plugin/discovery: create target plugin directory if it does not exist (#20575)

If the user supplies a plugin cache dir, the provider installer was not
checking if target directory exists before linking the cached pluging.

plugin/discovery/get.go

@@ -270,6 +270,14 @@ func (i *ProviderInstaller) install(provider string, version Version, url string
 		// normal resolution machinery can find it.
 		filename := filepath.Base(cached)
 		targetPath := filepath.Join(i.Dir, filename)
+		// check if the target dir exists, and create it if not
+		var err error
+		if _, StatErr := os.Stat(i.Dir); os.IsNotExist(StatErr) {
+			err = os.Mkdir(i.Dir, 0700)
+		}
+		if err != nil {
+			return err
+		}
 
 		log.Printf("[DEBUG] installing %s %s to %s from local cache %s", provider, version, targetPath, cached)
 

plugin/discovery/get_test.go

@@ -474,6 +474,63 @@ func TestProviderInstallerGet(t *testing.T) {
 
 }
 
+// test that the provider installer can install plugins from a plugin cache dir
+// into a target directory that does not exist.
+//  https://github.com/hashicorp/terraform/issues/20532
+func TestProviderInstallerGet_cache(t *testing.T) {
+	server := testReleaseServer()
+	server.Start()
+	defer server.Close()
+
+	tmpDir, err := ioutil.TempDir("", "tf-plugin")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cache := NewLocalPluginCache(filepath.Join(tmpDir, "cache"))
+	targetDir := filepath.Join(tmpDir, "non-existant-dir")
+
+	defer os.RemoveAll(tmpDir)
+
+	i := &ProviderInstaller{
+		Dir:                   targetDir,
+		Cache:                 cache,
+		PluginProtocolVersion: 4,
+		SkipVerify:            true,
+		Ui:                    cli.NewMockUi(),
+		registry:              registry.NewClient(Disco(server), nil),
+		OS:                    "mockos",
+		Arch:                  "mockarch",
+	}
+
+	gotMeta, err := i.Get("test", AllVersions)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// we should have version 1.2.4
+	dest := filepath.Join(targetDir, "terraform-provider-test_v1.2.4")
+
+	wantMeta := PluginMeta{
+		Name:    "test",
+		Version: VersionStr("1.2.4"),
+		Path:    dest,
+	}
+	if !reflect.DeepEqual(gotMeta, wantMeta) {
+		t.Errorf("wrong result meta\ngot:  %#v\nwant: %#v", gotMeta, wantMeta)
+	}
+
+	f, err := ioutil.ReadFile(dest)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// provider should have been unzipped
+	if string(f) != testProviderFile {
+		t.Fatalf("test provider contains: %q", f)
+	}
+}
+
 func TestProviderInstallerPurgeUnused(t *testing.T) {
 	server := testReleaseServer()
 	defer server.Close()