Allow plugins to set host version constraints

go.mod

@@ -7,6 +7,7 @@ require (
 	github.com/google/go-cmp v0.5.9
 	github.com/hashicorp/go-hclog v1.3.0
 	github.com/hashicorp/go-plugin v1.4.5
+	github.com/hashicorp/go-version v1.6.0
 	github.com/hashicorp/hcl/v2 v2.14.0
 	github.com/zclconf/go-cty v1.11.0
 	golang.org/x/tools v0.1.12

go.sum

@@ -41,6 +41,8 @@ github.com/hashicorp/go-hclog v1.3.0 h1:G0ACM8Z2WilWgPv3Vdzwm3V0BQu/kSmrkVtpe1fy
 github.com/hashicorp/go-hclog v1.3.0/go.mod h1:W4Qnvbt70Wk/zYJryRzDRU/4r0kIg0PVHBcfoyhpF5M=
 github.com/hashicorp/go-plugin v1.4.5 h1:oTE/oQR4eghggRg8VY7PAz3dr++VwDNBGCcOfIvHpBo=
 github.com/hashicorp/go-plugin v1.4.5/go.mod h1:viDMjcLJuDui6pXb8U4HVfb8AamCWhHGUjr2IrTF67s=
+github.com/hashicorp/go-version v1.6.0 h1:feTTfFNnjP967rlCxM/I9g701jU+RN74YKx2mOkIeek=
+github.com/hashicorp/go-version v1.6.0/go.mod h1:fltr4n8CU8Ke44wwGCBoEymUuxUHl09ZGVZPK5anwXA=
 github.com/hashicorp/hcl/v2 v2.14.0 h1:jX6+Q38Ly9zaAJlAjnFVyeNSNCKKW8D0wvyg7vij5Wc=
 github.com/hashicorp/hcl/v2 v2.14.0/go.mod h1:e4z5nxYlWNPdDSNYX+ph14EvWYMFm3eP0zIUqPc2jr0=
 github.com/hashicorp/yamux v0.0.0-20180604194846-3520598351bb h1:b5rjCoWHc7eqmAS4/qyk21ZsHyb6Mxv/jykxvNTkU4M=

plugin/fromproto/fromproto.go

@@ -8,6 +8,7 @@ import (
 	"github.com/terraform-linters/tflint-plugin-sdk/hclext"
 	"github.com/terraform-linters/tflint-plugin-sdk/plugin/proto"
 	"github.com/terraform-linters/tflint-plugin-sdk/tflint"
+	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
 
@@ -251,7 +252,12 @@ func Error(err error) error {
 		return err
 	}
 
-	// If the error status has no details, retrieve an error from the gRPC error status.
+	// Unimplemented is an unexpected error, so return as-is.
+	if st.Code() == codes.Unimplemented {
+		return err
+	}
+
+	// If the error status has no details, return an error from the gRPC error status.
 	// Remove the status code because some statuses are expected and should not be shown to users.
 	if len(st.Details()) == 0 {
 		return errors.New(st.Message())

plugin/host2plugin/client.go

@@ -5,6 +5,7 @@ import (
 	"os/exec"
 
 	"github.com/hashicorp/go-plugin"
+	"github.com/hashicorp/go-version"
 	"github.com/terraform-linters/tflint-plugin-sdk/hclext"
 	"github.com/terraform-linters/tflint-plugin-sdk/logger"
 	"github.com/terraform-linters/tflint-plugin-sdk/plugin/fromproto"
@@ -67,6 +68,19 @@ func (c *GRPCClient) RuleNames() ([]string, error) {
 	return resp.Names, nil
 }
 
