config: add platform-agnostic 'target' property

Today the receiver config requires platform-specific fields to specify
the listen path: 'pipe' on Windows (a named pipe path) and 'socket'
on Unix (a Unix domain socket path). This means configs that use
environment variable substitution via the ${env:VAR} syntax cannot
use a single property that works across both platforms, since the
field name itself is platform-specific.

Add a new 'target' field that acts as a platform-agnostic alternative.
During Validate(), when 'target' is set, its value is copied into the
appropriate platform-specific field: NamedPipePath on Windows and
UnixSocketPath on Unix. The existing normalization logic then handles
the value as usual, including named pipe prefix expansion on Windows
and af_unix: prefix stripping on Unix.

It is an error to specify both 'target' and the platform-specific
field ('pipe' or 'socket'), since the intent would be ambiguous.

Add tests covering the target-to-socket mapping on Unix (with and
without af_unix: prefix), the target-to-pipe mapping on Windows,
and the conflict error for both platforms.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com>

Author: mjcheetham

config.go

@@ -41,6 +41,18 @@ type Config struct {
 	// This config file field is ignored on Windows platforms.
 	UnixSocketPath string `mapstructure:"socket"`
 
+	// A combination of either a NamedPipePath or a UnixSocketPath.
+	// On Unix this can only be considered as a Unix domain socket,
+	// and on Windows we can only consider it as a named pipe.
+	// This allows the user to specify a property that works for
+	// either platform, and we will normalize it to the correct one
+	// at runtime. If both are specified we consider this an error.
+	// The idea behind this is to allow users to specify the value
+	// of the Target property as an environment variable via the
+	// ${env:VAR} syntax, and then use that environment variable to
+	// set the correct path for their platform.
+	Target string `mapstructure:"target"`
+
 	// Allow command and control verbs to be embedded in the Trace2
 	// data stream.
 	AllowCommandControlVerbs bool `mapstructure:"enable_commands"`
@@ -79,6 +91,23 @@ func (cfg *Config) Validate() error {
 	var path string
 	var err error
 
+	// If `target` is set, normalize it into the platform-specific
+	// field.  It is an error to set both `target` and the
+	// platform-specific field.
+	if len(cfg.Target) > 0 {
+		if runtime.GOOS == "windows" {
+			if len(cfg.NamedPipePath) > 0 {
+				return fmt.Errorf("receivers.trace2receiver: cannot specify both 'target' and 'pipe'")
+			}
+			cfg.NamedPipePath = cfg.Target
+		} else {
+			if len(cfg.UnixSocketPath) > 0 {
+				return fmt.Errorf("receivers.trace2receiver: cannot specify both 'target' and 'socket'")
+			}
+			cfg.UnixSocketPath = cfg.Target
+		}
+	}
+
 	if runtime.GOOS == "windows" {
 		if len(cfg.NamedPipePath) == 0 {
 			return fmt.Errorf("receivers.trace2receiver.pipe not defined")

config_test.go

@@ -356,6 +356,83 @@ func Test_Config_Validate_WithCommandControlEnabled(t *testing.T) {
 	assert.NoError(t, err)
 }
 
+// Test Validate with Target on Unix sets UnixSocketPath
+func Test_Config_Validate_TargetUnix(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Skipping Unix-specific test")
+	}
+
+	cfg := &Config{
+		Target: "/tmp/test.socket",
+	}
+
+	err := cfg.Validate()
+	assert.NoError(t, err)
+	assert.Equal(t, "/tmp/test.socket", cfg.UnixSocketPath)
+}
+
+// Test Validate with Target with af_unix prefix on Unix
+func Test_Config_Validate_TargetAfUnixPrefixUnix(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Skipping Unix-specific test")
+	}
+
+	cfg := &Config{
+		Target: "af_unix:/tmp/test.socket",
+	}
+
+	err := cfg.Validate()
+	assert.NoError(t, err)
+	assert.Equal(t, "/tmp/test.socket", cfg.UnixSocketPath)
+}
+
+// Test Validate with Target on Windows sets NamedPipePath
+func Test_Config_Validate_TargetWindows(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("Skipping Windows-specific test")
+	}
+
+	cfg := &Config{
+		Target: "test-pipe",
+	}
+
+	err := cfg.Validate()
+	assert.NoError(t, err)
+	assert.Equal(t, `\\.\pipe\test-pipe`, cfg.NamedPipePath)
+}
+
+// Test Validate rejects Target and socket both set on Unix
+func Test_Config_Validate_TargetAndSocketConflictUnix(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("Skipping Unix-specific test")
+	}
+
+	cfg := &Config{
+		Target:         "/tmp/target.socket",
+		UnixSocketPath: "/tmp/test.socket",
+	}
+
+	err := cfg.Validate()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "cannot specify both 'target' and 'socket'")
+}
+
+// Test Validate rejects Target and pipe both set on Windows
+func Test_Config_Validate_TargetAndPipeConflictWindows(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("Skipping Windows-specific test")
+	}
+
+	cfg := &Config{
+		Target:        "target-pipe",
+		NamedPipePath: "test-pipe",
+	}
+
+	err := cfg.Validate()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "cannot specify both 'target' and 'pipe'")
+}
+
 // Helper function to create a minimal valid config for the current platform
 func createMinimalValidConfig() *Config {
 	if runtime.GOOS == "windows" {