test/formula_installer_spec: add tests for cyclic deps

Library/Homebrew/test/formula_installer_spec.rb

@@ -96,8 +96,64 @@ describe FormulaInstaller do
     end
   end
 
-  specify "check installation sanity pinned dependency" do
-    dep_name = "dependency"
+  describe "#check_install_sanity" do
+    it "raises on direct cyclic dependency" do
+      ENV["HOMEBREW_DEVELOPER"] = "1"
+
+      dep_name = "homebrew-test-cyclic"
+      dep_path = CoreTap.new.formula_dir/"#{dep_name}.rb"
+      dep_path.write <<~RUBY
+        class #{Formulary.class_s(dep_name)} < Formula
+          url "foo"
+          version "0.1"
+          depends_on "#{dep_name}"
+        end
+      RUBY
+      Formulary.cache.delete(dep_path)
+      f = Formulary.factory(dep_name)
+
+      fi = described_class.new(f)
+
+      expect {
+        fi.check_install_sanity
+      }.to raise_error(CannotInstallFormulaError)
+    end
+
+    it "raises on indirect cyclic dependency" do
+      ENV["HOMEBREW_DEVELOPER"] = "1"
+
+      formula1_name = "homebrew-test-formula1"
+      formula2_name = "homebrew-test-formula2"
+      formula1_path = CoreTap.new.formula_dir/"#{formula1_name}.rb"
+      formula1_path.write <<~RUBY
+        class #{Formulary.class_s(formula1_name)} < Formula
+          url "foo"
+          version "0.1"
+          depends_on "#{formula2_name}"
+        end
+      RUBY
+      Formulary.cache.delete(formula1_path)
+      formula1 = Formulary.factory(formula1_name)
+
+      formula2_path = CoreTap.new.formula_dir/"#{formula2_name}.rb"
+      formula2_path.write <<~RUBY
+        class #{Formulary.class_s(formula2_name)} < Formula
+          url "foo"
+          version "0.1"
+          depends_on "#{formula1_name}"
+        end
+      RUBY
+      Formulary.cache.delete(formula2_path)
+
+      fi = described_class.new(formula1)
+
+      expect {
+        fi.check_install_sanity
+      }.to raise_error(CannotInstallFormulaError)
+    end
+
+    it "raises on pinned dependency" do
+      dep_name = "homebrew-test-dependency"
       dep_path = CoreTap.new.formula_dir/"#{dep_name}.rb"
       dep_path.write <<~RUBY
         class #{Formulary.class_s(dep_name)} < Formula
@@ -131,6 +187,7 @@ describe FormulaInstaller do
         fi.check_install_sanity
       }.to raise_error(CannotInstallFormulaError)
     end
+  end
 
   specify "install fails with BuildError when a system() call fails" do
     ENV["HOMEBREW_TEST_NO_EXIT_CLEANUP"] = "1"