fix loki.source.file docs re legacy positions file (#3830)

Author: thampiotr

docs/sources/reference/components/loki/loki.source.file.md

@@ -52,9 +52,8 @@ You can use the `tail_from_end` argument when you want to tail a large file with
 When set to true, only new logs are read, ignoring the existing ones.
 
 {{< admonition type="note" >}}
-The `legacy_positions_file` argument is used when you are transitioning from legacy. The legacy positions file is rewritten into the new format.
-This operation only occurs if the positions file doesn't exist and the `legacy_positions_file` is valid.
-After the configuration is successfully converted, the `legacy_positions_file` is deleted.
+The `legacy_positions_file` argument is used when you are transitioning from legacy. The legacy positions file is converted to the new format.
+This operation only occurs if the new positions file doesn't exist and the `legacy_positions_file` is valid.
 If you add any labels before `loki.source.file`, then the positions file conversion won't work.
 The legacy positions file didn't have a concept of labels in the positions file, so the conversion assumes no labels.
 {{< /admonition >}}

internal/component/common/loki/positions/positions.go

@@ -15,8 +15,9 @@ import (
 	"time"
 
 	"github.com/go-kit/log"
-	"github.com/grafana/alloy/internal/runtime/logging/level"
 	yaml "gopkg.in/yaml.v2"
+
+	"github.com/grafana/alloy/internal/runtime/logging/level"
 )
 
 const (
@@ -106,14 +107,15 @@ type LegacyFile struct {
 // 2. There is a file at the legacy path and that it is valid yaml
 func ConvertLegacyPositionsFile(legacyPath, newPath string, l log.Logger) {
 	legacyPositions := readLegacyFile(legacyPath, l)
-	// LegacyPositions did not exist or was invalid so return.
+	// legacyPositions did not exist or was invalid so return.
 	if legacyPositions == nil {
+		level.Info(l).Log("msg", "will not convert the legacy positions file as it is not valid or does not exist", "legacy_path", legacyPath)
 		return
 	}
 	fi, err := os.Stat(newPath)
 	// If the newpath exists, then don't convert.
 	if err == nil && fi.Size() > 0 {
-		level.Info(l).Log("msg", "new positions file already exists", "path", newPath)
+		level.Info(l).Log("msg", "will not convert the legacy positions file as the new positions file already exists", "path", newPath)
 		return
 	}
 
@@ -125,11 +127,11 @@ func ConvertLegacyPositionsFile(legacyPath, newPath string, l log.Logger) {
 			Labels: "{}",
 		}] = v
 	}
-	// After conversion remove the file.
 	err = writePositionFile(newPath, newPositions)
 	if err != nil {
-		level.Error(l).Log("msg", "error writing new positions file from legacy", "path", newPath, "error", err)
+		level.Error(l).Log("msg", "error writing new positions file converted from legacy", "path", newPath, "error", err)
 	}
+	level.Info(l).Log("msg", "successfully converted legacy positions file to the new format", "path", newPath, "legacy_path", legacyPath)
 }
 
 func readLegacyFile(legacyPath string, l log.Logger) *LegacyFile {