Add support for path.* named values

docs/guides/compatibility.md

@@ -13,7 +13,15 @@ Like Terraform, it supports the `--var`,` --var-file` options, automatic loading
 
 ## Named Values
 
-[Named values](https://www.terraform.io/docs/configuration/expressions.html#references-to-named-values) are supported only for [input variables](https://www.terraform.io/docs/configuration/variables.html) and [workspaces](https://www.terraform.io/docs/state/workspaces.html). Expressions that contain anything else are excluded from the  inspection.
+[Named values](https://www.terraform.io/docs/configuration/expressions.html#references-to-named-values) are supported partially. The following named values are available:
+
+- `var.<NAME>`
+- `path.module`
+- `path.root`
+- `path.cwd`
+- `terraform.workspace`
+
+Expressions that reference named values not included above are excluded from the inspection.
 
 ## Built-in Functions
 

tflint/runner.go

@@ -543,6 +543,8 @@ func isEvaluable(expr hcl.Expression) bool {
 			// noop
 		case addrs.TerraformAttr:
 			// noop
+		case addrs.PathAttr:
+			// noop
 		default:
 			return false
 		}

tflint/runner_test.go

@@ -19,6 +19,12 @@ import (
 )
 
 func Test_EvaluateExpr_string(t *testing.T) {
+	dir, err := ioutil.TempDir("", "string")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
 	cases := []struct {
 		Name     string
 		Content  string
@@ -144,14 +150,24 @@ resource "null_resource" "test" {
 }`,
 			Expected: "Hello World",
 		},
+		{
+			Name: "path.root",
+			Content: `
+resource "null_resource" "test" {
+  key = path.root
+}`,
+			Expected: filepath.ToSlash(dir),
+		},
+		{
+			Name: "path.module",
+			Content: `
+resource "null_resource" "test" {
+  key = path.module
+}`,
+			Expected: filepath.ToSlash(dir),
+		},
 	}
 
-	dir, err := ioutil.TempDir("", "string")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(dir)
-
 	for _, tc := range cases {
 		err := ioutil.WriteFile(dir+"/resource.tf", []byte(tc.Content), os.ModePerm)
 		if err != nil {
@@ -184,6 +200,53 @@ resource "null_resource" "test" {
 	}
 }
 
+func Test_EvaluateExpr_pathCwd(t *testing.T) {
+	dir, err := ioutil.TempDir("", "string")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	content := `
+resource "null_resource" "test" {
+  key = path.cwd
+}`
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := filepath.ToSlash(cwd)
+
+	err = ioutil.WriteFile(dir+"/resource.tf", []byte(content), os.ModePerm)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cfg, err := loadConfigHelper(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	attribute, err := extractAttributeHelper("key", cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	runner, err := NewRunner(EmptyConfig(), map[string]Annotations{}, cfg, map[string]*terraform.InputValue{})
+	if err != nil {
+		t.Fatalf("Unexpected error: %s", err)
+	}
+
+	var ret string
+	err = runner.EvaluateExpr(attribute.Expr, &ret)
+	if err != nil {
+		t.Fatalf("Unexpected error: `%s`", err)
+	}
+
+	if expected != ret {
+		t.Fatalf("expected value is `%s`, but get `%s`", expected, ret)
+	}
+}
+
 func Test_EvaluateExpr_integer(t *testing.T) {
 	cases := []struct {
 		Name     string
@@ -833,6 +896,14 @@ resource "null_resource" "test" {
 }`,
 			Expected: false,
 		},
+		{
+			Name: "path attributes",
+			Content: `
+resource "null_resource" "test" {
+	key = path.cwd
+}`,
+			Expected: true,
+		},
 	}
 
 	dir, err := ioutil.TempDir("", "isEvaluable")