Add PasswordChecker exercise for Result concept

[blackk-foxx]

See the relevant forum discussion for context.

• Add required infrastructure files
• Add concept doc
• Add exercise instructions

[github-actions]

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[blackk-foxx]

I believe this version achieves the mutual goals of teaching the Result concept in a focused manner and having only a minimal set of prerequisites.

One drawback I see with this exercise is that it expects only a single rule violation for any given input, whereas any real-world password checker would be able to indicate when a combination of rules is violated. A related concern is the "magic" precedence of rules. For example, if a given password is of sufficient length, but violates all the other rules, then the tests expect specifically the AtLeastOneUppercaseLetter rule. If it meets the AtLeastOneUppercaseLetter rule but violates all the others, then the tests expect specifically Error AtLeastOneLowercaseLetter.

Maybe there could be a follow-up concept exercise for Flags enums that could extend the PasswordChecker to report multiple rule violations at a time.

[SleeplessByte]

cc @ErikSchierboom

[ErikSchierboom]

I believe this version achieves the mutual goals of teaching the Result concept in a focused manner and having only a minimal set of prerequisites.

Totally agree. This looks great.

Maybe there could be a follow-up concept exercise for Flags enums that could extend the PasswordChecker to report multiple rule violations at a time.

That is exactly what I was thinking of! Love that.

[blackk-foxx]

A related concern is the "magic" precedence of rules. For example, if a given password is of sufficient length, but violates all the other rules, then the tests expect specifically the AtLeastOneUppercaseLetter rule. If it meets the AtLeastOneUppercaseLetter rule but violates all the others, then the tests expect specifically Error AtLeastOneLowercaseLetter.

I think I eliminated this problem by narrowing the tests to test only a single rule violation at a time.

[blackk-foxx]

I am guessing that the doc check is failing on this line (but it is hard to tell since the error message does not indicate a line number). Any suggestions on how to remedy this? I could add a function body like failwith "Not implemented" but I fear that would be a distraction. Ideally, I would like to exclude line 57 from the doc check.