add tests

Signed-off-by: Suleiman Dibirov <idsulik@gmail.com>

internal/plugin/installer/http_installer_test.go

@@ -127,6 +127,58 @@ func TestHTTPInstaller(t *testing.T) {
 
 }
 
+func TestHTTPInstallerPluginAlreadyExists(t *testing.T) {
+	ensure.HelmHome(t)
+
+	srv := mockArchiveServer()
+	defer srv.Close()
+	source := srv.URL + "/plugins/fake-plugin-0.0.1.tar.gz"
+
+	if err := os.MkdirAll(helmpath.DataPath("plugins"), 0755); err != nil {
+		t.Fatalf("Could not create %s: %s", helmpath.DataPath("plugins"), err)
+	}
+
+	i, err := NewForSource(source, "0.0.1")
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	// ensure a HTTPInstaller was returned
+	httpInstaller, ok := i.(*HTTPInstaller)
+	if !ok {
+		t.Fatal("expected a HTTPInstaller")
+	}
+
+	// inject fake http client responding with minimal plugin tarball
+	mockTgz, err := base64.StdEncoding.DecodeString(fakePluginB64)
+	if err != nil {
+		t.Fatalf("Could not decode fake tgz plugin: %s", err)
+	}
+
+	httpInstaller.getter = &TestHTTPGetter{
+		MockResponse: bytes.NewBuffer(mockTgz),
+	}
+
+	// First install should succeed
+	if err := Install(i); err != nil {
+		t.Fatal(err)
+	}
+
+	// Reset the getter mock for second install attempt
+	httpInstaller.getter = &TestHTTPGetter{
+		MockResponse: bytes.NewBuffer(mockTgz),
+	}
+
+	// Second install should fail with specific error message
+	err = httpInstaller.Install()
+	if err == nil {
+		t.Fatal("expected error for plugin already exists")
+	}
+	if !strings.Contains(err.Error(), "plugin \"fake-plugin\" already exists at") {
+		t.Fatalf("expected 'plugin already exists' error message, got: %v", err)
+	}
+}
+
 func TestHTTPInstallerNonExistentVersion(t *testing.T) {
 	ensure.HelmHome(t)
 	srv := mockArchiveServer()

