Temporarily ignore key evaluation errors (#200)

Author: wata727

rules/terraform_map_duplicate_keys.go

@@ -80,11 +80,10 @@ func (r *TerraformMapDuplicateKeysRule) checkObjectConsExpr(e hcl.Expression, ru
 		} else {
 			err := runner.EvaluateExpr(expr, &val, nil)
 			if err != nil {
-				diags = append(diags, &hcl.Diagnostic{
-					Severity: hcl.DiagError,
-					Summary:  "failed to evaluate expression",
-					Detail:   err.Error(),
-				})
+				// When a key fails to evaluate, ignore the key and continue processing rather than terminating with an error.
+				// This is due to a limitation that expressions with different scopes, such as for expressions, cannot be evaluated.
+				// @see https://github.com/terraform-linters/tflint-ruleset-terraform/issues/199
+				logger.Debug("Failed to evaluate key. The key will be ignored", "range", expr.Range(), "error", err.Error())
 				continue
 			}
 		}

rules/terraform_map_duplicate_keys_test.go

@@ -193,6 +193,18 @@ resource "null_resource" "test" {
 				},
 			},
 		},
+		{
+			Name: "keys in for expressions",
+			Content: `
+resource "null_resource" "test" {
+  list = [for a in ["foo", "bar"] : {
+    "${a}_baz" = 1
+	"foo_baz" = 2
+  }]
+}`,
+			// The current implementation cannot find duplicate keys in for expressions.
+			Expected: helper.Issues{},
+		},
 	}
 
 	rule := NewTerraformMapDuplicateKeysRule()