Merge 249efaee46 into 8e2c9b612d

README.md

@@ -433,6 +433,7 @@ Flags:
       --shell-key-separator string      separator for shell variable key paths (default "_")
   -s, --split-exp string                print each result (or doc) into a file named (exp). [exp] argument must return a string. You can use $index in the expression as the result counter. The necessary directories will be created.
       --split-exp-file string           Use a file to specify the split-exp expression.
+      --split-exp-no-overwrite          When using --split-exp, fail if a target file already exists instead of overwriting it.
       --string-interpolation            Toggles strings interpolation of \(exp) (default true)
       --tsv-auto-parse                  parse TSV YAML/JSON values (default true)
   -r, --unwrapScalar                    unwrap scalar, print the value with no quotes, colors or comments. Defaults to true for yaml (default true)

cmd/constant.go

@@ -31,6 +31,7 @@ var frontMatter = ""
 
 var splitFileExp = ""
 var splitFileExpFile = ""
+var splitFileNoOverwrite = false
 
 var completedSuccessfully = false
 

cmd/root.go

@@ -206,6 +206,7 @@ yq -P -oy sample.json
 	if err = rootCmd.MarkPersistentFlagFilename("split-exp-file"); err != nil {
 		panic(err)
 	}
+	rootCmd.PersistentFlags().BoolVarP(&splitFileNoOverwrite, "split-exp-no-overwrite", "", false, "When using --split-exp, fail if a target file already exists instead of overwriting it.")
 
 	rootCmd.PersistentFlags().StringVarP(&expressionFile, "from-file", "", "", "Load expression from specified file.")
 	if err = rootCmd.MarkPersistentFlagFilename("from-file"); err != nil {

cmd/utils.go

@@ -186,7 +186,7 @@ func configurePrinterWriter(format *yqlib.Format, out io.Writer) (yqlib.PrinterW
 		if err != nil {
 			return nil, fmt.Errorf("bad split document expression: %w", err)
 		}
-		printerWriter = yqlib.NewMultiPrinterWriter(splitExp, format)
+		printerWriter = yqlib.NewMultiPrinterWriterWithOptions(splitExp, format, splitFileNoOverwrite)
 	} else {
 		printerWriter = yqlib.NewSinglePrinterWriter(out)
 	}

pkg/yqlib/printer_writer.go

@@ -32,9 +32,17 @@ type multiPrintWriter struct {
 	nameExpression *ExpressionNode
 	extension      string
 	index          int
+	noOverwrite    bool
 }
 
 func NewMultiPrinterWriter(expression *ExpressionNode, format *Format) PrinterWriter {
+	return NewMultiPrinterWriterWithOptions(expression, format, false)
+}
+
+// NewMultiPrinterWriterWithOptions creates a multi-file printer writer.
+// When noOverwrite is true, attempting to write to a file that already
+// exists will fail with an error instead of silently overwriting it.
+func NewMultiPrinterWriterWithOptions(expression *ExpressionNode, format *Format, noOverwrite bool) PrinterWriter {
 	extension := "yml"
 
 	switch format {
@@ -49,6 +57,7 @@ func NewMultiPrinterWriter(expression *ExpressionNode, format *Format) PrinterWr
 		extension:      extension,
 		treeNavigator:  NewDataTreeNavigator(),
 		index:          0,
+		noOverwrite:    noOverwrite,
 	}
 }
 
