config: support both file path and inline settings

Restore support for specifying pii, filter, and summary settings as
either a simple string file path to a YAML file, or as an inline
object/map. The private `any`-typed fields receive whichever form
mapstructure decodes from the collector config, and resolveAnyField()
dispatches to the appropriate parser during Validate().

When the value is a string, the existing parseYmlFile() path is used
to read and parse the YAML file. When it is a map, mapstructure
decodes it directly into the typed struct. This preserves backwards
compatibility with configs that reference separate .yml files while
also supporting the inline configuration introduced in previous
commits.

Add tests for the file-path code path covering valid files, missing
files, and malformed content for all three settings types.

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

Author: mjcheetham

Docs/Examples/DebugDump/config.yml

@@ -16,6 +16,9 @@
 #
 # You can also use ${file:PATH} to reference an external YAML file,
 # e.g.: filter: "${file:/path/to/filter.yml}"
+#
+# For backwards compatibility, you can also specify a plain file path:
+# e.g.: filter: "/path/to/filter.yml"
 
 receivers:
   trace2receiver:

Docs/Examples/ExportToAzureMonitor/config.yml

@@ -15,6 +15,9 @@
 #
 # You can also use ${file:PATH} to reference an external YAML file,
 # e.g.: filter: "${file:/path/to/filter.yml}"
+#
+# For backwards compatibility, you can also specify a plain file path:
+# e.g.: filter: "/path/to/filter.yml"
 
 receivers:
   trace2receiver:

Docs/config-filter-settings.md

@@ -11,6 +11,11 @@ The filter settings are specified inline under the
 parameter in the main `config.yml` file.  Alternatively, you can use
 the `${file:PATH}` syntax to reference an external YAML file.
 
+For backwards compatibility, you can also specify a plain file path
+string (without the `${file:}` wrapper) as the value of the `filter`
+field, and the receiver will read and parse the YAML file at that
+path.
+
 
 
 ## Smart Filtering using Detail Levels, Rulesets, and Repo Nicknames

Docs/config-pii-settings.md

@@ -14,6 +14,11 @@ The PII settings are specified inline under the
 parameter in the main `config.yml` file.  Alternatively, you can use
 the `${file:PATH}` syntax to reference an external YAML file.
 
+For backwards compatibility, you can also specify a plain file path
+string (without the `${file:}` wrapper) as the value of the `pii`
+field, and the receiver will read and parse the YAML file at that
+path.
+
 ## PII Settings Syntax
 
 The PII settings have the following syntax:

Docs/configure-custom-collector.md

@@ -69,7 +69,8 @@ receivers:
 ```
 
 If you prefer to keep the `pii`, `filter`, or `summary` configuration
-in a separate file, you can use the `${file:PATH}` syntax:
+in a separate file, you can use the `${file:PATH}` syntax or specify
+a simple file path string:
 
