Add terraform.applying symbol

Follow up of hashicorp/terraform@7c928fc

terraform/evaluator.go

@@ -1,3 +1,6 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: BUSL-1.1
+
 package terraform
 
 import (
@@ -301,6 +304,10 @@ func (d *evaluationData) GetTerraformAttr(addr addrs.TerraformAttr, rng hcl.Rang
 		workspaceName := d.Meta.Env
 		return cty.StringVal(workspaceName), diags
 
+	case "applying":
+		// terraform.applying always returns false in TFLint
+		return cty.BoolVal(false).Mark(marks.Ephemeral), nil
+
 	case "env":
 		// Prior to Terraform 0.12 there was an attribute "env", which was
 		// an alias name for "workspace". This was deprecated and is now

terraform/evaluator_test.go

@@ -170,6 +170,13 @@ variable "string_var" {
 			want:     `cty.StringVal("default")`,
 			errCheck: neverHappend,
 		},
+		{
+			name:     "terraform.applying",
+			expr:     expr(`terraform.applying`),
+			ty:       cty.Bool,
+			want:     `cty.False.Mark(marks.Ephemeral)`,
+			errCheck: neverHappend,
+		},
 		{
 			name: "interpolation in string",
 			config: `