revent end-users from implementing some interfaces (#1575)

"otel/exporters/otlp/otlphttp".Option
"otel/exporters/stdout".Option
"otel/oteltest".Option
"otel/trace".TracerOption
"otel/trace".SpanOption
"otel/trace".EventOption
"otel/trace".LifeCycleOption
"otel/trace".InstrumentationOption
"otel/sdk/resource".Option
"otel/sdk/trace".ParentBasedSamplerOption
"otel/sdk/trace".ReadOnlySpan
"otel/sdk/trace".ReadWriteSpan

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -24,6 +24,21 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Renamed the `otel/label` package to `otel/attribute`. (#1541)
 - Vendor the Jaeger exporter's dependency on Apache Thrift. (#1551)
 - Stagger timestamps in exact aggregator tests. (#1569)
+- Prevent end-users from implementing some interfaces (#1575)
+```
+      "otel/exporters/otlp/otlphttp".Option
+      "otel/exporters/stdout".Option
+      "otel/oteltest".Option
+      "otel/trace".TracerOption
+      "otel/trace".SpanOption
+      "otel/trace".EventOption
+      "otel/trace".LifeCycleOption
+      "otel/trace".InstrumentationOption
+      "otel/sdk/resource".Option
+      "otel/sdk/trace".ParentBasedSamplerOption
+      "otel/sdk/trace".ReadOnlySpan
+      "otel/sdk/trace".ReadWriteSpan
+```
 
 ### Removed
 

exporters/otlp/otlphttp/options.go

@@ -63,6 +63,11 @@ type config struct {
 // Option applies an option to the HTTP driver.
 type Option interface {
 	Apply(*config)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 type endpointOption string
@@ -71,6 +76,8 @@ func (o endpointOption) Apply(cfg *config) {
 	cfg.endpoint = (string)(o)
 }
 
+func (endpointOption) private() {}
+
 // WithEndpoint allows one to set the address of the collector
 // endpoint that the driver will use to send metrics and spans. If
 // unset, it will instead try to use
@@ -86,6 +93,8 @@ func (o compressionOption) Apply(cfg *config) {
 	cfg.compression = (Compression)(o)
 }
 
+func (compressionOption) private() {}
+
 // WithCompression tells the driver to compress the sent data.
 func WithCompression(compression Compression) Option {
 	return (compressionOption)(compression)
@@ -97,6 +106,8 @@ func (o tracesURLPathOption) Apply(cfg *config) {
 	cfg.tracesURLPath = (string)(o)
 }
 
+func (tracesURLPathOption) private() {}
+
 // WithTracesURLPath allows one to override the default URL path used
 // for sending traces. If unset, DefaultTracesPath will be used.
 func WithTracesURLPath(urlPath string) Option {
@@ -109,6 +120,8 @@ func (o metricsURLPathOption) Apply(cfg *config) {
 	cfg.metricsURLPath = (string)(o)
 }
 
+func (metricsURLPathOption) private() {}
+
 // WithMetricsURLPath allows one to override the default URL path used
 // for sending metrics. If unset, DefaultMetricsPath will be used.
 func WithMetricsURLPath(urlPath string) Option {
@@ -121,6 +134,8 @@ func (o maxAttemptsOption) Apply(cfg *config) {
 	cfg.maxAttempts = (int)(o)
 }
 
+func (maxAttemptsOption) private() {}
+
 // WithMaxAttempts allows one to override how many times the driver
 // will try to send the payload in case of retryable errors. If unset,
 // DefaultMaxAttempts will be used.
@@ -134,6 +149,8 @@ func (o backoffOption) Apply(cfg *config) {
 	cfg.backoff = (time.Duration)(o)
 }
 
+func (backoffOption) private() {}
+
 // WithBackoff tells the driver to use the duration as a base of the
 // exponential backoff strategy. If unset, DefaultBackoff will be
 // used.
@@ -147,6 +164,8 @@ func (o *tlsClientConfigOption) Apply(cfg *config) {
 	cfg.tlsCfg = (*tls.Config)(o)
 }
 
+func (*tlsClientConfigOption) private() {}
+
 // WithTLSClientConfig can be used to set up a custom TLS
 // configuration for the client used to send payloads to the
 // collector. Use it if you want to use a custom certificate.
@@ -160,6 +179,8 @@ func (insecureOption) Apply(cfg *config) {
 	cfg.insecure = true
 }
 
+func (insecureOption) private() {}
+
 // WithInsecure tells the driver to connect to the collector using the
 // HTTP scheme, instead of HTTPS.
 func WithInsecure() Option {
@@ -172,6 +193,8 @@ func (o headersOption) Apply(cfg *config) {
 	cfg.headers = (map[string]string)(o)
 }
 
