build: bring in strings.Cut to build on go1.17

go.mod

@@ -1,6 +1,6 @@
 module github.com/howeyc/ledger
 
-go 1.18
+go 1.17
 
 require (
 	github.com/alfredxing/calc v0.0.0-20180827002445-77daf576f976

ledgerReader.go

@@ -57,7 +57,7 @@ func includeFile(filename string, buf *bytes.Buffer) error {
 	for s.Scan() {
 		line := s.Text()
 
-		if prefix, incname, found := strings.Cut(line, " "); found && prefix == "include" {
+		if prefix, incname, found := stringsCut(line, " "); found && prefix == "include" {
 			// Resolve filepaths
 			includedPath := filepath.Join(filename, "..", incname)
 			includedPaths, err := filepath.Glob(includedPath)

parse.go

@@ -91,7 +91,7 @@ func parseLedger(ledgerReader io.Reader, callback func(t *Transaction, err error
 			continue
 		}
 
-		before, after, split := strings.Cut(trimmedLine, " ")
+		before, after, split := stringsCut(trimmedLine, " ")
 		if !split {
 			if callback(nil, fmt.Errorf("%s:%d: Unable to parse transaction: %w", lp.filename, lp.lineCount,
 				fmt.Errorf("Unable to parse payee line: %s", line))) {

parseFuzz_test.go

@@ -0,0 +1,30 @@
+//go:build go1.18
+
+package ledger
+
+import (
+	"bytes"
+	"math/big"
+	"testing"
+)
+
+func FuzzParseLedger(f *testing.F) {
+	for _, tc := range testCases {
+		if tc.err == nil {
+			f.Add(tc.data)
+		}
+	}
+	f.Fuzz(func(t *testing.T, s string) {
+		b := bytes.NewBufferString(s)
+		trans, _ := ParseLedger(b)
+		overall := new(big.Rat)
+		for _, t := range trans {
+			for _, p := range t.AccountChanges {
+				overall.Add(overall, p.Balance)
+			}
+		}
+		if overall.Cmp(new(big.Rat)) != 0 {
+			t.Error("Bad balance")
+		}
+	})
+}

parse_test.go

@@ -449,27 +449,6 @@ func TestParseLedger(t *testing.T) {
 	}
 }
 
-func FuzzParseLedger(f *testing.F) {
-	for _, tc := range testCases {
-		if tc.err == nil {
-			f.Add(tc.data)
-		}
-	}
-	f.Fuzz(func(t *testing.T, s string) {
-		b := bytes.NewBufferString(s)
-		trans, _ := ParseLedger(b)
-		overall := new(big.Rat)
-		for _, t := range trans {
-			for _, p := range t.AccountChanges {
-				overall.Add(overall, p.Balance)
-			}
-		}
-		if overall.Cmp(new(big.Rat)) != 0 {
-			t.Error("Bad balance")
-		}
-	})
-}
-
 func BenchmarkParseLedger(b *testing.B) {
 	tc := testCase{
 		"benchmark",

scut.go

@@ -0,0 +1,14 @@
+package ledger
+
+import "strings"
+
+// Cut slices s around the first instance of sep,
+// returning the text before and after sep.
+// The found result reports whether sep appears in s.
+// If sep does not appear in s, cut returns s, "", false.
+func stringsCut(s, sep string) (before, after string, found bool) {
+	if i := strings.Index(s, sep); i >= 0 {
+		return s[:i], s[i+len(sep):], true
+	}
+	return s, "", false
+}