add helper for inferring index name from input

To be used in multi-index work.

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

internal/pathutil/pathutil.go

@@ -19,6 +19,8 @@ import (
 	"strings"
 
 	"github.com/pkg/errors"
+
+	"sigs.k8s.io/krew/pkg/constants"
 )
 
 // IsSubPath checks if the extending path is an extension of the basePath, it will return the extending path
@@ -42,3 +44,13 @@ func ReplaceBase(path, old, replacement string) (string, error) {
 	}
 	return filepath.Join(replacement, extendingPath), nil
 }
+
+// CanonicalPluginName resolves a plugin's index and name from input string.
+// If an index is not specified, the default index name is assumed.
+func CanonicalPluginName(in string) (string, string) {
+	p := strings.SplitN(in, "/", 2)
+	if strings.Count(in, "/") == 0 {
+		return constants.DefaultIndexName, in
+	}
+	return p[0], p[1]
+}

internal/pathutil/pathutil_test.go

@@ -184,3 +184,27 @@ func TestReplaceBase(t *testing.T) {
 		})
 	}
 }
+
+func TestCanonicalPluginName(t *testing.T) {
+	tests := []struct {
+		in        string
+		wantIndex string
+		wantName  string
+	}{
+		{"foo", "default", "foo"},
+		{"", "default", ""}, // despite unsupported
+		{"a/b", "a", "b"},
+		{"a/b/c", "a", "b/c"}, // despite unsupported
+	}
+	for _, tt := range tests {
+		t.Run(tt.in, func(t *testing.T) {
+			gotIndex, gotName := CanonicalPluginName(tt.in)
+			if gotIndex != tt.wantIndex {
+				t.Errorf("CanonicalPluginName(%q) gotIndex = %q, want = %q", tt.in, gotIndex, tt.wantIndex)
+			}
+			if gotName != tt.wantName {
+				t.Errorf("CanonicalPluginName(%q) gotName = %q, want = %q", tt.in, gotName, tt.wantName)
+			}
+		})
+	}
+}

pkg/constants/constants.go

@@ -21,5 +21,6 @@ const (
 	KrewPluginName    = "krew" // plugin name of krew itself
 
 	// IndexURI points to the upstream index.
-	IndexURI = "https://github.com/kubernetes-sigs/krew-index.git"
+	IndexURI         = "https://github.com/kubernetes-sigs/krew-index.git"
+	DefaultIndexName = "default"
 )