 ```
 receivers:
@@ -80,6 +81,18 @@ receivers:
     filter: "${file:/usr/local/my-collector/filter.yml}"
 ```
 
+For backwards compatibility, you can also specify a plain file path
+without the `${file:}` wrapper:
+
+```
+receivers:
+  trace2receiver:
+    socket: "/usr/local/my-collector/trace2.socket"
+    pipe:   "//./pipe/my-collector.pipe"
+    pii:    "/usr/local/my-collector/pii.yml"
+    filter: "/usr/local/my-collector/filter.yml"
+```
+
 ### `<unix-domain-socket-pathname>` (Required on Unix)
 
 The pathname will be used on Linux and macOS hosts to create a Unix
@@ -129,6 +142,9 @@ $ git config --system trace2.eventtarget "//./pipe/my-collector.pipe"
 Inline PII settings controlling privacy-related feature flags.
 This is optional.  These features are disabled by default.
 
+For backwards compatibility, this field also accepts a simple string
+containing a file path to a YAML file with the PII settings.
+
 See [config PII settings](./config-pii-settings.md) for details.
 
 ### `filter` (Optional)
@@ -137,4 +153,16 @@ Inline filter settings controlling the verbosity of the
 generated OTEL telemetry data.  This is optional.  If omitted,
 summary-level telemetry will be emitted.
 
+For backwards compatibility, this field also accepts a simple string
+containing a file path to a YAML file with the filter settings.
+
 See [config filter settings](./config-filter-settings.md) for details.
+
+### `summary` (Optional)
+
+Inline summary settings controlling aggregated metrics from trace2
+events.  This is optional.  If omitted, no summary metrics will be
+emitted.
+
+For backwards compatibility, this field also accepts a simple string
+containing a file path to a YAML file with the summary settings.

config.go

@@ -5,12 +5,18 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+
+	"github.com/mitchellh/mapstructure"
 )
 
-// Note: The `pii`, `filter`, and `summary` fields accept inline
-// YAML configuration.  If you prefer to keep the configuration
-// in a separate file, use the `${file:PATH}` syntax to reference
-// an external YAML file.
+// Note: The `pii`, `filter`, and `summary` fields accept either:
+//   - inline YAML/JSON configuration (an object/map), or
+//   - a string containing a file path to a YAML file.
+//
+// This for backwards compatibility with the original design of the
+// config where these were only allowed to be file paths.
+// You can continue to use a simple string, or the built-in ${file}
+// syntax to specify a file path if inline config is not convenient.
 
 // `Config` represents the complete configuration settings for
 // an individual receiver declaration from the `config.yaml`.
@@ -52,13 +58,16 @@ type Config struct {
 
 	// PII settings control whether possibly GDPR-sensitive fields
 	// are included in the telemetry output.
-	Pii *PiiSettings `mapstructure:"pii"`
+	rawPii any `mapstructure:"pii"`
+	Pii    *PiiSettings
 
 	// Filter settings control how the OTLP output is filtered.
-	Filter *FilterSettings `mapstructure:"filter"`
+	rawFilter any `mapstructure:"filter"`
+	Filter    *FilterSettings
 
 	// Summary settings control aggregated metrics from trace2 events.
-	Summary *SummarySettings `mapstructure:"summary"`
+	rawSummary any `mapstructure:"summary"`
+	Summary    *SummarySettings
 }
 
 // `Validate()` checks if the receiver configuration is valid.
@@ -104,12 +113,33 @@ func (cfg *Config) Validate() error {
 		cfg.UnixSocketPath = path
 	}
 
+	if cfg.rawPii != nil {
+		cfg.Pii, err = resolveAnyField(cfg.rawPii, parsePiiFromBuffer)
+		if err != nil {
+			return fmt.Errorf("pii: %w", err)
+		}
+	}
+
+	if cfg.rawFilter != nil {
+		cfg.Filter, err = resolveAnyField(cfg.rawFilter, parseFilterSettingsFromBuffer)
+		if err != nil {
+			return fmt.Errorf("filter: %w", err)
+		}
+	}
+
 	if cfg.Filter != nil {
 		if err = cfg.Filter.validate(); err != nil {
 			return err
 		}
 	}
 
+	if cfg.rawSummary != nil {
+		cfg.Summary, err = resolveAnyField(cfg.rawSummary, parseSummarySettingsFromBuffer)
+		if err != nil {
+			return fmt.Errorf("summary: %w", err)
+		}
+	}
+
 	if cfg.Summary != nil {
 		if err = cfg.Summary.validate(); err != nil {
 			return err
@@ -119,6 +149,40 @@ func (cfg *Config) Validate() error {
 	return nil
 }
 
+// resolveAnyField handles a config field that may be either:
+//   - nil: the field was not specified
+//   - a string: a file path to a YAML file to parse
+//   - a map: inline configuration to decode into the target struct
+func resolveAnyField[T MyYmlFileTypes](raw any, parseFn MyYmlParseBufferFn[T]) (*T, error) {
+	if raw == nil {
+		return nil, nil
+	}
+
