From be9fefb8a8f1c24ecf43d4abbaa019447062a661 Mon Sep 17 00:00:00 2001
From: Daniel Jaglowski <jaglows3@gmail.com>
Date: Fri, 22 Sep 2023 10:08:52 -0600
Subject: [PATCH] [chore][pkg/stanza] Minor cleanup in split package (#27075)

---
 pkg/stanza/split/split.go      | 42 +++++++++++++++++++---------------
 pkg/stanza/split/split_test.go | 20 ++++++++--------
 2 files changed, 33 insertions(+), 29 deletions(-)

diff --git a/pkg/stanza/split/split.go b/pkg/stanza/split/split.go
index b5883c14841f..310a8f031c66 100644
--- a/pkg/stanza/split/split.go
+++ b/pkg/stanza/split/split.go
@@ -20,33 +20,38 @@ type Config struct {
 }
 
 // Func will return a bufio.SplitFunc based on the config
-func (c Config) Func(enc encoding.Encoding, flushAtEOF bool, maxLogSize int) (splitFunc bufio.SplitFunc, err error) {
-	switch {
-	case c.LineEndPattern != "" && c.LineStartPattern != "":
-		return nil, fmt.Errorf("only one of line_start_pattern or line_end_pattern can be set")
-	case enc == encoding.Nop && (c.LineEndPattern != "" || c.LineStartPattern != ""):
-		return nil, fmt.Errorf("line_start_pattern or line_end_pattern should not be set when using nop encoding")
-	case enc == encoding.Nop:
-		return NoSplitFunc(maxLogSize), nil
-	case c.LineEndPattern == "" && c.LineStartPattern == "":
-		splitFunc, err = NewlineSplitFunc(enc, flushAtEOF)
-		if err != nil {
-			return nil, err
+func (c Config) Func(enc encoding.Encoding, flushAtEOF bool, maxLogSize int) (bufio.SplitFunc, error) {
+	if enc == encoding.Nop {
+		if c.LineEndPattern != "" {
+			return nil, fmt.Errorf("line_end_pattern should not be set when using nop encoding")
+		}
+		if c.LineStartPattern != "" {
+			return nil, fmt.Errorf("line_start_pattern should not be set when using nop encoding")
 		}
-	case c.LineEndPattern != "":
+		return NoSplitFunc(maxLogSize), nil
+	}
+
+	if c.LineEndPattern == "" && c.LineStartPattern == "" {
+		return NewlineSplitFunc(enc, flushAtEOF)
+	}
+
+	if c.LineEndPattern != "" && c.LineStartPattern == "" {
 		re, err := regexp.Compile("(?m)" + c.LineEndPattern)
 		if err != nil {
 			return nil, fmt.Errorf("compile line end regex: %w", err)
 		}
-		splitFunc = LineEndSplitFunc(re, c.OmitPattern, flushAtEOF)
-	case c.LineStartPattern != "":
+		return LineEndSplitFunc(re, c.OmitPattern, flushAtEOF), nil
+	}
+
+	if c.LineEndPattern == "" && c.LineStartPattern != "" {
 		re, err := regexp.Compile("(?m)" + c.LineStartPattern)
 		if err != nil {
 			return nil, fmt.Errorf("compile line start regex: %w", err)
 		}
-		splitFunc = LineStartSplitFunc(re, c.OmitPattern, flushAtEOF)
+		return LineStartSplitFunc(re, c.OmitPattern, flushAtEOF), nil
 	}
-	return splitFunc, nil
+
+	return nil, fmt.Errorf("only one of line_start_pattern or line_end_pattern can be set")
 }
 
 // LineStartSplitFunc creates a bufio.SplitFunc that splits an incoming stream into
@@ -61,8 +66,7 @@ func LineStartSplitFunc(re *regexp.Regexp, omitPattern bool, flushAtEOF bool) bu
 			}
 			return 0, nil, nil // read more data and try again.
 		}
-		firstMatchStart := firstLoc[0]
-		firstMatchEnd := firstLoc[1]
+		firstMatchStart, firstMatchEnd := firstLoc[0], firstLoc[1]
 
 		if firstMatchStart != 0 {
 			// the beginning of the file does not match the start pattern, so return a token up to the first match so we don't lose data
diff --git a/pkg/stanza/split/split_test.go b/pkg/stanza/split/split_test.go
index 9db4b7dbb39e..27495a95e69c 100644
--- a/pkg/stanza/split/split_test.go
+++ b/pkg/stanza/split/split_test.go
@@ -41,6 +41,16 @@ func TestConfigFunc(t *testing.T) {
 		assert.Equal(t, raw[:maxLogSize], token)
 	})
 
+	t.Run("NopEncodingError", func(t *testing.T) {
+		endCfg := Config{LineEndPattern: "\n"}
+		_, err := endCfg.Func(encoding.Nop, false, 0)
+		require.Equal(t, err, fmt.Errorf("line_end_pattern should not be set when using nop encoding"))
+
+		startCfg := Config{LineStartPattern: "\n"}
+		_, err = startCfg.Func(encoding.Nop, false, 0)
+		require.Equal(t, err, fmt.Errorf("line_start_pattern should not be set when using nop encoding"))
+	})
+
 	t.Run("Newline", func(t *testing.T) {
 		cfg := Config{}
 		f, err := cfg.Func(unicode.UTF8, false, maxLogSize)
@@ -778,16 +788,6 @@ func TestNoSplitFunc(t *testing.T) {
 	}
 }
 
-func TestNoopEncodingError(t *testing.T) {
-	endCfg := Config{LineEndPattern: "\n"}
-	_, err := endCfg.Func(encoding.Nop, false, 0)
-	require.Equal(t, err, fmt.Errorf("line_start_pattern or line_end_pattern should not be set when using nop encoding"))
-
-	startCfg := Config{LineStartPattern: "\n"}
-	_, err = startCfg.Func(encoding.Nop, false, 0)
-	require.Equal(t, err, fmt.Errorf("line_start_pattern or line_end_pattern should not be set when using nop encoding"))
-}
-
 func TestNewlineSplitFunc_Encodings(t *testing.T) {
 	cases := []struct {
 		name     string