+func (headersOption) private() {}
+
 // WithHeaders allows one to tell the driver to send additional HTTP
 // headers with the payloads. Specifying headers like Content-Length,
 // Content-Encoding and Content-Type may result in a broken driver.

exporters/stdout/config.go

@@ -74,6 +74,11 @@ func NewConfig(options ...Option) (Config, error) {
 type Option interface {
 	// Apply option value to Config.
 	Apply(*Config)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 // WithWriter sets the export stream destination.
@@ -89,6 +94,8 @@ func (o writerOption) Apply(config *Config) {
 	config.Writer = o.W
 }
 
+func (writerOption) private() {}
+
 // WithPrettyPrint sets the export stream format to use JSON.
 func WithPrettyPrint() Option {
 	return prettyPrintOption(true)
@@ -100,6 +107,8 @@ func (o prettyPrintOption) Apply(config *Config) {
 	config.PrettyPrint = bool(o)
 }
 
+func (prettyPrintOption) private() {}
+
 // WithoutTimestamps sets the export stream to not include timestamps.
 func WithoutTimestamps() Option {
 	return timestampsOption(false)
@@ -111,6 +120,8 @@ func (o timestampsOption) Apply(config *Config) {
 	config.Timestamps = bool(o)
 }
 
+func (timestampsOption) private() {}
+
 // WithLabelEncoder sets the label encoder used in export.
 func WithLabelEncoder(enc attribute.Encoder) Option {
 	return labelEncoderOption{enc}
@@ -124,6 +135,8 @@ func (o labelEncoderOption) Apply(config *Config) {
 	config.LabelEncoder = o.LabelEncoder
 }
 
+func (labelEncoderOption) private() {}
+
 // WithoutTraceExport disables all trace exporting.
 func WithoutTraceExport() Option {
 	return disableTraceExportOption(true)
@@ -135,6 +148,8 @@ func (o disableTraceExportOption) Apply(config *Config) {
 	config.DisableTraceExport = bool(o)
 }
 
+func (disableTraceExportOption) private() {}
+
 // WithoutMetricExport disables all metric exporting.
 func WithoutMetricExport() Option {
 	return disableMetricExportOption(true)
@@ -145,3 +160,5 @@ type disableMetricExportOption bool
 func (o disableMetricExportOption) Apply(config *Config) {
 	config.DisableMetricExport = bool(o)
 }
+
+func (disableMetricExportOption) private() {}

internal/tools/go.sum

@@ -540,7 +540,6 @@ golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200519105757-fe76b779f299/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200602225109-6fdc65e7d980/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78 h1:nVuTkr9L6Bq62qpUqKo/RnZCFfzDBL0bYo6w9OJUqZY=
 golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -604,7 +603,6 @@ golang.org/x/tools v0.0.0-20201118003311-bd56c0adb394/go.mod h1:emZCQorbCU4vsT4f
 golang.org/x/tools v0.0.0-20201230224404-63754364767c/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.0.0-20210101214203-2dba1e4ea05c/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.0.0-20210102185154-773b96fafca2/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
-golang.org/x/tools v0.0.0-20210106214847-113979e3529a h1:CB3a9Nez8M13wwlr/E2YtwoU+qYHKfC+JrDa45RXXoQ=
 golang.org/x/tools v0.0.0-20210106214847-113979e3529a/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.1.0 h1:po9/4sTYwZU9lPhi1tOrb4hCv3qrhiQ77LZfGa2OjwY=
 golang.org/x/tools v0.1.0/go.mod h1:xkSsbof2nBLbhDlRMhhhyNLN/zl3eTqcnHD5viDpcZ0=

oteltest/config.go

@@ -63,9 +63,19 @@ func newConfig(opts ...Option) config {
 // Option applies an option to a config.
 type Option interface {
 	Apply(*config)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
+type option struct{}
+
+func (option) private() {}
+
 type spanContextFuncOption struct {
+	option
 	SpanContextFunc func(context.Context) trace.SpanContext
 }
 
@@ -76,10 +86,11 @@ func (o spanContextFuncOption) Apply(c *config) {
 // WithSpanContextFunc sets the SpanContextFunc used to generate a new Spans
 // context from a parent SpanContext.
 func WithSpanContextFunc(f func(context.Context) trace.SpanContext) Option {
-	return spanContextFuncOption{f}
+	return spanContextFuncOption{SpanContextFunc: f}
 }
 
 type spanRecorderOption struct {
+	option
 	SpanRecorder *SpanRecorder
 }
 
@@ -90,7 +101,7 @@ func (o spanRecorderOption) Apply(c *config) {
 // WithSpanRecorder sets the SpanRecorder to use with the TracerProvider for
 // testing.
 func WithSpanRecorder(sr *SpanRecorder) Option {
-	return spanRecorderOption{sr}
+	return spanRecorderOption{SpanRecorder: sr}
 }
 
