packer: allow specifying channel in packer_image

A hcp_packer_image used to rely on the iteration_id, which it could get
from a second resource in the plan.

However, this information is redundant, as the image's ID can be
inferred directly by the image block, if we specify its channel.

Therefore, we let a user specify either an iteration_id for
compatibility, or a channel so they won't need both information in a
single plan.

docs/data-sources/packer_image.md

@@ -38,11 +38,12 @@ output "packer-registry-ubuntu" {
 
 - `bucket_name` (String) The slug of the HCP Packer Registry image bucket to pull from.
 - `cloud_provider` (String) Name of the cloud provider this image is stored-in.
-- `iteration_id` (String) HCP ID of this image.
 - `region` (String) Region this image is stored in, if any.
 
 ### Optional
 
+- `channel` (String) Channel that promotes the latest iteration of the image. Either this or `iteration_id` must be specified.
+- `iteration_id` (String) HCP ID of this image. Either this or `channel' must be specified.
 - `timeouts` (Block, Optional) (see [below for nested schema](#nestedblock--timeouts))
 
 ### Read-Only

internal/provider/data_source_packer_image.go

@@ -2,9 +2,11 @@ package provider
 
 import (
 	"context"
+	"fmt"
 	"log"
 	"time"
 
+	packermodels "github.com/hashicorp/hcp-sdk-go/clients/cloud-packer-service/stable/2021-04-30/models"
 	sharedmodels "github.com/hashicorp/hcp-sdk-go/clients/cloud-shared/v1/models"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
@@ -33,16 +35,24 @@ func dataSourcePackerImage() *schema.Resource {
 				Type:        schema.TypeString,
 				Required:    true,
 			},
-			"iteration_id": {
-				Description: "HCP ID of this image.",
-				Type:        schema.TypeString,
-				Required:    true,
-			},
 			"region": {
 				Description: "Region this image is stored in, if any.",
 				Type:        schema.TypeString,
 				Required:    true,
 			},
+			// Optional inputs
+			"iteration_id": {
+				Description:  "HCP ID of this image. Either this or `channel' must be specified.",
+				Type:         schema.TypeString,
+				Optional:     true,
+				ExactlyOneOf: []string{"channel"},
+			},
+			"channel": {
+				Description:  "Channel that promotes the latest iteration of the image. Either this or `iteration_id` must be specified.",
+				Type:         schema.TypeString,
+				Optional:     true,
+				ExactlyOneOf: []string{"iteration_id"},
+			},
 			// computed outputs
 			"organization_id": {
 				Description: "The ID of the organization this HCP Packer registry is located in.",
@@ -95,9 +105,10 @@ func dataSourcePackerImage() *schema.Resource {
 
 func dataSourcePackerImageRead(ctx context.Context, d *schema.ResourceData, meta interface{}) diag.Diagnostics {
 	bucketName := d.Get("bucket_name").(string)
-	iterationID := d.Get("iteration_id").(string)
 	cloudProvider := d.Get("cloud_provider").(string)
 	region := d.Get("region").(string)
+	channelName := d.Get("channel")
+	iterationID := d.Get("iteration_id")
 	client := meta.(*clients.Client)
 
 	loc := &sharedmodels.HashicorpCloudLocationLocation{
@@ -111,9 +122,49 @@ func dataSourcePackerImageRead(ctx context.Context, d *schema.ResourceData, meta
 
 	log.Printf("[INFO] Reading HCP Packer registry (%s) [project_id=%s, organization_id=%s, iteration_id=%s]", bucketName, loc.ProjectID, loc.OrganizationID, iterationID)
 
-	iteration, err := clients.GetIterationFromId(ctx, client, loc, bucketName, iterationID)
-	if err != nil {
-		return diag.FromErr(err)
+	var iteration *packermodels.HashicorpCloudPackerIteration
+	var err error
+
+	if iterID, ok := iterationID.(string); ok && iterID != "" {
+		iteration, err = clients.GetIterationFromId(
+			ctx,
+			client,
+			loc,
+			bucketName,
+			iterID)
+		if err != nil {
+			return diag.FromErr(err)
+		}
+	}
+
+	var channel *packermodels.HashicorpCloudPackerChannel
+
+	if chanSlug, ok := channelName.(string); ok && chanSlug != "" {
+		channel, err = clients.GetPackerChannelBySlug(
+			ctx,
+			client,
+			loc,
+			bucketName,
+			chanSlug)
+		if err != nil {
+			return diag.FromErr(err)
+		}
+	}
+
+	var diags diag.Diagnostics
+
+	if channel != nil && iteration != nil {
+		return diag.FromErr(fmt.Errorf(
+			"iteration mismatch: channel %s's iteration (%s) is different from the explicitely specified iteration: %s",
+			channel.Slug,
+			channel.Iteration.ID,
+			iteration.ID))
+	}
+
+	// Assuming we passed the above check, the rest of the channel is not
+	// used after that,
+	if channel != nil {
+		iteration = channel.Iteration
 	}
 
 	found := false
@@ -159,5 +210,5 @@ func dataSourcePackerImageRead(ctx context.Context, d *schema.ResourceData, meta
 		return diag.Errorf("Unable to load image with region %s and cloud %s for iteration %s.", region, cloudProvider, iterationID)
 	}
 
