Add feature flags from environment variable (#722)

* Add featuretoggles package

* Change featuretoggles to experimental package

* Update folder.golden.txt

---------

Co-authored-by: Giuseppe Guerra <[email protected]>

experimental/featuretoggles/featuretoggles.go

@@ -0,0 +1,47 @@
+package featuretoggles
+
+import (
+	"os"
+	"strings"
+)
+
+// envFeatureTogglesEnable is the environment variable set by Grafana containing the list of enabled feature toggles.
+const envFeatureTogglesEnable = "GF_INSTANCE_FEATURE_TOGGLES_ENABLE"
+
+// FeatureToggles can check if feature toggles are enabled on the Grafana instance.
+type FeatureToggles interface {
+	// IsEnabled returns true if the provided feature flag is set.
+	IsEnabled(flag string) bool
+}
+
+// featureToggles implements a FeatureToggles that returns true if a flag is present in the flags map.
+type featureToggles struct {
+	// flags is a set-like map of feature flags that are enabled.
+	flags map[string]struct{}
+}
+
+// IsEnabled returns true if flag is contained in f.flags.
+func (f featureToggles) IsEnabled(flag string) bool {
+	_, ok := f.flags[flag]
+	return ok
+}
+
+// newFeatureTogglesFromEnv returns a new featureToggles instance with its flags set from environment variables.
+func newFeatureTogglesFromEnv() featureToggles {
+	return featureToggles{flags: flagsMapFromEnv()}
+}
+
+// flagsMapFromEnv returns a new set-like map[string]struct{}, where the keys are the space-separated names in
+// the `envFeatureTogglesEnable` env var.
+func flagsMapFromEnv() map[string]struct{} {
+	flags := strings.Split(os.Getenv(envFeatureTogglesEnable), ",")
+	r := make(map[string]struct{}, len(flags))
+	for _, flag := range flags {
+		r[flag] = struct{}{}
+	}
+	return r
+}
+
+// DefaultFeatureToggles is the default feature toggles implementation.
+// It contains the same feature toggles as the Grafana instance where the plugin is running.
+var DefaultFeatureToggles FeatureToggles = newFeatureTogglesFromEnv()

experimental/featuretoggles/featuretoggles_test.go

@@ -0,0 +1,30 @@
+package featuretoggles
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestEnvFeatureToggles(t *testing.T) {
+	t.Run("should work when flag is provided", func(t *testing.T) {
+		t.Setenv(envFeatureTogglesEnable, "")
+		flags := newFeatureTogglesFromEnv()
+		require.False(t, flags.IsEnabled("abc"))
+	})
+
+	t.Run("should work when single flag is provided", func(t *testing.T) {
+		t.Setenv(envFeatureTogglesEnable, "abc")
+		flags := newFeatureTogglesFromEnv()
+		require.True(t, flags.IsEnabled("abc"))
+		require.False(t, flags.IsEnabled("def"))
+	})
+
+	t.Run("should work when multiple flags are provided", func(t *testing.T) {
+		t.Setenv(envFeatureTogglesEnable, "abc,def")
+		flags := newFeatureTogglesFromEnv()
+		require.True(t, flags.IsEnabled("abc"))
+		require.True(t, flags.IsEnabled("def"))
+		require.False(t, flags.IsEnabled("ghi"))
+	})
+}

experimental/testdata/folder.golden.txt

@@ -9,24 +9,24 @@ Frame[0] {
     "pathSeparator": "/"
 }
 Name: 
-Dimensions: 2 Fields by 17 Rows
-+----------------------+------------------+
-| Name: name           | Name: media-type |
-| Labels:              | Labels:          |
-| Type: []string       | Type: []string   |
-+----------------------+------------------+
-| README.md            |                  |
-| actions              | directory        |
-| authclient           | directory        |
-| datasourcetest       | directory        |
-| e2e                  | directory        |
-| fileinfo.go          |                  |
-| fileinfo_test.go     |                  |
-| frame_sorter.go      |                  |
-| frame_sorter_test.go |                  |
-| ...                  | ...              |
-+----------------------+------------------+
+Dimensions: 2 Fields by 18 Rows
++------------------+------------------+
+| Name: name       | Name: media-type |
+| Labels:          | Labels:          |
+| Type: []string   | Type: []string   |
++------------------+------------------+
+| README.md        |                  |
+| actions          | directory        |
+| authclient       | directory        |
+| datasourcetest   | directory        |
+| e2e              | directory        |
+| featuretoggles   | directory        |
+| fileinfo.go      |                  |
+| fileinfo_test.go |                  |
+| frame_sorter.go  |                  |
+| ...              | ...              |
++------------------+------------------+
 
 
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