 // SpanRecorder performs operations to record a span as it starts and ends.

sdk/resource/config.go

@@ -42,8 +42,17 @@ type config struct {
 type Option interface {
 	// Apply sets the Option value of a config.
 	Apply(*config)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
+type option struct{}
+
+func (option) private() {}
+
 // WithAttributes adds attributes to the configured Resource.
 func WithAttributes(attributes ...attribute.KeyValue) Option {
 	return WithDetectors(detectAttributes{attributes})
@@ -59,10 +68,11 @@ func (d detectAttributes) Detect(context.Context) (*Resource, error) {
 
 // WithDetectors adds detectors to be evaluated for the configured resource.
 func WithDetectors(detectors ...Detector) Option {
-	return detectorsOption{detectors}
+	return detectorsOption{detectors: detectors}
 }
 
 type detectorsOption struct {
+	option
 	detectors []Detector
 }
 
@@ -74,10 +84,11 @@ func (o detectorsOption) Apply(cfg *config) {
 // WithTelemetrySDK overrides the builtin `telemetry.sdk.*`
 // attributes.  Use nil to disable these attributes entirely.
 func WithTelemetrySDK(d Detector) Option {
-	return telemetrySDKOption{d}
+	return telemetrySDKOption{Detector: d}
 }
 
 type telemetrySDKOption struct {
+	option
 	Detector
 }
 
@@ -89,10 +100,11 @@ func (o telemetrySDKOption) Apply(cfg *config) {
 // WithHost overrides the builtin `host.*` attributes.  Use nil to
 // disable these attributes entirely.
 func WithHost(d Detector) Option {
-	return hostOption{d}
+	return hostOption{Detector: d}
 }
 
 type hostOption struct {
+	option
 	Detector
 }
 
@@ -104,10 +116,11 @@ func (o hostOption) Apply(cfg *config) {
 // WithFromEnv overrides the builtin detector for
 // OTEL_RESOURCE_ATTRIBUTES.  Use nil to disable environment checking.
 func WithFromEnv(d Detector) Option {
-	return fromEnvOption{d}
+	return fromEnvOption{Detector: d}
 }
 
 type fromEnvOption struct {
+	option
 	Detector
 }
 
@@ -122,7 +135,9 @@ func WithoutBuiltin() Option {
 	return noBuiltinOption{}
 }
 
-type noBuiltinOption struct{}
+type noBuiltinOption struct {
+	option
+}
 
 // Apply implements Option.
 func (o noBuiltinOption) Apply(cfg *config) {

sdk/trace/sampling.go

@@ -190,6 +190,11 @@ type config struct {
 // ParentBasedSamplerOption configures the sampler for a particular sampling case.
 type ParentBasedSamplerOption interface {
 	Apply(*config)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 // WithRemoteParentSampled sets the sampler for the case of sampled remote parent.
@@ -205,6 +210,8 @@ func (o remoteParentSampledOption) Apply(config *config) {
 	config.remoteParentSampled = o.s
 }
 
+func (remoteParentSampledOption) private() {}
+
 // WithRemoteParentNotSampled sets the sampler for the case of remote parent
 // which is not sampled.
 func WithRemoteParentNotSampled(s Sampler) ParentBasedSamplerOption {
@@ -219,6 +226,8 @@ func (o remoteParentNotSampledOption) Apply(config *config) {
 	config.remoteParentNotSampled = o.s
 }
 
+func (remoteParentNotSampledOption) private() {}
+
 // WithLocalParentSampled sets the sampler for the case of sampled local parent.
 func WithLocalParentSampled(s Sampler) ParentBasedSamplerOption {
 	return localParentSampledOption{s}
@@ -232,6 +241,8 @@ func (o localParentSampledOption) Apply(config *config) {
 	config.localParentSampled = o.s
 }
 
+func (localParentSampledOption) private() {}
+
 // WithLocalParentNotSampled sets the sampler for the case of local parent
 // which is not sampled.
 func WithLocalParentNotSampled(s Sampler) ParentBasedSamplerOption {
@@ -246,6 +257,8 @@ func (o localParentNotSampledOption) Apply(config *config) {
 	config.localParentNotSampled = o.s
 }
 
