Cleanup pluginmanager of unused feature flag code (#484)

This commit removes all the unused code around feature flags from the
`manager.go` file.  Those changes are:
1. Remove `ValidatePlugin()` which was never used.  There is a
   separate copy of this function in the tanzu-plugin-runtime repository.
2. Remove `discoverPlugins()` and directly use `discoverSpecificPlugins()`
3. Remove `discoverServerPluginsBasedOnCurrentServer` which is no longer
   used.
4. Include the logic of `discoverServerPluginsBasedOnAllCurrentContexts()`
   directly into `DiscoverServerPlugins()` which had become a one-liner.
5. Remove the following functions that were no longer used:
      - `AvailablePlugins()`
      - `AvailablePluginsFromLocalSource()`
      - `availablePlugins()`
      - `combineDuplicatePlugins()`
      - `getInstalledButNotDiscoveredStandalonePlugins()`
      - `DiscoveredFromPlugininfo()`
      - `availablePluginsFromStandaloneAndServerPlugins()`
      - `pluginIndexForName()`
      - `legacyPluginInstall()`
      - `GetRecommendedVersionOfPlugin()`

Completely remove the feature flag constant:
  FeatureDisableCentralRepositoryForTesting

* Update the unit tests for the plugin manager.

This commit improves our ability to test the pluginmanager.
It does this using two techniques:

1. Creating a test plugin inventory DB in the cache and requesting the
   inventory code to always use the cache (without checking the digest).
   To force the use of the cache the commit introduces a test variable
   `TEST_TANZU_CLI_USE_DB_CACHE_ONLY`.
   This approach allows to discover plugins and groups without needing
   a real OCI registry.

2. Creating "fake" plugin binaries in the plugin binary cache.  This
   allows installation of plugins to find the binaries in the cache and
   therefore never have to go to an OCI registry to download them.

With these two techniques, the unit tests can discovery and install
plugins, and can also do so using groups.  The plugin sync can also be
tested with this.

Note: the unit tests would still benefit from some tests moving to this
approach of testing, but this will need to come in a future effort.

Signed-off-by: Marc Khouzam <[email protected]>

go.mod

@@ -43,7 +43,6 @@ require (
 	github.com/vmware-tanzu/tanzu-framework/capabilities/client v0.0.0-20230523145612-1c6fbba34686
 	github.com/vmware-tanzu/tanzu-plugin-runtime v1.0.0
 	go.pinniped.dev v0.20.0
-	go.uber.org/multierr v1.11.0
 	golang.org/x/mod v0.10.0
 	golang.org/x/oauth2 v0.8.0
 	golang.org/x/sync v0.2.0
@@ -212,6 +211,7 @@ require (
 	go.opentelemetry.io/otel v1.15.0 // indirect
 	go.opentelemetry.io/otel/trace v1.15.0 // indirect
 	go.uber.org/atomic v1.10.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
 	go.uber.org/zap v1.24.0 // indirect
 	golang.org/x/crypto v0.9.0 // indirect
 	golang.org/x/exp v0.0.0-20230321023759-10a507213a29 // indirect

pkg/constants/featureflags.go

@@ -7,8 +7,6 @@ package constants
 const (
 	// FeatureContextCommand determines whether to surface the context command. This is disabled by default.
 	FeatureContextCommand = "features.global.context-target-v2"
-	// FeatureDisableCentralRepositoryForTesting determines if the CLI uses the Central Repository of plugins.
-	FeatureDisableCentralRepositoryForTesting = "features.global.no-central-repo-test-only"
 )
 
 // DefaultCliFeatureFlags is used to populate an initially empty config file with default values for feature flags.

pkg/discovery/oci.go

@@ -4,8 +4,10 @@
 package discovery
 
 import (
+	"os"
 	"path"
 	"path/filepath"
+	"strconv"
 
 	"github.com/vmware-tanzu/tanzu-cli/pkg/common"
 	"github.com/vmware-tanzu/tanzu-cli/pkg/plugininventory"
@@ -22,6 +24,10 @@ func NewOCIDiscovery(name, image string, options ...DiscoveryOptions) Discovery
 	discovery := newDBBackedOCIDiscovery(name, image)
 	discovery.pluginCriteria = opts.PluginDiscoveryCriteria
 	discovery.useLocalCacheOnly = opts.UseLocalCacheOnly
+	// NOTE: the use of TEST_TANZU_CLI_USE_DB_CACHE_ONLY is for testing only
+	if useCacheOnlyForTesting, _ := strconv.ParseBool(os.Getenv("TEST_TANZU_CLI_USE_DB_CACHE_ONLY")); useCacheOnlyForTesting {
+		discovery.useLocalCacheOnly = true
+	}
 	return discovery
 }
 
@@ -36,6 +42,10 @@ func NewOCIGroupDiscovery(name, image string, options ...DiscoveryOptions) Group
 	discovery := newDBBackedOCIDiscovery(name, image)
 	discovery.groupCriteria = opts.GroupDiscoveryCriteria
 	discovery.useLocalCacheOnly = opts.UseLocalCacheOnly
+	// NOTE: the use of TEST_TANZU_CLI_USE_DB_CACHE_ONLY is for testing only
+	if useCacheOnlyForTesting, _ := strconv.ParseBool(os.Getenv("TEST_TANZU_CLI_USE_DB_CACHE_ONLY")); useCacheOnlyForTesting {
+		discovery.useLocalCacheOnly = true
+	}
 
 	return discovery
 }