stacklok · JAORMX · Mar 24, 2025 · Mar 24, 2025 · Mar 24, 2025
diff --git a/cmd/actions/actions.go b/cmd/actions/actions.go
@@ -93,6 +93,11 @@ func replaceCmd(cmd *cobra.Command, args []string) error {
 		if err != nil {
 			return err
 		}
+
+		if err := cliFlags.CheckModified(res.Modified); err != nil {
+			return err
+		}
+
 		// Process the output files
 		return cliFlags.ProcessOutput(dir, res.Processed, res.Modified)
 	}

diff --git a/internal/cli/cli.go b/internal/cli/cli.go
@@ -17,6 +17,7 @@
 package cli
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -165,6 +166,21 @@ func (r *Helper) Logf(format string, args ...interface{}) {
 	}
 }
 
+// CheckModified checks if any files were modified and returns an error if there were.
+func (r *Helper) CheckModified(modified map[string]string) error {
+	if len(modified) > 0 && r.ErrOnModified {
+		if !r.Quiet {
+			for path := range modified {
+				r.Logf("Modified: %s\n", path)
+			}
+		}
+
+		return errors.New("files were modified")
+	}
+
+	return nil
+}
+
 // ProcessOutput processes the given output files.
 // If the command is quiet, the output is discarded.
 // If the command is a dry run, the output is written to the command's stdout.

diff --git a/internal/cli/cli_test.go b/internal/cli/cli_test.go
@@ -76,6 +76,102 @@ func TestNewHelper(t *testing.T) {
 	}
 }
 
+func TestCheckModified(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name         string
+		helper       *Helper
+		modified     map[string]string
+		expectOutput string
+		expectError  bool
+	}{
+		{
+			name: "NoFilesModified",
+			helper: &Helper{
+				ErrOnModified: true,
+				Quiet:         false,
+				Cmd:           &cobra.Command{},
+			},
+			modified:     map[string]string{},
+			expectOutput: "",
+			expectError:  false,
+		},
+		{
+			name: "FilesModifiedWithErrorFlag",
+			helper: &Helper{
+				ErrOnModified: true,
+				Quiet:         false,
+				Cmd:           &cobra.Command{},
+			},
+			modified: map[string]string{
+				"file1.txt": "modified content",
+				"file2.txt": "another modified content",
+			},
+			expectOutput: "Modified: file1.txt\nModified: file2.txt",
+			expectError:  true,
+		},
+		{
+			name: "FilesModifiedWithoutErrorFlag",
+			helper: &Helper{
+				ErrOnModified: false,
+				Quiet:         false,
+				Cmd:           &cobra.Command{},
+			},
+			modified: map[string]string{
+				"file1.txt": "modified content",
+			},
+			expectOutput: "",
+			expectError:  false,
+		},
+		{
+			name: "FilesModifiedWithErrorFlagAndQuiet",
+			helper: &Helper{
+				ErrOnModified: true,
+				Quiet:         true,
+				Cmd:           &cobra.Command{},
+			},
+			modified: map[string]string{
+				"file1.txt": "modified content",
+			},
+			expectOutput: "",
+			expectError:  true,
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Set up command error output
+			var output strings.Builder
+			tt.helper.Cmd.SetErr(&output)
+
+			// Call the CheckModified method
+			err := tt.helper.CheckModified(tt.modified)
+
+			// Check if error status matches expectation
+			if tt.expectError {
+				assert.Error(t, err)
+				assert.Equal(t, "files were modified", err.Error())
+			} else {
+				assert.NoError(t, err)
+			}
+
+			// Check if output contains expected strings
+			if tt.expectOutput != "" {
+				// We can't guarantee the order of map iteration, so we check that
+				// the output contains each expected line
+				for path := range tt.modified {
+					if !tt.helper.Quiet {
+						assert.Contains(t, output.String(), "Modified: "+path)
+					}
+				}
+			}
+		})
+	}
+}
+
 func TestProcessOutput(t *testing.T) {
 	t.Parallel()