fix: Allow remote state to be used with Terraform (#1242)

The Terraform Provisioner depended on the statefile content
being at a specific path, which disallowed the use of external
state providers. This fixes it!

provisioner/terraform/provision.go

@@ -53,13 +53,6 @@ func (t *terraform) Provision(stream proto.DRPCProvisioner_ProvisionStream) erro
 		}
 	}()
 	start := request.GetStart()
-	statefilePath := filepath.Join(start.Directory, "terraform.tfstate")
-	if len(start.State) > 0 {
-		err := os.WriteFile(statefilePath, start.State, 0600)
-		if err != nil {
-			return xerrors.Errorf("write statefile %q: %w", statefilePath, err)
-		}
-	}
 
 	terraform, err := tfexec.NewTerraform(start.Directory, t.binaryPath)
 	if err != nil {
@@ -246,14 +239,18 @@ func (t *terraform) Provision(stream proto.DRPCProvisioner_ProvisionStream) erro
 		errorMessage := err.Error()
 		// Terraform can fail and apply and still need to store it's state.
 		// In this case, we return Complete with an explicit error message.
-		statefileContent, err := os.ReadFile(statefilePath)
+		state, err := terraform.Show(stream.Context())
 		if err != nil {
-			return xerrors.Errorf("read file %q: %w", statefilePath, err)
+			return xerrors.Errorf("show state: %w", err)
+		}
+		stateData, err := json.Marshal(state)
+		if err != nil {
+			return xerrors.Errorf("marshal state: %w", err)
 		}
 		return stream.Send(&proto.Provision_Response{
 			Type: &proto.Provision_Response_Complete{
 				Complete: &proto.Provision_Complete{
-					State: statefileContent,
+					State: stateData,
 					Error: errorMessage,
 				},
 			},
@@ -266,7 +263,7 @@ func (t *terraform) Provision(stream proto.DRPCProvisioner_ProvisionStream) erro
 	if start.DryRun {
 		resp, err = parseTerraformPlan(stream.Context(), terraform, planfilePath)
 	} else {
-		resp, err = parseTerraformApply(stream.Context(), terraform, statefilePath)
+		resp, err = parseTerraformApply(stream.Context(), terraform)
 	}
 	if err != nil {
 		return err
@@ -366,14 +363,10 @@ func parseTerraformPlan(ctx context.Context, terraform *tfexec.Terraform, planfi
 	}, nil
 }
 
-func parseTerraformApply(ctx context.Context, terraform *tfexec.Terraform, statefilePath string) (*proto.Provision_Response, error) {
-	statefileContent, err := os.ReadFile(statefilePath)
+func parseTerraformApply(ctx context.Context, terraform *tfexec.Terraform) (*proto.Provision_Response, error) {
+	state, err := terraform.Show(ctx)
 	if err != nil {
-		return nil, xerrors.Errorf("read file %q: %w", statefilePath, err)
-	}
-	state, err := terraform.ShowStateFile(ctx, statefilePath)
-	if err != nil {
-		return nil, xerrors.Errorf("show state file %q: %w", statefilePath, err)
+		return nil, xerrors.Errorf("show state file: %w", err)
 	}
 	resources := make([]*proto.Resource, 0)
 	if state.Values != nil {
@@ -508,6 +501,11 @@ func parseTerraformApply(ctx context.Context, terraform *tfexec.Terraform, state
 		}
 	}
 
+	statefileContent, err := json.Marshal(state)
+	if err != nil {
+		return nil, xerrors.Errorf("marshal state: %w", err)
+	}
+
 	return &proto.Provision_Response{
 		Type: &proto.Provision_Response_Complete{
 			Complete: &proto.Provision_Complete{

provisioner/terraform/provision_test.go

@@ -91,7 +91,13 @@ provider "coder" {
 			"main.tf": `variable "A" {
 			}`,
 		},
-		Error: true,
+		Response: &proto.Provision_Response{
+			Type: &proto.Provision_Response_Complete{
+				Complete: &proto.Provision_Complete{
+					Error: "exit status 1",
+				},
+			},
+		},
 	}, {
 		Name: "single-resource",
 		Files: map[string]string{
@@ -499,6 +505,8 @@ provider "coder" {
 				resourcesWant, err := json.Marshal(testCase.Response.GetComplete().Resources)
 				require.NoError(t, err)
 
+				require.Equal(t, testCase.Response.GetComplete().Error, msg.GetComplete().Error)
+
 				require.Equal(t, string(resourcesWant), string(resourcesGot))
 				break
 			}