Fix linter issue, document remote_sampling change

CHANGELOG.md

@@ -28,7 +28,7 @@ Main (unreleased)
 - Rename `discovery.file` to `local.file_match` to make it more clear that it
   discovers file on the local filesystem, and so it doesn't get confused with
   Prometheus' file discovery. (@rfratto)
-  
+
 - In the traces subsystem for Static mode, some metrics are removed and others are renamed. (@ptodev)
   - Removed metrics:
     - "blackbox_exporter_config_last_reload_success_timestamp_seconds" (gauge)
@@ -54,6 +54,8 @@ Main (unreleased)
     - "traces_receiver_accepted_spans" is renamed to "traces_receiver_refused_spans_total"
     - "traces_exporter_sent_metric_points" is renamed to "traces_exporter_sent_metric_points_total"
 
+- The `remote_sampling` block has been removed from `otelcol.receiver.jaeger`. (@ptodev)
+
 ### Features
 
 - The Pyroscope scrape component computes and sends delta profiles automatically when required to reduce bandwidth usage. (@cyriltovena)

component/otelcol/processor/tail_sampling/tail_sampling_test.go

@@ -36,6 +36,35 @@ func TestBadRiverConfig(t *testing.T) {
 	require.Error(t, river.Unmarshal([]byte(exampleBadRiverConfig), &args), "num_traces must be greater than zero")
 }
 
+func TestBadRiverConfigErrorMode(t *testing.T) {
+	exampleBadRiverConfig := `
+    decision_wait               = "10s"
+    num_traces                  = 5
+    expected_new_traces_per_sec = 10
+    policy {
+      name = "test-policy-1"
+      type = "ottl_condition"
+      ottl_condition {
+        error_mode = ""
+        span = [
+          "attributes[\"test_attr_key_1\"] == \"test_attr_val_1\"",
+          "attributes[\"test_attr_key_2\"] != \"test_attr_val_1\"",
+        ]
+        spanevent = [
+          "name != \"test_span_event_name\"",
+          "attributes[\"test_event_attr_key_2\"] != \"test_event_attr_val_1\"",
+        ]
+      }
+    }
+    output { 
+	    // no-op: will be overridden by test code.
+    }
+`
+
+	var args Arguments
+	require.ErrorContains(t, river.Unmarshal([]byte(exampleBadRiverConfig), &args), "\"\" unknown error mode")
+}
+
 func TestBadOtelConfig(t *testing.T) {
 	var exampleBadOtelConfig = `
     decision_wait               = "10s"

component/otelcol/processor/tail_sampling/types.go

@@ -246,18 +246,36 @@ var (
 
 // Validate implements river.Validator.
 func (e *ErrorMode) Validate() error {
+	if e == nil {
+		return nil
+	}
+
 	var ottlError ottl.ErrorMode
 	return ottlError.UnmarshalText([]byte(string(*e)))
 }
 
 // Convert the River type to the Otel type
 func (e *ErrorMode) Convert() ottl.ErrorMode {
+	if e == nil || *e == "" {
+		return ottl.ErrorMode("")
+	}
+
 	var ottlError ottl.ErrorMode
-	ottlError.UnmarshalText([]byte(string(*e)))
+	err := ottlError.UnmarshalText([]byte(string(*e)))
+
+	//TODO: Rework this to return an error instead of panicking
+	if err != nil {
+		panic(err)
+	}
+
 	return ottlError
 }
 
 func (e *ErrorMode) UnmarshalText(text []byte) error {
+	if e == nil {
+		return nil
+	}
+
 	str := ErrorMode(strings.ToLower(string(text)))
 	switch str {
 	case ErrorModeIgnore, ErrorModePropagate:
@@ -434,6 +452,7 @@ func (andSubPolicyConfig AndSubPolicyConfig) Convert() tsp.AndSubPolicyCfg {
 func mustDecodeMapStructure(source map[string]interface{}, otelConfig interface{}) {
 	err := mapstructure.Decode(source, otelConfig)
 
+	//TODO: Rework this to return an error instead of panicking
 	if err != nil {
 		panic(err)
 	}

docs/sources/flow/upgrade-guide.md

@@ -52,6 +52,11 @@ Additional `instrumentation_scope` information will be added to the OTLP log sig
 The `/` HTTP endpoint was the same as the `/sampling` endpoint. The `/sampling` endpoint is still functional.
 The change was made in PR [#18070](https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/18070) of opentelemetry-collector-contrib. 
 
+### The `remote_sampling` block has been removed from `otelcol.receiver.jaeger`
+
+The `remote_sampling` block in `otelcol.receiver.jaeger` has been an undocumented no-op configuration for some time, and has now been removed. 
+Customers are advised to use `otelcol.extension.jaeger_remote_sampling` instead.
+
 ## v0.35
 
 ### Breaking change: `auth` and `version` attributes from `walk_params` block of `prometheus.exporter.snmp` have been removed