+	switch v := raw.(type) {
+	case string:
+		if len(v) == 0 {
+			return nil, nil
+		}
+		return parseYmlFile(v, parseFn)
+
+	default:
+		// Assume it's a map/object from inline configuration.
+		// Use mapstructure to decode the raw value into the typed struct.
+		p := new(T)
+		decoder, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
+			Result:  p,
+			TagName: "mapstructure",
+		})
+		if err != nil {
+			return nil, fmt.Errorf("could not create decoder: %w", err)
+		}
+		if err = decoder.Decode(v); err != nil {
+			return nil, fmt.Errorf("could not decode inline config: %w", err)
+		}
+		return p, nil
+	}
+}
+
 // Require (the backslash spelling of) `//./pipe/<pipename>` but allow
 // `<pipename>` as an alias for the full spelling.  Complain if given a
 // regular UNC or drive letter pathname.

config_test.go

@@ -1,10 +1,13 @@
 package trace2receiver
 
 import (
+	"os"
+	"path/filepath"
 	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 // Test Validate with minimal valid config on Windows
@@ -269,6 +272,127 @@ func Test_Config_Validate_WithCommandControlEnabled(t *testing.T) {
 	assert.NoError(t, err)
 }
 
+// Test Validate with PII settings from file path
+func Test_Config_Validate_WithPiiFilePath(t *testing.T) {
+	tmpDir := t.TempDir()
+	piiPath := filepath.Join(tmpDir, "pii.yml")
+	piiContent := `
+include:
+  hostname: true
+  username: false
+`
+	err := os.WriteFile(piiPath, []byte(piiContent), 0644)
+	require.NoError(t, err)
+
+	cfg := createMinimalValidConfig()
+	cfg.rawPii = piiPath
+
+	err = cfg.Validate()
+	assert.NoError(t, err)
+	assert.NotNil(t, cfg.Pii)
+	assert.True(t, cfg.Pii.Include.Hostname)
+	assert.False(t, cfg.Pii.Include.Username)
+}
+
+// Test Validate with invalid PII file path
+func Test_Config_Validate_WithInvalidPiiFilePath(t *testing.T) {
+	cfg := createMinimalValidConfig()
+	cfg.rawPii = "/nonexistent/pii.yml"
+
+	err := cfg.Validate()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "pii:")
+}
+
+// Test Validate with filter settings from file path
+func Test_Config_Validate_WithFilterFilePath(t *testing.T) {
+	tmpDir := t.TempDir()
+	filterPath := filepath.Join(tmpDir, "filter.yml")
+	filterContent := `
+defaults:
+  ruleset: "dl:verbose"
+`
+	err := os.WriteFile(filterPath, []byte(filterContent), 0644)
+	require.NoError(t, err)
+
+	cfg := createMinimalValidConfig()
+	cfg.rawFilter = filterPath
+
+	err = cfg.Validate()
+	assert.NoError(t, err)
+	assert.NotNil(t, cfg.Filter)
+}
+
+// Test Validate with invalid filter file path
+func Test_Config_Validate_WithInvalidFilterFilePath(t *testing.T) {
+	cfg := createMinimalValidConfig()
+	cfg.rawFilter = "/nonexistent/filter.yml"
+
+	err := cfg.Validate()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "filter:")
+}
+
+// Test Validate with summary settings from file path
+func Test_Config_Validate_WithSummaryFilePath(t *testing.T) {
+	tmpDir := t.TempDir()
+	summaryPath := filepath.Join(tmpDir, "summary.yml")
+	summaryContent := `
+message_patterns:
+  - prefix: "error:"
+    field_name: "error_count"
+  - prefix: "warning:"
+    field_name: "warning_count"
+
+region_timers:
+  - category: "index"
+    label: "do_read_index"
+    count_field: "index_read_count"
+    time_field: "index_read_time"
+`
+	err := os.WriteFile(summaryPath, []byte(summaryContent), 0644)
+	require.NoError(t, err)
+
+	cfg := createMinimalValidConfig()
+	cfg.rawSummary = summaryPath
+
+	err = cfg.Validate()
+	assert.NoError(t, err)
+	assert.NotNil(t, cfg.Summary)
+	assert.Equal(t, 2, len(cfg.Summary.MessagePatterns))
+	assert.Equal(t, 1, len(cfg.Summary.RegionTimers))
+}
+
+// Test Validate with invalid summary file path
+func Test_Config_Validate_WithInvalidSummaryFilePath(t *testing.T) {
+	cfg := createMinimalValidConfig()
+	cfg.rawSummary = "/nonexistent/summary.yml"
+
+	err := cfg.Validate()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "summary:")
+}
+
+// Test Validate with malformed summary from file path
+func Test_Config_Validate_WithMalformedSummaryFilePath(t *testing.T) {
+	tmpDir := t.TempDir()
+	summaryPath := filepath.Join(tmpDir, "summary.yml")
+	summaryContent := `
+message_patterns:
+  - prefix: "error:"
+    field_name: ""
+`
+	err := os.WriteFile(summaryPath, []byte(summaryContent), 0644)
+	require.NoError(t, err)
+
+	cfg := createMinimalValidConfig()
+	cfg.rawSummary = summaryPath
+
+	err = cfg.Validate()
+	assert.Error(t, err)
+	assert.Contains(t, err.Error(), "field_name cannot be empty")
+}
+
 // Helper function to create a minimal valid config for the current platform
 func createMinimalValidConfig() *Config {
 	if runtime.GOOS == "windows" {