-	return nil
+	return diags
 }

internal/provider/data_source_packer_image_test.go

@@ -3,6 +3,7 @@ package provider
 import (
 	"fmt"
 	"math/rand"
+	"regexp"
 	"testing"
 	"time"
 
@@ -14,6 +15,7 @@ import (
 const (
 	acctestImageBucket       = "alpine-acctest-imagetest"
 	acctestUbuntuImageBucket = "ubuntu-acctest-imagetest"
+	acctestArchImageBucket   = "arch-acctest-imagetest"
 	acctestImageChannel      = "production-image-test"
 )
 
@@ -50,6 +52,25 @@ var (
 		region         = "us-east-1"
 	}
 `, acctestUbuntuImageBucket, acctestImageChannel, acctestUbuntuImageBucket)
+
+	testAccPackerImageBothChanAndIter = fmt.Sprintf(`
+	data "hcp_packer_image" "arch-btw" {
+		bucket_name = %q
+		cloud_provider = "aws"
+		iteration_id = "234567"
+		channel = "chanSlug"
+		region = "us-east-1"
+	}
+`, acctestArchImageBucket)
+
+	testAccPackerImageArchProduction = fmt.Sprintf(`
+	data "hcp_packer_image" "arch-btw" {
+		bucket_name = %q
+		cloud_provider = "aws"
+		channel = %q
+		region = "us-east-1"
+	}
+`, acctestArchImageBucket, acctestImageChannel)
 )
 
 func TestAcc_dataSourcePackerImage(t *testing.T) {
@@ -134,3 +155,62 @@ func TestAcc_dataSourcePackerImage_revokedIteration(t *testing.T) {
 		},
 	})
 }
+
+func TestAcc_dataSourcePackerImage_channelAndIterationIDReject(t *testing.T) {
+	resource.Test(t, resource.TestCase{
+		ProviderFactories: providerFactories,
+		Steps: []resource.TestStep{
+			// basically just testing that we don't pass validation here
+			{
+				PlanOnly:    true,
+				Config:      testConfig(testAccPackerImageBothChanAndIter),
+				ExpectError: regexp.MustCompile("Error: Invalid combination of arguments"),
+			},
+		},
+	})
+}
+
+func TestAcc_dataSourcePackerImage_channelAccept(t *testing.T) {
+	fingerprint := "acceptChannel"
+	resourceName := "data.hcp_packer_image.arch-btw"
+	var buildID string
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:          func() { testAccPreCheck(t, map[string]bool{"aws": false, "azure": false}) },
+		ProviderFactories: providerFactories,
+		Steps: []resource.TestStep{
+			{
+				PlanOnly: true,
+				PreConfig: func() {
+					// CheckDestroy doesn't get called when the test fails and doesn't
+					// produce any tf state. In this case we destroy any existing resource
+					// before creating them.
+					deleteChannel(t, acctestArchImageBucket, acctestImageChannel, false)
+					deleteIteration(t, acctestArchImageBucket, fingerprint, false)
+					deleteBucket(t, acctestArchImageBucket, false)
+
+					upsertRegistry(t)
+					upsertBucket(t, acctestArchImageBucket)
+					upsertIteration(t, acctestArchImageBucket, fingerprint)
+					itID, err := getIterationIDFromFingerPrint(t, acctestArchImageBucket, fingerprint)
+					if err != nil {
+						t.Fatal(err.Error())
+					}
+					upsertBuild(t, acctestArchImageBucket, fingerprint, itID)
+					createChannel(t, acctestArchImageBucket, acctestImageChannel, itID)
+
+					buildID, err = getBuildIDFromIteration(t, acctestArchImageBucket, itID, "aws")
+					if err != nil {
+						t.Fatal(err.Error())
+					}
+				},
+				Config: testConfig(testAccPackerImageArchProduction),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttrSet(resourceName, "organization_id"),
+					resource.TestCheckResourceAttrSet(resourceName, "project_id"),
+					resource.TestCheckResourceAttr(resourceName, "iteration-id", buildID),
+				),
+			},
+		},
+	})
+}