registry: prevent panic in list v2 (#1391)

Fixes #1390

Prevents a panic in the registry's list V2 command caused by attempting
to access fields on a struct that can be `nil`.

commands/displayers/registry.go

@@ -16,6 +16,7 @@ package displayers
 import (
  "fmt"
  "io"
+ "time"
 
  "github.com/digitalocean/doctl/do"
 )
@@ -143,17 +144,25 @@ func (r *RepositoryV2) KV() []map[string]interface{} {
  out := make([]map[string]interface{}, 0, len(r.Repositories))
 
  for _, reg := range r.Repositories {
+ var latestManifest string
  latestTag := "<none>" // default when latest manifest has no tags
- if len(reg.LatestManifest.Tags) > 0 {
- latestTag = reg.LatestManifest.Tags[0]
+ var latestUpdate *time.Time
+
+ if reg.LatestManifest != nil {
+ latestManifest = reg.LatestManifest.Digest
+ if len(reg.LatestManifest.Tags) > 0 {
+ latestTag = reg.LatestManifest.Tags[0]
+ }
+ latestUpdate = &reg.LatestManifest.UpdatedAt
  }
+
  m := map[string]interface{}{
  "Name": reg.Name,
- "LatestManifest": reg.LatestManifest.Digest,
+ "LatestManifest": latestManifest,
  "LatestTag": latestTag,
  "TagCount": reg.TagCount,
  "ManifestCount": reg.ManifestCount,
- "UpdatedAt": reg.LatestManifest.UpdatedAt,
+ "UpdatedAt": latestUpdate,
  }
 
  out = append(out, m)

integration/registry_repo_list_v2_test.go

@@ -82,6 +82,7 @@ var (
  repositoryListV2Output = `
 Name Latest Manifest Latest Tag Tag Count Manifest Count Updated At
 repo-1 sha256:cb8a924afdf0229ef7515d9e5b3024e23b3eb03ddbba287f4a19c6ac90b8d221 v1 57 82 2021-04-09 23:54:25 +0000 UTC
+repo-2 <none> 57 82 <nil>
 `
 
  repositoryListV2Response = `{
@@ -117,10 +118,16 @@ repo-1 sha256:cb8a924afdf0229ef7515d9e5b3024e23b3eb03ddbba287f4a19c6ac90b8d22
  }
  ]
  }
+ },
+ {
+ "registry_name": "example-no-latest-manifest",
+ "name": "repo-2",
+ "tag_count": 57,
+ "manifest_count": 82
  }
  ],
  "meta": {
- "total": 1
+ "total": 2
  }
 }`
 )