internal/plugin/installer/local_installer_test.go

@@ -21,6 +21,7 @@ import (
 	"compress/gzip"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"helm.sh/helm/v4/internal/test/ensure"
@@ -146,3 +147,116 @@ func TestLocalInstallerTarball(t *testing.T) {
 		t.Fatalf("plugin not found at %s: %v", i.Path(), err)
 	}
 }
+
+func TestLocalInstallerDirectoryAlreadyExists(t *testing.T) {
+	ensure.HelmHome(t)
+
+	source := "../testdata/plugdir/good/echo-v1"
+	i, err := NewForSource(source, "")
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	// First install should succeed
+	if err := Install(i); err != nil {
+		t.Fatal(err)
+	}
+
+	// Create another installer for the same plugin directory
+	i2, err := NewForSource(source, "")
+	if err != nil {
+		t.Fatalf("unexpected error creating second installer: %s", err)
+	}
+
+	localInstaller, ok := i2.(*LocalInstaller)
+	if !ok {
+		t.Fatal("expected LocalInstaller")
+	}
+
+	// Second install should fail with plugin already exists error
+	err = localInstaller.installFromDirectory()
+	if err == nil {
+		t.Fatal("expected error for plugin already exists")
+	}
+	if !strings.Contains(err.Error(), "plugin \"echo-v1\" already exists at") {
+		t.Fatalf("expected 'plugin already exists' error message, got: %v", err)
+	}
+}
+
+func TestLocalInstallerTarballAlreadyExists(t *testing.T) {
+	ensure.HelmHome(t)
+
+	// Create a test tarball
+	tempDir := t.TempDir()
+	tarballPath := filepath.Join(tempDir, "duplicate-plugin-1.0.0.tar.gz")
+
+	// Create tarball content
+	var buf bytes.Buffer
+	gw := gzip.NewWriter(&buf)
+	tw := tar.NewWriter(gw)
+
+	files := []struct {
+		Name string
+		Body string
+		Mode int64
+	}{
+		{"duplicate-plugin/plugin.yaml", "name: duplicate-plugin\napiVersion: v1\ntype: cli/v1\nruntime: subprocess\nversion: 1.0.0\nconfig:\n  shortHelp: test\n  longHelp: test\nruntimeConfig:\n  platformCommand:\n  - command: echo", 0644},
+		{"duplicate-plugin/bin/duplicate-plugin", "#!/bin/bash\necho test", 0755},
+	}
+
+	for _, file := range files {
+		hdr := &tar.Header{
+			Name: file.Name,
+			Mode: file.Mode,
+			Size: int64(len(file.Body)),
+		}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := tw.Write([]byte(file.Body)); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	if err := tw.Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := gw.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Write tarball to file
+	if err := os.WriteFile(tarballPath, buf.Bytes(), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	// First install
+	i, err := NewForSource(tarballPath, "")
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	if err := Install(i); err != nil {
+		t.Fatal(err)
+	}
+
+	// Create second installer for same tarball
+	i2, err := NewForSource(tarballPath, "")
+	if err != nil {
+		t.Fatalf("unexpected error creating second installer: %s", err)
+	}
+
+	localInstaller, ok := i2.(*LocalInstaller)
+	if !ok {
+		t.Fatal("expected LocalInstaller")
+	}
+
+	// Second install should fail
+	err = localInstaller.installFromArchive()
+	if err == nil {
+		t.Fatal("expected error for plugin already exists")
+	}
+	if !strings.Contains(err.Error(), "plugin \"duplicate-plugin\" already exists at") {
+		t.Fatalf("expected 'plugin already exists' error message, got: %v", err)
+	}
+}

internal/plugin/installer/vcs_installer_test.go

@@ -103,6 +103,63 @@ func TestVCSInstaller(t *testing.T) {
 	}
 }
 
+func TestVCSInstallerPluginAlreadyExists(t *testing.T) {
+	ensure.HelmHome(t)
+
+	if err := os.MkdirAll(helmpath.DataPath("plugins"), 0755); err != nil {
+		t.Fatalf("Could not create %s: %s", helmpath.DataPath("plugins"), err)
+	}
+
+	source := "https://github.com/adamreese/helm-env"
+	testRepoPath, _ := filepath.Abs("../testdata/plugdir/good/echo-v1")
+	repo := &testRepo{
+		local: testRepoPath,
+		tags:  []string{"0.1.0", "0.1.1"},
+	}
+
+	i, err := NewForSource(source, "~0.1.0")
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	// ensure a VCSInstaller was returned
+	vcsInstaller, ok := i.(*VCSInstaller)
+	if !ok {
+		t.Fatal("expected a VCSInstaller")
+	}
+
+	// set the testRepo in the VCSInstaller
+	vcsInstaller.Repo = repo
+
+	// First install should succeed
+	if err := Install(i); err != nil {
+		t.Fatal(err)
+	}
+
+	// Create a second VCS installer for the same plugin
+	i2, err := NewForSource(source, "~0.1.0")
+	if err != nil {
+		t.Fatalf("unexpected error: %s", err)
+	}
+
+	vcsInstaller2, ok := i2.(*VCSInstaller)
+	if !ok {
+		t.Fatal("expected a VCSInstaller")
+	}
+
+	// set the testRepo in the VCSInstaller
+	vcsInstaller2.Repo = repo
+
+	// Second install should fail with plugin already exists error
+	err = vcsInstaller2.Install()
+	if err == nil {
+		t.Fatal("expected error for plugin already exists")
+	}
+	if !strings.Contains(err.Error(), "plugin \"echo-v1\" already exists at") {
+		t.Fatalf("expected 'plugin already exists' error message, got: %v", err)
+	}
+}
+
 func TestVCSInstallerNonExistentVersion(t *testing.T) {
 	ensure.HelmHome(t)