Merge pull request #377 from hashicorp/f-path-var

Add ${path.X} variables for path referencing

config/config.go

@@ -201,17 +201,22 @@ func (c *Config) Validate() error {
 
 	// Check that all count variables are valid.
 	for source, vs := range vars {
-		for _, v := range vs {
-			cv, ok := v.(*CountVariable)
-			if !ok {
-				continue
-			}
-
-			if cv.Type == CountValueInvalid {
+		for _, rawV := range vs {
+			switch v := rawV.(type) {
+			case *CountVariable:
+				if v.Type == CountValueInvalid {
 					errs = append(errs, fmt.Errorf(
 						"%s: invalid count variable: %s",
 						source,
-					cv.FullKey()))
+						v.FullKey()))
+				}
+			case *PathVariable:
+				if v.Type == PathValueInvalid {
+					errs = append(errs, fmt.Errorf(
+						"%s: invalid path variable: %s",
+						source,
+						v.FullKey()))
+				}
 			}
 		}
 	}

config/config_test.go

@@ -144,6 +144,20 @@ func TestConfigValidate_outputBadField(t *testing.T) {
 	}
 }
 
+func TestConfigValidate_pathVar(t *testing.T) {
+	c := testConfig(t, "validate-path-var")
+	if err := c.Validate(); err != nil {
+		t.Fatal("err: %s", err)
+	}
+}
+
+func TestConfigValidate_pathVarInvalid(t *testing.T) {
+	c := testConfig(t, "validate-path-var-invalid")
+	if err := c.Validate(); err == nil {
+		t.Fatal("should not be valid")
+	}
+}
+
 func TestConfigValidate_unknownThing(t *testing.T) {
 	c := testConfig(t, "validate-unknownthing")
 	if err := c.Validate(); err == nil {

config/interpolate.go

@@ -75,6 +75,22 @@ type ModuleVariable struct {
 	key   string
 }
 
+// A PathVariable is a variable that references path information about the
+// module.
+type PathVariable struct {
+	Type PathValueType
+	key  string
+}
+
+type PathValueType byte
+
+const (
+	PathValueInvalid PathValueType = iota
+	PathValueCwd
+	PathValueModule
+	PathValueRoot
+)
+
 // A ResourceVariable is a variable that is referencing the field
 // of a resource, such as "${aws_instance.foo.ami}"
 type ResourceVariable struct {
@@ -101,6 +117,8 @@ type UserVariable struct {
 func NewInterpolatedVariable(v string) (InterpolatedVariable, error) {
 	if strings.HasPrefix(v, "count.") {
 		return NewCountVariable(v)
+	} else if strings.HasPrefix(v, "path.") {
+		return NewPathVariable(v)
 	} else if strings.HasPrefix(v, "var.") {
 		return NewUserVariable(v)
 	} else if strings.HasPrefix(v, "module.") {
@@ -206,6 +224,28 @@ func (v *ModuleVariable) FullKey() string {
 	return v.key
 }
 
+func NewPathVariable(key string) (*PathVariable, error) {
+	var fieldType PathValueType
+	parts := strings.SplitN(key, ".", 2)
+	switch parts[1] {
+	case "cwd":
+		fieldType = PathValueCwd
+	case "module":
+		fieldType = PathValueModule
+	case "root":
+		fieldType = PathValueRoot
+	}
+
+	return &PathVariable{
+		Type: fieldType,
+		key:  key,
+	}, nil
+}
+
+func (v *PathVariable) FullKey() string {
+	return v.key
+}
+
 func NewResourceVariable(key string) (*ResourceVariable, error) {
 	parts := strings.SplitN(key, ".", 3)
 	if len(parts) < 3 {

config/interpolate_test.go

@@ -45,6 +45,14 @@ func TestNewInterpolatedVariable(t *testing.T) {
 			},
 			false,
 		},
+		{
+			"path.module",
+			&PathVariable{
+				Type: PathValueModule,
+				key:  "path.module",
+			},
+			false,
+		},
 	}
 
 	for i, tc := range cases {

config/module/test-fixtures/child/foo/bar/main.tf

@@ -0,0 +1,2 @@
+# Hello
+

config/module/test-fixtures/child/foo/main.tf

@@ -0,0 +1,5 @@
+# Hello
+
+module "bar" {
+    source = "./bar"
+}

config/module/test-fixtures/child/main.tf

@@ -0,0 +1,5 @@
+# Hello
+
+module "foo" {
+    source = "./foo"
+}

config/module/tree.go

@@ -67,6 +67,20 @@ func (t *Tree) Config() *config.Config {
 	return t.config
 }
 
+// Child returns the child with the given path (by name).
+func (t *Tree) Child(path []string) *Tree {
+	if len(path) == 0 {
+		return t
+	}
+
+	c := t.Children()[path[0]]
+	if c == nil {
+		return nil
+	}
+
+	return c.Child(path[1:])
+}
+
 // Children returns the children of this tree (the modules that are
 // imported by this root).
 //

config/module/tree_test.go

@@ -6,6 +6,42 @@ import (
 	"testing"
 )
 
