feat: Ensure example matches regex when creating a term

[thompsnm]

I noticed that the Term matcher does not verify that the example matches the regular expression. For example, the following was considered valid:

matchers.Term("notanumber", `\d+`)

This creates the potential for a consumer to write tests against an example value in the mock provider that does not match what the provider actually returns, causing a breakdown in the assurances the Pact ecosystem is meant to provide. I updated the Term function to verify the regex is valid and that the example matches the regex. In doing so, I discovered that two of the sugar regexes defined in the matcher.go file were not valid regular expressions in Go. I took a first pass at updating them to make them valid.

[thompsnm]

It appears that Go’s regexp engine does not support Perl-style negative lookaheads: (?!. When running the test suite against the existing regular expressions using the newly added regex validation, I got the following error:

=== RUN   TestMatcher_SugarMatchers
--- FAIL: TestMatcher_SugarMatchers (0.00s)
panic: Term: invalid regex "^([\\+-]?\\d{4}(?!\\d{2}\\b))((-?)((0[1-9]|1[0-2])(\\3([12]\\d|0[1-9]|3[01]))?|W([0-4]\\d|5[0-2])(-?[1-7])?|(00[1-9]|0[1-9]\\d|[12]\\d{2}|3([0-5]\\d|6[1-6])))?)": error parsing regexp: invalid or unsupported Perl syntax: `(?!` [recovered]
        panic: Term: invalid regex "^([\\+-]?\\d{4}(?!\\d{2}\\b))((-?)((0[1-9]|1[0-2])(\\3([12]\\d|0[1-9]|3[01]))?|W([0-4]\\d|5[0-2])(-?[1-7])?|(00[1-9]|0[1-9]\\d|[12]\\d{2}|3([0-5]\\d|6[1-6])))?)": error parsing regexp: invalid or unsupported Perl syntax: `(?!`

goroutine 38 [running]:
testing.tRunner.func1.2({0x104eb5980, 0xc00002b410})
        /usr/local/go/src/testing/testing.go:1734 +0x2bc
testing.tRunner.func1()
        /usr/local/go/src/testing/testing.go:1737 +0x47c
panic({0x104eb5980?, 0xc00002b410?})
        /usr/local/go/src/runtime/panic.go:792 +0x124
github.com/pact-foundation/pact-go/v2/matchers.Term({0xc00000fcb6, 0xa}, {0x104e33f99, 0x96})
        /Users/nathan/Development/pact-go/matchers/matcher.go:118 +0x2a0
github.com/pact-foundation/pact-go/v2/matchers.Date()
        /Users/nathan/Development/pact-go/matchers/matcher.go:161 +0xe4
github.com/pact-foundation/pact-go/v2/matchers.TestMatcher_SugarMatchers(0xc00016d880)
        /Users/nathan/Development/pact-go/matchers/matcher_test.go:472 +0x8b4
testing.tRunner(0xc00016d880, 0x104f0f158)
        /usr/local/go/src/testing/testing.go:1792 +0x184
created by testing.(*T).Run in goroutine 1
        /usr/local/go/src/testing/testing.go:1851 +0x688
FAIL    github.com/pact-foundation/pact-go/v2/matchers  0.279s
FAIL
make: *** [test] Error 1

[YOU54F]

Thanks for the change, looks good from a cursory review, have tagged Matt as well for review and set CI off :)

[coveralls]

coverage: 28.283% (+0.05%) from 28.238%
when pulling e49be00 on thompsnm:verify-term-example-against-regex
into 6057b94 on pact-foundation:master.

[mefellows]

Thanks. Go doesn't evaluate those regexes - they're evaluated in the core matching engine. This is likely why the issue is only appearing once you also apply the check. I think the change is reasonable, but probably makes more sense to be in the core so all languages get the same benefit (in fact, I thought that was the behaviour of the core already).

The regex appears to be a looser version of the current one, so I don't think it will break existing clients that may upgrade to a version that includes this.

Please correct me if I'm wrong.