copy: do not ignore errors on Close

Signed-off-by: Giuseppe Scrivano <[email protected]>

copy/copy.go

@@ -1653,20 +1653,26 @@ func (c *copier) copyBlobFromStream(ctx context.Context, srcStream io.Reader, sr
 	return uploadedInfo, nil
 }
 
-// compressGoroutine reads all input from src and writes its compressed equivalent to dest.
-func (c *copier) compressGoroutine(dest *io.PipeWriter, src io.Reader, metadata map[string]string, compressionFormat compression.Algorithm) {
-	err := errors.New("Internal error: unexpected panic in compressGoroutine")
-	defer func() { // Note that this is not the same as {defer dest.CloseWithError(err)}; we need err to be evaluated lazily.
-		_ = dest.CloseWithError(err) // CloseWithError(nil) is equivalent to Close(), always returns nil
-	}()
-
-	compressor, err := compression.CompressStreamWithMetadata(dest, metadata, compressionFormat, c.compressionLevel)
+// doCompression reads all input from src and writes its compressed equivalent to dest.
+func doCompression(dest io.Writer, src io.Reader, metadata map[string]string, compressionFormat compression.Algorithm, compressionLevel *int) error {
+	compressor, err := compression.CompressStreamWithMetadata(dest, metadata, compressionFormat, compressionLevel)
 	if err != nil {
-		return
+		return err
 	}
-	defer compressor.Close()
 
 	buf := make([]byte, compressionBufferSize)
 
 	_, err = io.CopyBuffer(compressor, src, buf) // Sets err to nil, i.e. causes dest.Close()
+	if err != nil {
+		compressor.Close()
+		return err
+	}
+
+	return compressor.Close()
+}
+
+// compressGoroutine reads all input from src and writes its compressed equivalent to dest.
+func (c *copier) compressGoroutine(dest *io.PipeWriter, src io.Reader, metadata map[string]string, compressionFormat compression.Algorithm) {
+	err := doCompression(dest, src, metadata, compressionFormat, c.compressionLevel)
+	_ = dest.CloseWithError(err) // CloseWithError(nil) is equivalent to Close(), always returns nil
 }