rules/base-rule-builder.ts#L136-L144.