mruby-regexp: let mrbtest exercise Symbol#[] with a regexp - #7060

mrbgems/mruby-regexp/test/symbol_regexp.rb asserts the regexp form of Symbol#[],
guarded like this:

assert("Symbol#[] with regexp") do
  skip unless :hello.respond_to?(:slice)

The guard is always false under rake test, so the assertion never runs.

mrbtest runs each gem's tests in a state of its own: mrbgems/mruby-test/mrbgem.rake
opens an mrb_open_core() state per gem and initialises it with tsort_dependencies([g.name]),
that gem's declared dependency closure and nothing else. mruby-regexp declares
mruby-string-ext (and mruby-enumerator when the build already has it), while
Symbol#[] and Symbol#slice come from mruby-symbol-ext
(mrbgems/mruby-symbol-ext/mrblib/symbol.rb:72, aliased as [] on line 76). So the run
reports:

Skip: Symbol#[] with regexp (mrbgems: mruby-regexp)

and the sym[re] path that the gem README lists among the supported Symbol methods has no
coverage in CI. The other assertions in the file do run: Symbol#match, #match? and #=~
are defined by this gem itself, so they are present in that state.

Nothing is broken

The feature works in a build that has both gems, which is every default.gembox build,
since stdlib.gembox pulls in mruby-regexp and mruby-symbol-ext:

$ ./build/host/bin/mruby -e 'p :hello[/l+/], :hello.slice(/(?<x>l+)/, :x), :hello[/z/]'
"ll"
"ll"
nil

The test is correct as written, and it is skipped for a structural reason rather than a
defect.

The change

mrbgems/mruby-regexp/mrbgem.rake already has the pattern for this, added for
mruby-enumerator: depend on a gem only when the build has it anyway, so that mrbtest
sees it without dragging it into builds that do not want it.

  if build.gems.any? {|g| g.name == 'mruby-symbol-ext'}
    spec.add_dependency 'mruby-symbol-ext', :core => 'mruby-symbol-ext'
  end

The skip guard stays: it is what keeps the test honest in a build that leaves
mruby-symbol-ext out.

Verification

rake test on this branch: the assertion runs and passes, and the skip count drops from
19 to 18 with no failures (Total 1987, OK 1969, KO 0).

One wrinkle when reproducing it: the generated per-gem test wrapper does not depend on the
gem's mrbgem.rake, so an incremental build keeps reporting the old result until the gem's
test files are touched or the build directory is cleaned.

Summary by CodeRabbit

• Tests
  • Expanded regexp-related test coverage for symbol slicing features when the optional symbol extension is available.