+func (localParentNotSampledOption) private() {}
+
 func (pb parentBased) ShouldSample(p SamplingParameters) SamplingResult {
 	if p.ParentContext.IsValid() {
 		if p.HasRemoteParent {

sdk/trace/span.go

@@ -60,6 +60,11 @@ type ReadOnlySpan interface {
 	InstrumentationLibrary() instrumentation.Library
 	Resource() *resource.Resource
 	Snapshot() *export.SpanSnapshot
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 // ReadWriteSpan exposes the same methods as trace.Span and in addition allows
@@ -505,6 +510,8 @@ func (s *span) addDroppedAttributeCount(delta int) {
 	atomic.AddInt64(&s.droppedAttributeCount, int64(delta))
 }
 
+func (*span) private() {}
+
 func startSpanInternal(ctx context.Context, tr *tracer, name string, parent trace.SpanContext, remoteParent bool, o *trace.SpanConfig) *span {
 	span := &span{}
 	span.spanContext = parent

trace/config.go

@@ -39,6 +39,11 @@ func NewTracerConfig(options ...TracerOption) *TracerConfig {
 // TracerOption applies an option to a TracerConfig.
 type TracerOption interface {
 	ApplyTracer(*TracerConfig)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 // SpanConfig is a group of options for a Span.
@@ -74,6 +79,11 @@ func NewSpanConfig(options ...SpanOption) *SpanConfig {
 // SpanOption applies an option to a SpanConfig.
 type SpanOption interface {
 	ApplySpan(*SpanConfig)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 // NewEventConfig applies all the EventOptions to a returned SpanConfig. If no
@@ -94,6 +104,11 @@ func NewEventConfig(options ...EventOption) *SpanConfig {
 // EventOption applies span event options to a SpanConfig.
 type EventOption interface {
 	ApplyEvent(*SpanConfig)
+
+	// A private method to prevent users implementing the
+	// interface and so future additions to it will not
+	// violate compatibility.
+	private()
 }
 
 // LifeCycleOption applies span life-cycle options to a SpanConfig. These
@@ -108,6 +123,7 @@ type attributeSpanOption []attribute.KeyValue
 
 func (o attributeSpanOption) ApplySpan(c *SpanConfig)  { o.apply(c) }
 func (o attributeSpanOption) ApplyEvent(c *SpanConfig) { o.apply(c) }
+func (attributeSpanOption) private()                   {}
 func (o attributeSpanOption) apply(c *SpanConfig) {
 	c.Attributes = append(c.Attributes, []attribute.KeyValue(o)...)
 }
@@ -129,6 +145,7 @@ type timestampSpanOption time.Time
 
 func (o timestampSpanOption) ApplySpan(c *SpanConfig)  { o.apply(c) }
 func (o timestampSpanOption) ApplyEvent(c *SpanConfig) { o.apply(c) }
+func (timestampSpanOption) private()                   {}
 func (o timestampSpanOption) apply(c *SpanConfig)      { c.Timestamp = time.Time(o) }
 
 // WithTimestamp sets the time of a Span life-cycle moment (e.g. started,
@@ -140,6 +157,7 @@ func WithTimestamp(t time.Time) LifeCycleOption {
 type linksSpanOption []Link
 
 func (o linksSpanOption) ApplySpan(c *SpanConfig) { c.Links = append(c.Links, []Link(o)...) }
+func (linksSpanOption) private()                  {}
 
 // WithLinks adds links to a Span. The links are added to the existing Span
 // links, i.e. this does not overwrite.
@@ -150,6 +168,7 @@ func WithLinks(links ...Link) SpanOption {
 type recordSpanOption bool
 
 func (o recordSpanOption) ApplySpan(c *SpanConfig) { c.Record = bool(o) }
+func (recordSpanOption) private()                  {}
 
 // WithRecord specifies that the span should be recorded. It is important to
 // note that implementations may override this option, i.e. if the span is a
@@ -161,6 +180,7 @@ func WithRecord() SpanOption {
 type newRootSpanOption bool
 
 func (o newRootSpanOption) ApplySpan(c *SpanConfig) { c.NewRoot = bool(o) }
+func (newRootSpanOption) private()                  {}
 
 // WithNewRoot specifies that the Span should be treated as a root Span. Any
 // existing parent span context will be ignored when defining the Span's trace
@@ -172,6 +192,7 @@ func WithNewRoot() SpanOption {
 type spanKindSpanOption SpanKind
 
 func (o spanKindSpanOption) ApplySpan(c *SpanConfig) { c.SpanKind = SpanKind(o) }
+func (o spanKindSpanOption) private()                {}
 
 // WithSpanKind sets the SpanKind of a Span.
 func WithSpanKind(kind SpanKind) SpanOption {
@@ -194,3 +215,5 @@ type instrumentationVersionOption string
 func (i instrumentationVersionOption) ApplyTracer(config *TracerConfig) {
 	config.InstrumentationVersion = string(i)
 }
+
+func (instrumentationVersionOption) private() {}