terraform_unused_required_providers: handle module provider overrides

rules/terraformrules/terraform_unused_required_providers.go

@@ -71,6 +71,14 @@ func (r *TerraformUnusedRequiredProvidersRule) checkProvider(runner *tflint.Runn
 		}
 	}
 
+	for _, module := range runner.TFConfig.Module.ModuleCalls {
+		for _, provider := range module.Providers {
+			if provider.InParent.Name == required.Name {
+				return
+			}
+		}
+	}
+
 	runner.EmitIssue(
 		r,
 		fmt.Sprintf("provider '%s' is declared in required_providers but not used by the module", required.Name),

rules/terraformrules/terraform_unused_required_providers_test.go

@@ -82,6 +82,49 @@ func Test_TerraformUnusedRequiredProvidersRule(t *testing.T) {
 			`,
 			Expected: tflint.Issues{},
 		},
+		{
+			Name: "used - module provider override",
+			Content: `
+				terraform {
+					required_providers {
+						custom-null = {
+							source = "custom/null"
+						}
+					}
+				}
+
+				module "m" {
+					source = "./m"
+
+					providers = {
+						null = custom-null
+					}
+				}
+			`,
+			Expected: tflint.Issues{},
+		},
+		{
+			Name: "used - module provider override with alias",
+			Content: `
+				terraform {
+					required_providers {
+						null = {
+							source = "hashicorp/null"
+							configuration_aliases = [null.a]
+						}
+					}
+				}
+
+				module "m" {
+					source = "./m"
+
+					providers = {
+						null = null.a
+					}
+				}
+			`,
+			Expected: tflint.Issues{},
+		},
 		{
 			Name: "used - provider",
 			Content: `
@@ -163,6 +206,39 @@ func Test_TerraformUnusedRequiredProvidersRule(t *testing.T) {
 				},
 			},
 		},
+		{
+			Name: "unused - module",
+			Content: `
+				terraform {
+					required_providers {
+						null = {
+							source = "hashicorp/null"
+						}
+					}
+				}
+
+				module "m" {
+					source = "./m"
+				}
+			`,
+			Expected: tflint.Issues{
+				{
+					Rule:    NewTerraformUnusedRequiredProvidersRule(),
+					Message: "provider 'null' is declared in required_providers but not used by the module",
+					Range: hcl.Range{
+						Filename: "module.tf",
+						Start: hcl.Pos{
+							Line:   4,
+							Column: 14,
+						},
+						End: hcl.Pos{
+							Line:   6,
+							Column: 8,
+						},
+					},
+				},
+			},
+		},
 	}
 
 	rule := NewTerraformUnusedRequiredProvidersRule()