+func TestTreeChild(t *testing.T) {
+	storage := testStorage(t)
+	tree := NewTree("", testConfig(t, "child"))
+	if err := tree.Load(storage, GetModeGet); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Should be able to get the root child
+	if c := tree.Child([]string{}); c == nil {
+		t.Fatal("should not be nil")
+	} else if c.Name() != "root" {
+		t.Fatalf("bad: %#v", c.Name())
+	}
+
+	// Should be able to get the root child
+	if c := tree.Child(nil); c == nil {
+		t.Fatal("should not be nil")
+	} else if c.Name() != "root" {
+		t.Fatalf("bad: %#v", c.Name())
+	}
+
+	// Should be able to get the foo child
+	if c := tree.Child([]string{"foo"}); c == nil {
+		t.Fatal("should not be nil")
+	} else if c.Name() != "foo" {
+		t.Fatalf("bad: %#v", c.Name())
+	}
+
+	// Should be able to get the nested child
+	if c := tree.Child([]string{"foo", "bar"}); c == nil {
+		t.Fatal("should not be nil")
+	} else if c.Name() != "bar" {
+		t.Fatalf("bad: %#v", c.Name())
+	}
+}
+
 func TestTreeLoad(t *testing.T) {
 	storage := testStorage(t)
 	tree := NewTree("", testConfig(t, "basic"))

config/test-fixtures/validate-path-var-invalid/main.tf

@@ -0,0 +1,3 @@
+resource "aws_instance" "foo" {
+    foo = "${path.nope}"
+}

config/test-fixtures/validate-path-var/main.tf

@@ -0,0 +1,3 @@
+resource "aws_instance" "foo" {
+    foo = "${path.module}"
+}

terraform/context.go

@@ -3,6 +3,7 @@ package terraform
 import (
 	"fmt"
 	"log"
+	"os"
 	"sort"
 	"strconv"
 	"strings"
@@ -1437,6 +1438,24 @@ func (c *walkContext) computeVars(
 			}
 
 			vs[n] = value
+		case *config.PathVariable:
+			switch v.Type {
+			case config.PathValueCwd:
+				wd, err := os.Getwd()
+				if err != nil {
+					return fmt.Errorf(
+						"Couldn't get cwd for var %s: %s",
+						v.FullKey(), err)
+				}
+
+				vs[n] = wd
+			case config.PathValueModule:
+				if t := c.Context.module.Child(c.Path[1:]); t != nil {
+					vs[n] = t.Config().Dir
+				}
+			case config.PathValueRoot:
+				vs[n] = c.Context.module.Config().Dir
+			}
 		case *config.ResourceVariable:
 			var attr string
 			var err error

terraform/context_test.go

@@ -2,6 +2,7 @@ package terraform
 
 import (
 	"fmt"
+	"os"
 	"reflect"
 	"sort"
 	"strings"
@@ -2822,6 +2823,43 @@ func TestContextPlan_moduleDestroy(t *testing.T) {
 	}
 }
 
+func TestContextPlan_pathVar(t *testing.T) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	m := testModule(t, "plan-path-var")
+	p := testProvider("aws")
+	p.DiffFn = testDiffFn
+	ctx := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	plan, err := ctx.Plan(nil)
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	actual := strings.TrimSpace(plan.String())
+	expected := strings.TrimSpace(testTerraformPlanPathVarStr)
+
+	// Warning: this ordering REALLY matters for this test. The
+	// order is: cwd, module, root.
+	expected = fmt.Sprintf(
+		expected,
+		cwd,
+		m.Config().Dir,
+		m.Config().Dir)
+
+	if actual != expected {
+		t.Fatalf("bad:\n%s\n\nexpected:\n\n%s", actual, expected)
+	}
+}
+
 func TestContextPlan_diffVar(t *testing.T) {
 	m := testModule(t, "plan-diffvar")
 	p := testProvider("aws")

terraform/terraform_test.go

@@ -875,3 +875,18 @@ STATE:
 
 <no state>
 `
+
+const testTerraformPlanPathVarStr = `
+DIFF:
+
+CREATE: aws_instance.foo
+  cwd:    "" => "%s/barpath"
+  module: "" => "%s/foopath"
+  root:   "" => "%s/barpath"
+  type:   "" => "aws_instance"
+
+STATE:
+
+<no state>
+`
+

terraform/test-fixtures/plan-path-var/main.tf

@@ -0,0 +1,5 @@
+resource "aws_instance" "foo" {
+    cwd = "${path.cwd}/barpath"
+    module = "${path.module}/foopath"
+    root = "${path.root}/barpath"
+}

website/source/docs/configuration/interpolation.html.md

@@ -39,6 +39,12 @@ For example, `${count.index}` will interpolate the current index
 in a multi-count resource. For more information on count, see the
 resource configuration page.
 
+**To reference path information**, the syntax is `path.TYPE`.
+TYPE can be `cwd`, `module`, or `root`. `cwd` will interpolate the
+cwd. `module` will interpolate the path to the current module. `root`
+will interpolate the path of the root module. In general, you probably
+want the `path.module` variable.
+
 ## Built-in Functions
 
 Terraform ships with built-in functions. Functions are called with

website/source/docs/modules/create.html.markdown

@@ -79,6 +79,32 @@ And that is all there is to it. Variables and outputs are used to configure
 modules and provide results. Resources within a module are isolated,
 and the whole thing is managed as a single unit.
 
+## Paths and Embedded Files
+
+It is sometimes useful to embed files within the module that aren't
+Terraform configuration files, such as a script to provision a resource
+or a file to upload.
+
+In these cases, you can't use a relative path, since paths in Terraform
+are generally relative to the working directory that Terraform was executed
+from. Instead, you want to use a module-relative path. To do this, use
+the [path interpolated variables](/docs/configuration/interpolation.html).
+
+An example is shown below:
+
+```
+resource "aws_instance" "server" {
+	...
+
+	provisioner "remote-exec" {
+		script = "${path.module}/script.sh"
+	}
+}
+```
+
+In the above, we use `${path.module}` to get a module-relative path. This
+is usually what you'll want in any case.
+
 ## Nested Modules
 
 You can use a module within a module just like you would anywhere else.