GemfileLockResolver adjusted to exclude all specs when runtime dependencies are empty (#208)

- regression test: Ruby library projects with no runtime dependencies do not include development dependencies

Author: pboling

pkg/deps/ruby.go

@@ -70,12 +70,11 @@ func (r *GemfileLockResolver) Resolve(lockfile string, config *ConfigDeps, repor
 		if err != nil {
 			return err
 		}
-		if len(runtimeRoots) == 0 {
-			// Fallback: if not found, use DEPENDENCIES from lockfile
-			roots = deps
-		} else {
-			roots = runtimeRoots
-		}
+		// Use only runtime dependencies from gemspec(s);
+		// Do not fallback to DEPENDENCIES
+		// A gem library inherits runtime dependencies ONLY from the gemspec.
+		// All other dependencies are development only.
+		roots = runtimeRoots
 	} else {
 		// App: all declared dependencies are relevant
 		roots = deps
@@ -84,7 +83,7 @@ func (r *GemfileLockResolver) Resolve(lockfile string, config *ConfigDeps, repor
 	// Compute the set of included gems
 	include := reachable(specs, roots)
 	// For app without explicit deps (rare), include all specs
-	if len(roots) == 0 {
+	if !isLibrary && len(roots) == 0 {
 		for name := range specs {
 			include[name] = struct{}{}
 		}

pkg/deps/ruby_test.go

@@ -187,3 +187,58 @@ func TestRubyMissingSpecIsSkippedGracefully(t *testing.T) {
 		t.Fatalf("expected missing_gem to be marked as skipped")
 	}
 }
+
+func TestRubyLibraryWithNoRuntimeDependenciesIncludesNone(t *testing.T) {
+	resolver := new(GemfileLockResolver)
+
+	// Prepare a library project with a gemspec that has NO runtime dependencies
+	dir := t.TempDir()
+	lockContent := "" +
+		"GEM\n" +
+		"  remote: https://rubygems.org/\n" +
+		"  specs:\n" +
+		"    rake (13.0.6)\n" +
+		"    rspec (3.10.0)\n" +
+		"      rspec-core (~> 3.10)\n" +
+		"    rspec-core (3.10.1)\n" +
+		"\n" +
+		"PLATFORMS\n" +
+		"  ruby\n" +
+		"\n" +
+		"DEPENDENCIES\n" +
+		"  rake\n" +
+		"  rspec\n" +
+		"\n" +
+		"BUNDLED WITH\n" +
+		"   2.4.10\n"
+	if err := writeFileRuby(filepath.Join(dir, "Gemfile.lock"), lockContent); err != nil {
+		t.Fatal(err)
+	}
+
+	gemspec := "" +
+		"# minimal gemspec without runtime dependencies\n" +
+		"Gem::Specification.new do |spec|\n" +
+		"  spec.name          = \"sample\"\n" +
+		"  spec.version       = \"0.1.0\"\n" +
+		"  spec.summary       = \"Sample gem\"\n" +
+		"  spec.description   = \"Sample\"\n" +
+		"  spec.authors       = [\"Test\"]\n" +
+		"  spec.files         = []\n" +
+		"  # only development dependency present\n" +
+		"  spec.add_development_dependency 'rspec', '~> 3.10'\n" +
+		"end\n"
+	if err := writeFileRuby(filepath.Join(dir, "sample.gemspec"), gemspec); err != nil {
+		t.Fatal(err)
+	}
+
+	lock := filepath.Join(dir, "Gemfile.lock")
+	cfg := &ConfigDeps{Files: []string{lock}}
+	report := Report{}
+	if err := resolver.Resolve(lock, cfg, &report); err != nil {
+		t.Fatal(err)
+	}
+
+	if got := len(report.Resolved) + len(report.Skipped); got != 0 {
+		t.Fatalf("expected 0 dependencies for library with no runtime deps, got %d", got)
+	}
+}