Add Fir generation support to heroku_app data source (#415)

- Add generation field to schema and read function
- Update documentation to support both Cedar and Fir apps
- Add test coverage for Fir app data source behavior
- Remove classic buildpacks limitation from docs

Resolves: W-19773193

Update docs/data-sources/app.md




Update docs/data-sources/app.md

Signed-off-by: Johnny Winn <[email protected]>
Co-authored-by: Sandy Lai <[email protected]>

Author: heroku-johnny

docs/data-sources/app.md

@@ -10,14 +10,23 @@ description: |-
 
 Use this data source to get information about a Heroku app.
 
-~> **NOTE:** This resource is only supported for apps that use [classic buildpacks](https://devcenter.heroku.com/articles/buildpacks#classic-buildpacks).
+This data source supports both the [Cedar and Fir generations](https://devcenter.heroku.com/articles/generations) of Heroku apps.
 
 ## Example Usage
 
 ```hcl-terraform
 # Lookup an existing Heroku app
 data "heroku_app" "default" {
-  name   = "my-cool-app"
+  name = "my-cool-app"
+}
+
+# Example: Check app generation and buildpacks
+output "app_generation" {
+  value = data.heroku_app.default.generation
+}
+
+output "app_buildpacks" {
+  value = data.heroku_app.default.buildpacks
 }
 ```
 
@@ -39,7 +48,9 @@ The following attributes are exported:
 
 * `stack`: The application [stack](https://devcenter.heroku.com/articles/stack) is what platform to run the application in.
 
-* `buildpacks`: A list of buildpacks that this app uses.
+* `generation`: The generation of the app platform (`cedar` or `fir`).
+
+* `buildpacks`: The list of buildpacks that this app uses. Empty for apps using Cloud Native Buildpacks, such as Fir-generation apps, which list buildpacks in `project.toml` instead.
 
 * `space`: The [space](https://devcenter.heroku.com/articles/private-spaces) in which the app runs. Not present for [Common Runtime](https://devcenter.heroku.com/articles/dyno-runtime#common-runtime) apps.
 

heroku/data_source_heroku_app.go

@@ -35,6 +35,12 @@ func dataSourceHerokuApp() *schema.Resource {
 				Default:  nil,
 			},
 
+			"generation": {
+				Type:        schema.TypeString,
+				Computed:    true,
+				Description: "Generation of the app platform (cedar or fir)",
+			},
+
 			"internal_routing": {
 				Type:     schema.TypeBool,
 				Computed: true,
@@ -139,6 +145,7 @@ func dataSourceHerokuAppRead(d *schema.ResourceData, m interface{}) error {
 
 	d.Set("buildpacks", app.Buildpacks)
 	d.Set("config_vars", app.Vars)
+	d.Set("generation", app.Generation)
 
 	releaseRange := heroku.ListRange{
 		Field:      "version",
@@ -147,7 +154,7 @@ func dataSourceHerokuAppRead(d *schema.ResourceData, m interface{}) error {
 	}
 	releases, err := client.ReleaseList(context.Background(), app.App.ID, &releaseRange)
 	if err != nil {
-		return fmt.Errorf("Failed to fetch releases for app '%s': %s", name, err)
+		return fmt.Errorf("failed to fetch releases for app '%s': %s", name, err)
 	}
 	for _, r := range releases {
 		if r.Status == "succeeded" {

heroku/data_source_heroku_app_test.go

@@ -34,6 +34,8 @@ func TestAccDatasourceHerokuApp_Basic(t *testing.T) {
 						"data.heroku_app.foobar", "buildpacks.0", "https://github.com/heroku/heroku-buildpack-multi-procfile"),
 					resource.TestCheckResourceAttr(
 						"data.heroku_app.foobar", "acm", "false"),
+					resource.TestCheckResourceAttr(
+						"data.heroku_app.foobar", "generation", "cedar"),
 				),
 			},
 		},
@@ -89,6 +91,41 @@ func TestAccDatasourceHerokuApp_Organization(t *testing.T) {
 	})
 }
 
+// testStep_AccDatasourceHerokuApp_Generation_Fir tests the data source with a Fir app
+func testStep_AccDatasourceHerokuApp_Generation_Fir(t *testing.T, spaceConfig, spaceName string) resource.TestStep {
+	randString := acctest.RandString(5)
+	appName := fmt.Sprintf("tftest-app-ds-fir-%s", randString)
+
+	config := fmt.Sprintf(`%s
+
+resource "heroku_app" "data_source_test" {
+  name   = "%s"
+  region = heroku_space.foobar.region
+  space  = heroku_space.foobar.name
+  
+  organization {
+    name = "%s"
+  }
+}
+
+data "heroku_app" "data_source_test" {
+  name = heroku_app.data_source_test.name
+}`,
+		spaceConfig, appName, testAccConfig.GetOrganizationOrSkip(t))
+
+	return resource.TestStep{
+		Config: config,
+		Check: resource.ComposeTestCheckFunc(
+			resource.TestCheckResourceAttr("data.heroku_app.data_source_test", "name", appName),
+			resource.TestCheckResourceAttr("data.heroku_app.data_source_test", "generation", "fir"),
+			resource.TestCheckResourceAttr("data.heroku_app.data_source_test", "stack", "cnb"),
+			resource.TestCheckResourceAttr("data.heroku_app.data_source_test", "buildpacks.#", "0"),
+			resource.TestCheckResourceAttrSet("data.heroku_app.data_source_test", "id"),
+			resource.TestCheckResourceAttrSet("data.heroku_app.data_source_test", "space"),
+		),
+	}
+}
+
 func testAccCheckHerokuApp_basic(appName string) string {
 	return fmt.Sprintf(`
 resource "heroku_app" "foobar" {

heroku/resource_heroku_space_test.go

@@ -88,7 +88,9 @@ func TestAccHerokuSpace_Fir(t *testing.T) {
 			testStep_AccHerokuApp_Generation_Fir(t, spaceConfig, spaceName),
 			// Step 3: Test Fir build generation behavior (valid build)
 			testStep_AccHerokuBuild_Generation_FirValid(spaceConfig, spaceName),
-			// Step 4: Test Fir telemetry drain functionality
+			// Step 4: Test Fir app data source functionality
+			testStep_AccDatasourceHerokuApp_Generation_Fir(t, spaceConfig, spaceName),
+			// Step 5: Test Fir telemetry drain functionality
 			testStep_AccHerokuTelemetryDrain_Generation_Fir(t, spaceConfig, spaceName),
 		},
 	})