Add BAZELISK_DISABLE_COMPLETION to allow bypass completion interception

README.md

@@ -211,6 +211,17 @@ The bazel completion scripts are taken from installer binaries. If you use a
 custom base URL, make sure the installer URLs are available alongside with
 bazel binaries.
 
+#### Disabling Bazelisk's completion handler
+
+If the underlying Bazel binary provides its own `completion` command with
+broader shell support (e.g. zsh), you can disable Bazelisk's built-in
+completion handling so that the command is passed through to the underlying
+binary. Set `BAZELISK_DISABLE_COMPLETION` in your `.bazeliskrc`:
+
+```shell
+BAZELISK_DISABLE_COMPLETION=1
+```
+
 ### Useful environment variables for --migrate and --bisect
 
 You can set `BAZELISK_INCOMPATIBLE_FLAGS` to set a list of incompatible flags (separated by `,`) to be tested, otherwise Bazelisk tests all flags starting with `--incompatible_`.
@@ -259,6 +270,7 @@ The following variables can be set:
 - `BAZELISK_FORMAT_URL`
 - `BAZELISK_NOJDK`
 - `BAZELISK_CLEAN`
+- `BAZELISK_DISABLE_COMPLETION`
 - `BAZELISK_GITHUB_TOKEN`
 - `BAZELISK_HOME_DARWIN`
 - `BAZELISK_HOME_LINUX`

core/core.go

@@ -176,7 +176,7 @@ func RunBazeliskWithArgsFuncAndConfigAndOutAndErr(argsFunc ArgsFunc, repos *Repo
 	}
 
 	// handle completion command
-	if isCompletionCommand(args) {
+	if isCompletionCommand(args) && config.Get("BAZELISK_DISABLE_COMPLETION") == "" {
 		err := handleCompletionCommand(args, bazelInstallation, config)
 		if err != nil {
 			if errors.Is(err, httputil.NotFound) {

core/core_test.go

@@ -353,6 +353,59 @@ func TestIsCompletionCommand(t *testing.T) {
 	}
 }
 
+func TestDisableCompletionConfig(t *testing.T) {
+	testCases := []struct {
+		name           string
+		args           []string
+		configValue    string
+		shouldIntercept bool
+	}{
+		{
+			name:           "completion intercepted by default",
+			args:           []string{"completion", "bash"},
+			configValue:    "",
+			shouldIntercept: true,
+		},
+		{
+			name:           "completion disabled with config",
+			args:           []string{"completion", "bash"},
+			configValue:    "1",
+			shouldIntercept: false,
+		},
+		{
+			name:           "completion disabled with any non-empty value",
+			args:           []string{"completion", "zsh"},
+			configValue:    "true",
+			shouldIntercept: false,
+		},
+		{
+			name:           "non-completion command unaffected",
+			args:           []string{"build", "//..."},
+			configValue:    "",
+			shouldIntercept: false,
+		},
+		{
+			name:           "non-completion command unaffected with config",
+			args:           []string{"build", "//..."},
+			configValue:    "1",
+			shouldIntercept: false,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			cfg := config.Static(map[string]string{
+				"BAZELISK_DISABLE_COMPLETION": tc.configValue,
+			})
+			result := isCompletionCommand(tc.args) && cfg.Get("BAZELISK_DISABLE_COMPLETION") == ""
+			if result != tc.shouldIntercept {
+				t.Errorf("completion interception for args=%v, BAZELISK_DISABLE_COMPLETION=%q: got %v, want %v",
+					tc.args, tc.configValue, result, tc.shouldIntercept)
+			}
+		})
+	}
+}
+
 func TestConstructInstallerURL(t *testing.T) {
 	testCases := []struct {
 		name        string