+// VersionConstraints returns constraints of TFLint versions.
+func (c *GRPCClient) VersionConstraints() (version.Constraints, error) {
+	resp, err := c.client.GetVersionConstraint(context.Background(), &proto.GetVersionConstraint_Request{})
+	if err != nil {
+		return nil, fromproto.Error(err)
+	}
+
+	if resp.Constraint == "" {
+		return version.Constraints{}, nil
+	}
+	return version.NewConstraint(resp.Constraint)
+}
+
 // ConfigSchema fetches the config schema from a plugin.
 func (c *GRPCClient) ConfigSchema() (*hclext.BodySchema, error) {
 	resp, err := c.client.GetConfigSchema(context.Background(), &proto.GetConfigSchema_Request{})

plugin/host2plugin/host2plugin_test.go

@@ -37,6 +37,7 @@ type mockRuleSet struct {
 
 type mockRuleSetImpl struct {
 	ruleNames         func() []string
+	versionConstraint func() string
 	configSchema      func() *hclext.BodySchema
 	applyGlobalConfig func(*tflint.Config) error
 	applyConfig       func(*hclext.BodyContent) error
@@ -50,6 +51,13 @@ func (r *mockRuleSet) RuleNames() []string {
 	return []string{}
 }
 
+func (r *mockRuleSet) VersionConstraint() string {
+	if r.impl.versionConstraint != nil {
+		return r.impl.versionConstraint()
+	}
+	return ""
+}
+
 func (r *mockRuleSet) ConfigSchema() *hclext.BodySchema {
 	if r.impl.configSchema != nil {
 		return r.impl.configSchema()
@@ -192,6 +200,60 @@ func TestRuleNames(t *testing.T) {
 	}
 }
 
+func TestVersionConstraints(t *testing.T) {
+	// default error check helper
+	neverHappend := func(err error) bool { return err != nil }
+
+	tests := []struct {
+		Name       string
+		ServerImpl func() string
+		Want       string
+		ErrCheck   func(error) bool
+	}{
+		{
+			Name: "default",
+			ServerImpl: func() string {
+				return ""
+			},
+			Want:     "",
+			ErrCheck: neverHappend,
+		},
+		{
+			Name: "valid constraint",
+			ServerImpl: func() string {
+				return ">= 1.0"
+			},
+			Want:     ">= 1.0",
+			ErrCheck: neverHappend,
+		},
+		{
+			Name: "invalid constraint",
+			ServerImpl: func() string {
+				return ">> 1.0"
+			},
+			Want: "",
+			ErrCheck: func(err error) bool {
+				return err == nil || err.Error() != "Malformed constraint: >> 1.0"
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Name, func(t *testing.T) {
+			client := startTestGRPCPluginServer(t, newMockRuleSet("test_ruleset", "0.1.0", mockRuleSetImpl{versionConstraint: test.ServerImpl}))
+
+			got, err := client.VersionConstraints()
+			if test.ErrCheck(err) {
+				t.Fatalf("failed to call VersionConstraints: %s", err)
+			}
+
+			if got.String() != test.Want {
+				t.Errorf("want: %s, got: %s", test.Want, got)
+			}
+		})
+	}
+}
+
 func TestConfigSchema(t *testing.T) {
 	// default error check helper
 	neverHappend := func(err error) bool { return err != nil }

plugin/host2plugin/server.go

@@ -63,6 +63,11 @@ func (s *GRPCServer) GetRuleNames(ctx context.Context, req *proto.GetRuleNames_R
 	return &proto.GetRuleNames_Response{Names: s.impl.RuleNames()}, nil
 }
 
+// GetVersionConstraint returns a constraint of TFLint versions.
+func (s *GRPCServer) GetVersionConstraint(ctx context.Context, req *proto.GetVersionConstraint_Request) (*proto.GetVersionConstraint_Response, error) {
+	return &proto.GetVersionConstraint_Response{Constraint: s.impl.VersionConstraint()}, nil
+}
+
 // GetConfigSchema returns the config schema of the plugin.
 func (s *GRPCServer) GetConfigSchema(ctx context.Context, req *proto.GetConfigSchema_Request) (*proto.GetConfigSchema_Response, error) {
 	return &proto.GetConfigSchema_Response{Schema: toproto.BodySchema(s.impl.ConfigSchema())}, nil