Include eval coverage in the strict profile

The strict profile pins line, branch, and method coverage at 100%, but
left eval coverage off. On Ruby 3.2+, code reached through Kernel#eval
(notably ERB templates whose ERB#filename= has been set) gets routed
through the standard line and branch counters, so leaving the toggle
off meant strict was quietly lenient on the exact code paths most
likely to grow untested.

The profile now flips `enable_coverage :eval` on when the runtime
supports it. The guard avoids the "Coverage for eval is not available"
warning that would otherwise fire every time the profile loaded on
Ruby 3.1 (the project's minimum), keeping graceful degradation
consistent with how the existing branch and method clauses no-op on
JRuby. A new spec asserts the toggle matches `coverage_for_eval_supported?`
on whichever runtime the suite is running on, and the README's
"equivalent" example mirrors the new conditional.

Author: sferik

README.md

@@ -970,12 +970,15 @@ That's equivalent to writing out:
 SimpleCov.start do
   enable_coverage :branch
   enable_coverage :method
+  enable_coverage :eval if Coverage.respond_to?(:supported?) && Coverage.supported?(:eval)
   minimum_coverage line: 100, branch: 100, method: 100
 end
 ```
 
 The profile drops the branch / method clauses on engines that don't support those criteria (JRuby), so it still
-loads cleanly there — just enforcing line coverage at 100%.
+loads cleanly there — just enforcing line coverage at 100%. `:eval` is included on Ruby 3.2+ (where the runtime
+supports it), so any code reached through `Kernel#eval` — typically ERB templates with `ERB#filename=` set — is
+held to the same 100% bar. On older Rubies, the `:eval` clause is silently skipped.
 
 ### Custom profiles
 

lib/simplecov/profiles/strict.rb

@@ -14,8 +14,19 @@
 # materialize. `CoverageViolations` skips threshold lookups for
 # criteria not in the stats, so the `:branch` / `:method` clauses below
 # silently no-op on JRuby and only `:line` is enforced.
+#
+# `:eval` widens the universe of code held to 100% to include strings
+# passed through `Kernel#eval` (typically ERB templates, when the user
+# sets `ERB#filename=`). Guarded on `coverage_for_eval_supported?` so
+# the profile stays quiet on Ruby < 3.2, where `enable_coverage :eval`
+# would otherwise warn about the missing runtime support every time
+# the profile loads.
 SimpleCov.profiles.define "strict" do
   enable_coverage :branch
   enable_coverage :method
+  # simplecov:disable branch — dogfood runs on Ruby >= 3.2 only, so
+  # the else arm (eval coverage not supported) is unreachable from CI.
+  enable_coverage :eval if coverage_for_eval_supported?
+  # simplecov:enable
   minimum_coverage line: 100, branch: 100, method: 100
 end

spec/profiles_spec.rb

@@ -29,11 +29,13 @@
     around do |example|
       prev_criteria = SimpleCov.coverage_criteria.dup
       prev_min      = SimpleCov.minimum_coverage.dup
+      prev_eval     = SimpleCov.instance_variable_get(:@coverage_for_eval_enabled)
       example.run
     ensure
       SimpleCov.clear_coverage_criteria
       prev_criteria.each { |c| SimpleCov.enable_coverage(c) }
       SimpleCov.minimum_coverage(prev_min.empty? ? {} : prev_min)
+      SimpleCov.instance_variable_set(:@coverage_for_eval_enabled, prev_eval)
     end
 
     # No engine-conditional logic in the profile itself — every clause
@@ -47,5 +49,17 @@
       expect(SimpleCov.coverage_criteria).to include(:line, :branch, :method)
       expect(SimpleCov.minimum_coverage).to eq(line: 100, branch: 100, method: 100)
     end
+
+    # `:eval` widens the strict universe to include code passed through
+    # `Kernel#eval` (ERB templates, etc.) on runtimes that support it.
+    # On older Rubies the toggle is silently skipped — `enable_coverage
+    # :eval` would otherwise warn about missing runtime support every
+    # time the profile loaded.
+    it "enables :eval when the runtime supports it" do
+      SimpleCov.instance_variable_set(:@coverage_for_eval_enabled, false)
+      SimpleCov.load_profile "strict"
+
+      expect(SimpleCov.coverage_for_eval_enabled?).to eq(SimpleCov.coverage_for_eval_supported?)
+    end
   end
 end