[configtls] Add omitempty tags to fields (#12311)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

This will dramatically reduce YAML output when marshaling config for
many receivers and exporters since it's commonly used.

<!-- Issue number if applicable -->
#### Link to tracking issue

Works toward #12191

.chloggen/configtls-omitempty.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: configtls
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add the `omitempty` mapstructure tag to struct fields
+
+# One or more tracking issues or pull requests related to the change
+issues: [12191]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: This results in unset fields not being rendered when marshaling.
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

config/configtls/configtls.go

@@ -33,48 +33,48 @@ type Config struct {
 	// Path to the CA cert. For a client this verifies the server certificate.
 	// For a server this verifies client certificates. If empty uses system root CA.
 	// (optional)
-	CAFile string `mapstructure:"ca_file"`
+	CAFile string `mapstructure:"ca_file,omitempty"`
 
 	// In memory PEM encoded cert. (optional)
-	CAPem configopaque.String `mapstructure:"ca_pem"`
+	CAPem configopaque.String `mapstructure:"ca_pem,omitempty"`
 
 	// If true, load system CA certificates pool in addition to the certificates
 	// configured in this struct.
-	IncludeSystemCACertsPool bool `mapstructure:"include_system_ca_certs_pool"`
+	IncludeSystemCACertsPool bool `mapstructure:"include_system_ca_certs_pool,omitempty"`
 
 	// Path to the TLS cert to use for TLS required connections. (optional)
-	CertFile string `mapstructure:"cert_file"`
+	CertFile string `mapstructure:"cert_file,omitempty"`
 
 	// In memory PEM encoded TLS cert to use for TLS required connections. (optional)
-	CertPem configopaque.String `mapstructure:"cert_pem"`
+	CertPem configopaque.String `mapstructure:"cert_pem,omitempty"`
 
 	// Path to the TLS key to use for TLS required connections. (optional)
-	KeyFile string `mapstructure:"key_file"`
+	KeyFile string `mapstructure:"key_file,omitempty"`
 
 	// In memory PEM encoded TLS key to use for TLS required connections. (optional)
-	KeyPem configopaque.String `mapstructure:"key_pem"`
+	KeyPem configopaque.String `mapstructure:"key_pem,omitempty"`
 
 	// MinVersion sets the minimum TLS version that is acceptable.
 	// If not set, TLS 1.2 will be used. (optional)
-	MinVersion string `mapstructure:"min_version"`
+	MinVersion string `mapstructure:"min_version,omitempty"`
 
 	// MaxVersion sets the maximum TLS version that is acceptable.
 	// If not set, refer to crypto/tls for defaults. (optional)
-	MaxVersion string `mapstructure:"max_version"`
+	MaxVersion string `mapstructure:"max_version,omitempty"`
 
 	// CipherSuites is a list of TLS cipher suites that the TLS transport can use.
 	// If left blank, a safe default list is used.
 	// See https://go.dev/src/crypto/tls/cipher_suites.go for a list of supported cipher suites.
-	CipherSuites []string `mapstructure:"cipher_suites"`
+	CipherSuites []string `mapstructure:"cipher_suites,omitempty"`
 
 	// ReloadInterval specifies the duration after which the certificate will be reloaded
 	// If not set, it will never be reloaded (optional)
-	ReloadInterval time.Duration `mapstructure:"reload_interval"`
+	ReloadInterval time.Duration `mapstructure:"reload_interval,omitempty"`
 
 	// contains the elliptic curves that will be used in
 	// an ECDHE handshake, in preference order
 	// Defaults to empty list and "crypto/tls" defaults are used, internally.
-	CurvePreferences []string `mapstructure:"curve_preferences"`
+	CurvePreferences []string `mapstructure:"curve_preferences,omitempty"`
 }
 
 // NewDefaultConfig creates a new TLSSetting with any default values set.
@@ -95,13 +95,13 @@ type ClientConfig struct {
 	// See https://godoc.org/google.golang.org/grpc#WithInsecure for gRPC.
 	// Please refer to https://godoc.org/crypto/tls#Config for more information.
 	// (optional, default false)
-	Insecure bool `mapstructure:"insecure"`
+	Insecure bool `mapstructure:"insecure,omitempty"`
 	// InsecureSkipVerify will enable TLS but not verify the certificate.
-	InsecureSkipVerify bool `mapstructure:"insecure_skip_verify"`
+	InsecureSkipVerify bool `mapstructure:"insecure_skip_verify,omitempty"`
 	// ServerName requested by client for virtual hosting.
 	// This sets the ServerName in the TLSConfig. Please refer to
 	// https://godoc.org/crypto/tls#Config for more information. (optional)
-	ServerName string `mapstructure:"server_name_override"`
+	ServerName string `mapstructure:"server_name_override,omitempty"`
 }
 
 // NewDefaultClientConfig creates a new TLSClientSetting with any default values set.
@@ -123,11 +123,11 @@ type ServerConfig struct {
 	// Path to the TLS cert to use by the server to verify a client certificate. (optional)
 	// This sets the ClientCAs and ClientAuth to RequireAndVerifyClientCert in the TLSConfig. Please refer to
 	// https://godoc.org/crypto/tls#Config for more information. (optional)
-	ClientCAFile string `mapstructure:"client_ca_file"`
+	ClientCAFile string `mapstructure:"client_ca_file,omitempty"`
 
 	// Reload the ClientCAs file when it is modified
 	// (optional, default false)
-	ReloadClientCAFile bool `mapstructure:"client_ca_file_reload"`
+	ReloadClientCAFile bool `mapstructure:"client_ca_file_reload,omitempty"`
 }
 
 // NewDefaultServerConfig creates a new TLSServerSetting with any default values set.

internal/e2e/configtls_test.go

@@ -0,0 +1,28 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package e2e
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/config/configtls"
+	"go.opentelemetry.io/collector/confmap"
+)
+
+func TestConfmapMarshalConfigTLS(t *testing.T) {
+	conf := confmap.New()
+	require.NoError(t, conf.Marshal(configtls.NewDefaultConfig()))
+	assert.Equal(t, map[string]any{}, conf.ToStringMap())
+
+	conf = confmap.New()
+	require.NoError(t, conf.Marshal(configtls.NewDefaultClientConfig()))
+	assert.Equal(t, map[string]any{}, conf.ToStringMap())
+
+	conf = confmap.New()
+	require.NoError(t, conf.Marshal(configtls.NewDefaultServerConfig()))
+	assert.Equal(t, map[string]any{}, conf.ToStringMap())
+}