mruby-test: regenerate the per-gem test wrapper when a mrbgem.rake it is generated from changes - #7160

Problem

The per-gem test wrapper build/<target>/mrbgems/<gem>/gem_test.c is generated from mrbgem.rake, not only from the test files it embeds. Its body follows the gem's spec.test_rbfiles, spec.test_preload, spec.test_args and spec.test_objs (via custom_test_init?), and it declares and calls the init/final function of every gem returned by tsort_dependencies.

The file task that generates it, however, listed only the test .rb files and mrbc as prerequisites:

file g.test_rbireps => [g.test_rbfiles, build.mrbcfile].flatten do |t|

So editing a mrbgem.rake does not invalidate the wrapper. An incremental rake test keeps running the previously generated test set and reporting the previous result, until a test file happens to be touched or the build directory is cleaned. This is easy to mistake for a test that legitimately still passes (or still fails), which makes it an actively misleading failure mode when adding, removing or re-scoping a gem's tests.

Reproduction

On a fully built tree (rake test:build), narrow one gem's test set without touching any test file. Append to mrbgems/mruby-string-ext/mrbgem.rake:

spec.test_rbfiles = ["#{MRUBY_ROOT}/mrbgems/mruby-string-ext/test/string.rb"]

Then rebuild:

$ rake test:build
$ ./build/host/bin/mrbtest | grep Total:
  Total: 2049

gem_test.c is byte-identical to before the edit and still embeds all three ireps; the count is unchanged. touch mrbgems/mruby-string-ext/test/string.rb && rake test:build then produces the expected single-irep wrapper and Total: 2044, confirming the stale artifact is the wrapper itself.

(Note that plain rake will not show this: the mruby-test gem is only loaded under the test:build task.)

Fix

Add to the wrapper's prerequisites the mrbgem.rake of the gem and of each gem in its dependency list, plus mruby-test/mrbgem.rake itself, which holds the generator.

Tracking the dependency list is not defensive; it is load-bearing. Adding spec.add_dependency 'mruby-math', core: 'mruby-math' to mrbgems/mruby-string-ext/mrbgem.rake changes the wrapper of mruby-regexp, which depends on it, because mruby-math's init/final calls are emitted there too. Tracking only the gem's own rakefile leaves that wrapper stale.

Both dependencies follow existing convention in the tree: MRuby::Command::Compiler#define_rules already records mrbgem.rake for a gem's C objects, and the sibling mrbtest.c rule already records __FILE__ for its own generator. The per-gem test wrapper was simply missing both. The change is in mrbtest's rake rules only. No gem or core source is touched, and nothing is specific to any one gem.

The File.exist? filter keeps the rule safe for a MRuby::Gem::Specification that is not backed by an on-disk mrbgem.rake: a prerequisite that neither exists nor has a rule would abort the build. define_rules guards the same way.

One input remains untracked and is left for a separate change: the contents of the file named by spec.test_preload are embedded in the wrapper, but only its path is covered here. No in-tree gem currently sets test_preload.

Verification

• Narrowing a gem's test set via mrbgem.rake alone, with no test file touched and test/string.rb older than the existing gem_test.c, now regenerates the wrapper and moves the count from Total: 2049 to Total: 2044; reverting the edit restores Total: 2049.
• The cross-gem case above regenerates mruby-regexp's wrapper from bb189b91… to 4c6a7f5f…, with grep -c GENERATED_TMP_mrb_mruby_math_gem_init going from 0 to 2, the same content reached by force-touching that gem's own rakefile.
• touch mrbgems/mruby-test/mrbgem.rake && rake test:build regenerates all 50 wrappers, where previously it regenerated none.
• A cold build (rake clean, then full build) generates all wrappers and yields the same totals as before.

rake -m test on the current master with this change: Total: 2075, OK: 2046, KO: 0, Crash: 0, Warning: 0, Skip: 29, plus bintest Total: 105, KO: 0, Crash: 0. No behavioural change to the tests themselves is expected; this only makes an incremental build notice inputs it was already using.

Summary by CodeRabbit

• Bug Fixes

  • Improved test build reliability by ensuring generated test artifacts are refreshed when gem configuration or test dependencies change.
  • Preserved existing dependency-based test wrapper generation behavior.

• Chores

  • Updated test generation dependency tracking to reduce stale or outdated test results.