fix: improves empty list equality check on conditional expressions

terraform-linters · Jul 1, 2022 · 2095371 · 2095371
1 parent 611a62e
commit 2095371
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Showing 2 changed files with 51 additions and 17 deletions.
diff --git a/rules/terraformrules/terraform_empty_list_equality.go b/rules/terraformrules/terraform_empty_list_equality.go
@@ -55,27 +55,33 @@ func (r *TerraformEmptyListEqualityRule) Check(runner *tflint.Runner) error {
 func (r *TerraformEmptyListEqualityRule) checkEmptyList(runner *tflint.Runner) error {
 	return runner.WalkExpressions(func(expr hcl.Expression) error {
 		if conditionalExpr, ok := expr.(*hclsyntax.ConditionalExpr); ok {
-			if binaryOpExpr, ok := conditionalExpr.Condition.(*hclsyntax.BinaryOpExpr); ok {
-				if binaryOpExpr.Op.Type.FriendlyName() == "bool" {
-					if right, ok := binaryOpExpr.RHS.(*hclsyntax.TupleConsExpr); ok {
-						checkEmptyList(right, runner, r, binaryOpExpr)
-					}
-					if left, ok := binaryOpExpr.LHS.(*hclsyntax.TupleConsExpr); ok {
-						checkEmptyList(left, runner, r, binaryOpExpr)
-					}
-				}
-			}
+			searchEmptyList(conditionalExpr.Condition, runner, r, conditionalExpr.Range())
 		}
 		return nil
 	})
 }
 
-func checkEmptyList(tupleConsExpr *hclsyntax.TupleConsExpr, runner *tflint.Runner, r *TerraformEmptyListEqualityRule, binaryOpExpr *hclsyntax.BinaryOpExpr) {
-	if len(tupleConsExpr.Exprs) == 0 {
-		runner.EmitIssue(
-			r,
-			"Comparing a collection with an empty list is invalid. To detect an empty collection, check its length.",
-			binaryOpExpr.Range(),
-		)
+func searchEmptyList(expr hcl.Expression, runner *tflint.Runner, r *TerraformEmptyListEqualityRule, exprRange hcl.Range) {
+	if binaryOpExpr, ok := expr.(*hclsyntax.BinaryOpExpr); ok {
+		if binaryOpExpr.Op.Type.FriendlyName() == "bool" {
+			searchEmptyList(binaryOpExpr.RHS, runner, r, binaryOpExpr.Range())
+			searchEmptyList(binaryOpExpr.LHS, runner, r, binaryOpExpr.Range())
+		}
+	} else if binaryOpExpr, ok := expr.(*hclsyntax.BinaryOpExpr); ok {
+		searchEmptyList(binaryOpExpr, runner, r, binaryOpExpr.Range())
+	} else if parenthesesExpr, ok := expr.(*hclsyntax.ParenthesesExpr); ok {
+		searchEmptyList(parenthesesExpr.Expression, runner, r, parenthesesExpr.Range())
+	} else if tupleConsExpr, ok := expr.(*hclsyntax.TupleConsExpr); ok {
+		if len(tupleConsExpr.Exprs) == 0 {
+			emitIssue(exprRange, runner, r)
+		}
 	}
 }
+
+func emitIssue(exprRange hcl.Range, runner *tflint.Runner, r *TerraformEmptyListEqualityRule) {
+	runner.EmitIssue(
+		r,
+		"Comparing a collection with an empty list is invalid. To detect an empty collection, check its length.",
+		exprRange,
+	)
+}
diff --git a/rules/terraformrules/terraform_empty_list_equality_test.go b/rules/terraformrules/terraform_empty_list_equality_test.go
@@ -41,6 +41,34 @@ resource "aws_db_instance" "mysql" {
 				},
 			},
 		},
+		{
+			Name: "comparing with [] is not recommended (mixed with other conditions)",
+			Content: `
+resource "aws_db_instance" "mysql" {
+	count = true == true || false != true && (false == false || [] == []) ? 1 : 0
+	instance_class = "m4.2xlarge"
+}`,
+			Expected: tflint.Issues{
+				{
+					Rule:    NewTerraformEmptyListEqualityRule(),
+					Message: "Comparing a collection with an empty list is invalid. To detect an empty collection, check its length.",
+					Range: hcl.Range{
+						Filename: "resource.tf",
+						Start:    hcl.Pos{Line: 3, Column: 62},
+						End:      hcl.Pos{Line: 3, Column: 70},
+					},
+				},
+				{
+					Rule:    NewTerraformEmptyListEqualityRule(),
+					Message: "Comparing a collection with an empty list is invalid. To detect an empty collection, check its length.",
+					Range: hcl.Range{
+						Filename: "resource.tf",
+						Start:    hcl.Pos{Line: 3, Column: 62},
+						End:      hcl.Pos{Line: 3, Column: 70},
+					},
+				},
+			},
+		},
 		{
 			Name: "negatively comparing with [] is not recommended",
 			Content: `