Avoid building image for buf export when --exclude-imports flag i…

…s set (#3009)

This PR changes `buf export` so that when `--exclude-imports` is
passed, it does not require the input to be buildable as an image.
This allows a user to provide an input that may not be buildable, and
they can still get the source files back when `--exclude-imports` is
set, since we do not need the image to check for import files.

Fixes #3002

private/buf/cmd/buf/command/export/export.go

@@ -150,15 +150,6 @@ func run(
  return err
  }
  moduleReadBucket := bufmodule.ModuleSetToModuleReadBucketWithOnlyProtoFiles(workspace)
- image, err := controller.GetImageForWorkspace(
- ctx,
- workspace,
- bufctl.WithImageExcludeSourceInfo(true),
- bufctl.WithImageExcludeImports(flags.ExcludeImports),
- )
- if err != nil {
- return err
- }
 
  if err := os.MkdirAll(flags.Output, 0755); err != nil {
  return err
@@ -174,6 +165,40 @@ func run(
  if err != nil {
  return err
  }
+
+ // In the case where we are excluding imports, we are allowing users to specify an input
+ // that may not have resolved imports (https://github.com/bufbuild/buf/issues/3002).
+ // Thus we do not need to build the image, and instead we can return the non-import files
+ // from the workspace.
+ if flags.ExcludeImports {
+ if err := moduleReadBucket.WalkFileInfos(
+ ctx,
+ func(fileInfo bufmodule.FileInfo) error {
+ moduleFile, err := moduleReadBucket.GetFile(ctx, fileInfo.Path())
+ if err != nil {
+ return syserror.Wrap(err)
+ }
+ if err := storage.CopyReadObject(ctx, readWriteBucket, moduleFile); err != nil {
+ return multierr.Append(err, moduleFile.Close())
+ }
+ return moduleFile.Close()
+ },
+ bufmodule.WalkFileInfosWithOnlyTargetFiles(),
+ ); err != nil {
+ return err
+ }
+ return nil
+ }
+
+ image, err := controller.GetImageForWorkspace(
+ ctx,
+ workspace,
+ bufctl.WithImageExcludeSourceInfo(true),
+ bufctl.WithImageExcludeImports(flags.ExcludeImports),
+ )
+ if err != nil {
+ return err
+ }
  imageFiles := image.Files()
  if len(imageFiles) == 0 {
  return errors.New("no .proto target files found")