port-name-suffix: handle ref direction and all-underscore names

[EylonKrause]

Problem

PortNameSuffixRule crashes the linter on two kinds of valid SystemVerilog:

1. A ref port direction throws std::out_of_range (uncaught → linter abort).
2. An all-underscore port name (e.g. _) dereferences an empty vector (UB).

Details

1. ref direction — IsSuffixCorrect does suffixes.at(direction), where suffixes only has keys {input, output, inout}. The grammar's port_direction : dir | TK_ref allows ref, so a port like module m(ref logic data_x); endmodule reaches suffixes.at("ref"), which throws. HandleSymbol runs without a surrounding try/catch, so the linter terminates. (The comment claiming the direction "is guaranteed" to be a known key is incorrect.)

2. all-underscore name — name_parts = absl::StrSplit(name, '_', absl::SkipEmpty()). For a name that is only underscores (_, __), every token is empty and SkipEmpty drops them all, leaving name_parts empty. The if (name_parts.size() < 2) block reports a violation but does not return, so name_parts.back() on the next line dereferences an empty vector (UB).

Fix

1. Look the direction up with find() and treat an unknown direction (e.g. ref) as "correct" — no violation — matching Violation(), which already ignores non-input/output/inout directions.
2. return after the size() < 2 violation (a name with fewer than two underscore-delimited parts has no suffix to check). This also removes a redundant duplicate Violation insert for no-underscore names.

Tests

port-name-suffix-rule_test.cc: a ref port is accepted (no violation, no crash); an all-underscore _ port reports a single suffix violation instead of crashing.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: EylonKrause / name: Eylon Krause (94d48b9)

[EylonKrause]

Disclosure: this contribution was authored with an AI coding assistant (Claude) and reviewed before submission.

[hzeller]

We have the FindWithDefault() in verible/common/util/container-util.h

Maybe use that instead, not only for a more compact writing but also a more visible 'we're looking for something that might not be there but we have a fallback' intent.

return FindWithDefault(suffixes, direction, 1) == 1;

[hzeller]

Thanks for your contribution!
LGTM, but I have one comment about using a map lookup function that might be nicer in this case.

[EylonKrause]

Thanks! Done — switched to FindWithDefault. Since suffixes maps each direction to a set of valid suffixes (rather than a scalar), I used it with an empty-set fallback so the "look for something that might not be there, with a fallback" intent is explicit, while keeping the behavior that a direction with no convention (e.g. ref) is treated as correct:

static const std::set<std::string_view> kNoConvention;
const std::set<std::string_view> &valid =
    verible::container::FindWithDefault(suffixes, direction, kNoConvention);
return valid.empty() || valid.count(suffix) == 1;