@@ -75,10 +84,20 @@ func (sp *multiPrintWriter) GetWriter(node *CandidateNode) (*bufio.Writer, error
 	if err != nil {
 		return nil, err
 	}
-	f, err := os.Create(name)
-
-	if err != nil {
-		return nil, err
+	var f *os.File
+	if sp.noOverwrite {
+		f, err = os.OpenFile(name, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
+		if err != nil {
+			if os.IsExist(err) {
+				return nil, fmt.Errorf("refusing to overwrite existing file %q (--no-overwrite is set)", name)
+			}
+			return nil, err
+		}
+	} else {
+		f, err = os.Create(name)
+		if err != nil {
+			return nil, err
+		}
 	}
 	sp.index = sp.index + 1
 

pkg/yqlib/printer_writer_test.go

@@ -0,0 +1,96 @@
+package yqlib
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// helper to build an ExpressionNode that just yields a fixed string for the file name
+func parseFilenameExp(t *testing.T, exp string) *ExpressionNode {
+	t.Helper()
+	InitExpressionParser()
+	node, err := ExpressionParser.ParseExpression(exp)
+	if err != nil {
+		t.Fatalf("failed to parse split-exp test expression %q: %v", exp, err)
+	}
+	return node
+}
+
+func TestMultiPrinterWriterOverwriteDefault(t *testing.T) {
+	dir := t.TempDir()
+	target := filepath.Join(dir, "out.yml")
+	if err := os.WriteFile(target, []byte("pre-existing\n"), 0600); err != nil {
+		t.Fatalf("setup: %v", err)
+	}
+
+	exp := parseFilenameExp(t, `"`+target+`"`)
+	pw := NewMultiPrinterWriter(exp, YamlFormat)
+
+	node := &CandidateNode{Kind: ScalarNode, Tag: "!!str", Value: "hello"}
+	w, err := pw.GetWriter(node)
+	if err != nil {
+		t.Fatalf("default behaviour should silently overwrite, got error: %v", err)
+	}
+	if w == nil {
+		t.Fatalf("expected a writer, got nil")
+	}
+	// confirm the file was truncated/recreated by os.Create
+	info, err := os.Stat(target)
+	if err != nil {
+		t.Fatalf("stat target: %v", err)
+	}
+	if info.Size() != 0 {
+		t.Fatalf("expected file to be truncated (size 0) before writes, got %d bytes", info.Size())
+	}
+}
+
+func TestMultiPrinterWriterNoOverwriteRefusesExisting(t *testing.T) {
+	dir := t.TempDir()
+	target := filepath.Join(dir, "out.yml")
+	if err := os.WriteFile(target, []byte("pre-existing\n"), 0600); err != nil {
+		t.Fatalf("setup: %v", err)
+	}
+
+	exp := parseFilenameExp(t, `"`+target+`"`)
+	pw := NewMultiPrinterWriterWithOptions(exp, YamlFormat, true)
+
+	node := &CandidateNode{Kind: ScalarNode, Tag: "!!str", Value: "hello"}
+	_, err := pw.GetWriter(node)
+	if err == nil {
+		t.Fatalf("expected error when --no-overwrite is set and target exists, got nil")
+	}
+	if !strings.Contains(err.Error(), "refusing to overwrite") {
+		t.Fatalf("expected refusing-to-overwrite error message, got: %v", err)
+	}
+
+	// file must be untouched
+	data, err := os.ReadFile(target)
+	if err != nil {
+		t.Fatalf("read target: %v", err)
+	}
+	if string(data) != "pre-existing\n" {
+		t.Fatalf("file should be untouched, contents = %q", string(data))
+	}
+}
+
+func TestMultiPrinterWriterNoOverwriteCreatesNew(t *testing.T) {
+	dir := t.TempDir()
+	target := filepath.Join(dir, "new.yml")
+
+	exp := parseFilenameExp(t, `"`+target+`"`)
+	pw := NewMultiPrinterWriterWithOptions(exp, YamlFormat, true)
+
+	node := &CandidateNode{Kind: ScalarNode, Tag: "!!str", Value: "hello"}
+	w, err := pw.GetWriter(node)
+	if err != nil {
+		t.Fatalf("no-overwrite should still create new files, got: %v", err)
+	}
+	if w == nil {
+		t.Fatalf("expected a writer, got nil")
+	}
+	if _, err := os.Stat(target); err != nil {
+		t.Fatalf("expected new file to exist, stat err: %v", err)
+	}
+}