From 02b1bd8bc6d5d783b0cad225881e123375808e02 Mon Sep 17 00:00:00 2001
From: Bruno Ferreira <bmibferreira@gmail.com>
Date: Tue, 9 Aug 2022 02:27:40 +0100
Subject: [PATCH] fix: remove uneeded comparison with condition and simplify
 with new WalkExpressions algorithm

---
 .../terraform_empty_list_equality.go          | 45 ++++++-------------
 .../terraform_empty_list_equality_test.go     |  8 ++--
 2 files changed, 18 insertions(+), 35 deletions(-)

diff --git a/rules/terraformrules/terraform_empty_list_equality.go b/rules/terraformrules/terraform_empty_list_equality.go
index a97545c19..25baf37a3 100644
--- a/rules/terraformrules/terraform_empty_list_equality.go
+++ b/rules/terraformrules/terraform_empty_list_equality.go
@@ -6,6 +6,7 @@ import (
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/hcl/v2/hclsyntax"
 	"github.com/terraform-linters/tflint/tflint"
+	"github.com/zclconf/go-cty/cty"
 )
 
 // TerraformEmptyListEqualityRule checks whether is there a comparison with an empty list
@@ -55,40 +56,22 @@ func (r *TerraformEmptyListEqualityRule) Check(runner *tflint.Runner) error {
 // checkEmptyList visits all blocks that can contain expressions and checks for comparisons with static empty list
 func (r *TerraformEmptyListEqualityRule) checkEmptyList(runner *tflint.Runner) error {
 	return runner.WalkExpressions(func(expr hcl.Expression) error {
-		if conditionalExpr, ok := expr.(*hclsyntax.ConditionalExpr); ok {
-			var issuesRangeSet = make(map[hcl.Range]struct{})
-			r.searchEmptyList(conditionalExpr.Condition, runner, conditionalExpr.Range(), issuesRangeSet)
-			r.emitEmptyListEqualityIssues(issuesRangeSet, runner)
+		if binaryOpExpr, ok := expr.(*hclsyntax.BinaryOpExpr); ok && binaryOpExpr.Op.Type == cty.Bool {
+			if tupleConsExpr, ok := binaryOpExpr.LHS.(*hclsyntax.TupleConsExpr); ok && len(tupleConsExpr.Exprs) == 0 {
+				r.emitEmptyListEqualityIssue(binaryOpExpr.Range(), runner)
+			} else if tupleConsExpr, ok := binaryOpExpr.RHS.(*hclsyntax.TupleConsExpr); ok && len(tupleConsExpr.Exprs) == 0 {
+				r.emitEmptyListEqualityIssue(binaryOpExpr.Range(), runner)
+			}
 		}
 		return nil
 	})
 }
 
-// searchEmptyList Searches for comparisons with static empty list in the given expression
-func (r *TerraformEmptyListEqualityRule) searchEmptyList(expr hcl.Expression, runner *tflint.Runner, exprRange hcl.Range, issuesRangeSet map[hcl.Range]struct{}) {
-	if binaryOpExpr, ok := expr.(*hclsyntax.BinaryOpExpr); ok {
-		if binaryOpExpr.Op.Type.FriendlyName() == "bool" {
-			r.searchEmptyList(binaryOpExpr.RHS, runner, binaryOpExpr.Range(), issuesRangeSet)
-			r.searchEmptyList(binaryOpExpr.LHS, runner, binaryOpExpr.Range(), issuesRangeSet)
-		}
-	} else if binaryOpExpr, ok := expr.(*hclsyntax.BinaryOpExpr); ok {
-		r.searchEmptyList(binaryOpExpr, runner, binaryOpExpr.Range(), issuesRangeSet)
-	} else if parenthesesExpr, ok := expr.(*hclsyntax.ParenthesesExpr); ok {
-		r.searchEmptyList(parenthesesExpr.Expression, runner, parenthesesExpr.Range(), issuesRangeSet)
-	} else if tupleConsExpr, ok := expr.(*hclsyntax.TupleConsExpr); ok {
-		if len(tupleConsExpr.Exprs) == 0 {
-			issuesRangeSet[exprRange] = struct{}{}
-		}
-	}
-}
-
-// emitEmptyListEqualityIssues emits issues for each found comparison with static empty list
-func (r *TerraformEmptyListEqualityRule) emitEmptyListEqualityIssues(exprRanges map[hcl.Range]struct{}, runner *tflint.Runner) {
-	for exprRange := range exprRanges {
-		runner.EmitIssue(
-			r,
-			"Comparing a collection with an empty list is invalid. To detect an empty collection, check its length.",
-			exprRange,
-		)
-	}
+// emitEmptyListEqualityIssue emits issue for comparison with static empty list
+func (r *TerraformEmptyListEqualityRule) emitEmptyListEqualityIssue(exprRange hcl.Range, runner *tflint.Runner) {
+	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
index 8812542f3..484fa4209 100644
--- a/rules/terraformrules/terraform_empty_list_equality_test.go
+++ b/rules/terraformrules/terraform_empty_list_equality_test.go
@@ -45,8 +45,8 @@ resource "aws_db_instance" "mysql" {
 					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: 22},
-						End:      hcl.Pos{Line: 3, Column: 30},
+						Start:    hcl.Pos{Line: 3, Column: 10},
+						End:      hcl.Pos{Line: 3, Column: 18},
 					},
 				},
 				{
@@ -54,8 +54,8 @@ resource "aws_db_instance" "mysql" {
 					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: 10},
-						End:      hcl.Pos{Line: 3, Column: 18},
+						Start:    hcl.Pos{Line: 3, Column: 22},
+						End:      hcl.Pos{Line: 3, Column: 30},
 					},
 				},
 			},