provider/terraform: remote state resource becomes a data source

As a first example of a real-world data source, the pre-existing
terraform_remote_state resource is adapted to be a data source. The
original resource is shimmed to wrap the data source for backward
compatibility.

builtin/providers/terraform/data_source_state.go

@@ -8,23 +8,19 @@ import (
 	"github.com/hashicorp/terraform/state/remote"
 )
 
-func resourceRemoteState() *schema.Resource {
+func dataSourceRemoteState() *schema.Resource {
 	return &schema.Resource{
-		Create: resourceRemoteStateCreate,
-		Read:   resourceRemoteStateRead,
-		Delete: resourceRemoteStateDelete,
+		Read: dataSourceRemoteStateRead,
 
 		Schema: map[string]*schema.Schema{
 			"backend": &schema.Schema{
 				Type:     schema.TypeString,
 				Required: true,
-				ForceNew: true,
 			},
 
 			"config": &schema.Schema{
 				Type:     schema.TypeMap,
 				Optional: true,
-				ForceNew: true,
 			},
 
 			"output": &schema.Schema{
@@ -35,11 +31,7 @@ func resourceRemoteState() *schema.Resource {
 	}
 }
 
-func resourceRemoteStateCreate(d *schema.ResourceData, meta interface{}) error {
-	return resourceRemoteStateRead(d, meta)
-}
-
-func resourceRemoteStateRead(d *schema.ResourceData, meta interface{}) error {
+func dataSourceRemoteStateRead(d *schema.ResourceData, meta interface{}) error {
 	backend := d.Get("backend").(string)
 	config := make(map[string]string)
 	for k, v := range d.Get("config").(map[string]interface{}) {
@@ -69,8 +61,3 @@ func resourceRemoteStateRead(d *schema.ResourceData, meta interface{}) error {
 	d.Set("output", outputs)
 	return nil
 }
-
-func resourceRemoteStateDelete(d *schema.ResourceData, meta interface{}) error {
-	d.SetId("")
-	return nil
-}

builtin/providers/terraform/provider.go

@@ -9,7 +9,12 @@ import (
 func Provider() terraform.ResourceProvider {
 	return &schema.Provider{
 		ResourcesMap: map[string]*schema.Resource{
-			"terraform_remote_state": resourceRemoteState(),
+			"terraform_remote_state": schema.DataSourceResourceShim(
+				dataSourceRemoteState(),
+			),
+		},
+		DataSourcesMap: map[string]*schema.Resource{
+			"terraform_remote_state": dataSourceRemoteState(),
 		},
 	}
 }

website/source/docs/providers/terraform/d/remote_state.html.md

@@ -1,7 +1,7 @@
 ---
 layout: "terraform"
 page_title: "Terraform: terraform_remote_state"
-sidebar_current: "docs-terraform-resource-remote-state"
+sidebar_current: "docs-terraform-datasource-remote-state"
 description: |-
   Accesses state meta data from a remote backend.
 ---
@@ -13,7 +13,7 @@ Retrieves state meta data from a remote backend
 ## Example Usage
 
 ```
-resource "terraform_remote_state" "vpc" {
+data "terraform_remote_state" "vpc" {
     backend = "atlas"
     config {
         name = "hashicorp/vpc-prod"
@@ -22,7 +22,7 @@ resource "terraform_remote_state" "vpc" {
 
 resource "aws_instance" "foo" {
     # ...
-    subnet_id = "${terraform_remote_state.vpc.output.subnet_id}"
+    subnet_id = "${data.terraform_remote_state.vpc.output.subnet_id}"
 }
 ```
 

website/source/docs/providers/terraform/index.html.markdown

@@ -8,23 +8,16 @@ description: |-
 
 # Terraform Provider
 
-The terraform provider exposes resources to access state meta data
-for Terraform outputs from shared infrastructure.
+The terraform provider provides access to outputs from the Terraform state
+of shared infrastructure.
 
-The terraform provider is what we call a _logical provider_. This has no
-impact on how it behaves, but conceptually it is important to understand.
-The terraform provider doesn't manage any _physical_ resources; it isn't
-creating servers, writing files, etc. It is used to access the outputs
-of other Terraform states to be used as inputs for resources.
-Examples will explain this best.
-
-Use the navigation to the left to read about the available resources.
+Use the navigation to the left to read about the available data sources.
 
 ## Example Usage
 
 ```
 # Shared infrastructure state stored in Atlas
-resource "terraform_remote_state" "vpc" {
+data "terraform_remote_state" "vpc" {
     backend = "atlas"
     config {
         path = "hashicorp/vpc-prod"
@@ -33,6 +26,6 @@ resource "terraform_remote_state" "vpc" {
 
 resource "aws_instance" "foo" {
     # ...
-    subnet_id = "${terraform_remote_state.vpc.output.subnet_id}"
+    subnet_id = "${data.terraform_remote_state.vpc.output.subnet_id}"
 }
 ```

website/source/layouts/terraform.erb

@@ -10,11 +10,11 @@
 					<a href="/docs/providers/terraform/index.html">Terraform Provider</a>
 				</li>
 
-				<li<%= sidebar_current(/^docs-terraform-resource/) %>>
-					<a href="#">Resources</a>
+				<li<%= sidebar_current(/^docs-terraform-datasource/) %>>
+					<a href="#">Data Sources</a>
 					<ul class="nav nav-visible">
-						<li<%= sidebar_current("docs-terraform-resource-remote-state") %>>
-							<a href="/docs/providers/terraform/r/remote_state.html">terraform_remote_state</a>
+						<li<%= sidebar_current("docs-terraform-datasource-remote-state") %>>
+							<a href="/docs/providers/terraform/d/remote_state.html">terraform_remote_state</a>
 						</li>
 					</ul>
 				</li>