Fix NewRunner hook not injecting a custom runner

plugin/host2plugin/host2plugin_test.go

@@ -41,6 +41,7 @@ type mockRuleSetImpl struct {
 	configSchema      func() *hclext.BodySchema
 	applyGlobalConfig func(*tflint.Config) error
 	applyConfig       func(*hclext.BodyContent) error
+	newRunner         func(tflint.Runner) (tflint.Runner, error)
 	check             func(tflint.Runner) error
 }
 
@@ -79,6 +80,13 @@ func (r *mockRuleSet) ApplyConfig(content *hclext.BodyContent) error {
 	return nil
 }
 
+func (r *mockRuleSet) NewRunner(runner tflint.Runner) (tflint.Runner, error) {
+	if r.impl.newRunner != nil {
+		return r.impl.newRunner(runner)
+	}
+	return runner, nil
+}
+
 func (r *mockRuleSet) Check(runner tflint.Runner) error {
 	if r.impl.check != nil {
 		return r.impl.check(runner)
@@ -575,6 +583,14 @@ func (s *mockServer) GetFiles(tflint.ModuleCtxType) map[string][]byte {
 	return map[string][]byte{}
 }
 
+type mockCustomRunner struct {
+	tflint.Runner
+}
+
+func (s *mockCustomRunner) Hello() string {
+	return "Hello from custom runner!"
+}
+
 func TestCheck(t *testing.T) {
 	// default error check helper
 	neverHappend := func(err error) bool { return err != nil }
@@ -589,10 +605,11 @@ func TestCheck(t *testing.T) {
 	}
 
 	tests := []struct {
-		Name       string
-		Arg        func() plugin2host.Server
-		ServerImpl func(tflint.Runner) error
-		ErrCheck   func(error) bool
+		Name          string
+		Arg           func() plugin2host.Server
+		ServerImpl    func(tflint.Runner) error
+		NewRunnerImpl func(tflint.Runner) (tflint.Runner, error)
+		ErrCheck      func(error) bool
 	}{
 		{
 			Name: "bidirectional",
@@ -667,11 +684,26 @@ resource "aws_instance" "foo" {
 				return err == nil || err.Error() != "unexpected error"
 			},
 		},
+		{
+			Name: "inject new runner",
+			Arg: func() plugin2host.Server {
+				return &mockServer{}
+			},
+			NewRunnerImpl: func(runner tflint.Runner) (tflint.Runner, error) {
+				return &mockCustomRunner{runner}, nil
+			},
+			ServerImpl: func(runner tflint.Runner) error {
+				return errors.New(runner.(*mockCustomRunner).Hello())
+			},
+			ErrCheck: func(err error) bool {
+				return err == nil || err.Error() != "Hello from custom runner!"
+			},
+		},
 	}
 
 	for _, test := range tests {
 		t.Run(test.Name, func(t *testing.T) {
-			client := startTestGRPCPluginServer(t, newMockRuleSet("test_ruleset", "0.1.0", mockRuleSetImpl{check: test.ServerImpl}))
+			client := startTestGRPCPluginServer(t, newMockRuleSet("test_ruleset", "0.1.0", mockRuleSetImpl{check: test.ServerImpl, newRunner: test.NewRunnerImpl}))
 
 			err := client.Check(test.Arg())
 			if test.ErrCheck(err) {

plugin/host2plugin/server.go

@@ -116,8 +116,11 @@ func (s *GRPCServer) Check(ctx context.Context, req *proto.Check_Request) (*prot
 	}
 	defer conn.Close()
 
-	err = s.impl.Check(&plugin2host.GRPCClient{Client: proto.NewRunnerClient(conn)})
-
+	runner, err := s.impl.NewRunner(&plugin2host.GRPCClient{Client: proto.NewRunnerClient(conn)})
+	if err != nil {
+		return nil, toproto.Error(codes.FailedPrecondition, err)
+	}
+	err = s.impl.Check(runner)
 	if err != nil {
 		return nil, toproto.Error(codes.Aborted, err)
 	}

tflint/ruleset.go

@@ -106,11 +106,6 @@ func (r *BuiltinRuleSet) NewRunner(runner Runner) (Runner, error) {
 
 // Check runs inspection for each rule by applying Runner.
 func (r *BuiltinRuleSet) Check(runner Runner) error {
-	runner, err := r.NewRunner(runner)
-	if err != nil {
-		return err
-	}
-
 	for _, rule := range r.EnabledRules {
 		if err := rule.Check(runner); err != nil {
 			return fmt.Errorf("Failed to check `%s` rule: %s", rule.Name(), err)