Code review changes.

x/mongo/driver/compression.go

@@ -26,7 +26,10 @@ type CompressionOpts struct {
  UncompressedSize int32
 }
 
-func zstdNewWriter(lvl zstd.EncoderLevel) *zstd.Encoder {
+// mustZstdNewWriter creates a zstd.Encoder with the given level and a nil
+// destination writer. It panics on any errors and should only be used at
+// package initialization time.
+func mustZstdNewWriter(lvl zstd.EncoderLevel) *zstd.Encoder {
  enc, err := zstd.NewWriter(nil, zstd.WithEncoderLevel(lvl))
  if err != nil {
  panic(err)
@@ -36,18 +39,18 @@ func zstdNewWriter(lvl zstd.EncoderLevel) *zstd.Encoder {
 
 var zstdEncoders = [zstd.SpeedBestCompression + 1]*zstd.Encoder{
  0: nil, // zstd.speedNotSet
- zstd.SpeedFastest: zstdNewWriter(zstd.SpeedFastest),
- zstd.SpeedDefault: zstdNewWriter(zstd.SpeedDefault),
- zstd.SpeedBetterCompression: zstdNewWriter(zstd.SpeedBetterCompression),
- zstd.SpeedBestCompression: zstdNewWriter(zstd.SpeedBestCompression),
+ zstd.SpeedFastest: mustZstdNewWriter(zstd.SpeedFastest),
+ zstd.SpeedDefault: mustZstdNewWriter(zstd.SpeedDefault),
+ zstd.SpeedBetterCompression: mustZstdNewWriter(zstd.SpeedBetterCompression),
+ zstd.SpeedBestCompression: mustZstdNewWriter(zstd.SpeedBestCompression),
 }
 
 func getZstdEncoder(level zstd.EncoderLevel) (*zstd.Encoder, error) {
  if zstd.SpeedFastest <= level && level <= zstd.SpeedBestCompression {
  return zstdEncoders[level], nil
  }
- // The level is invalid so call zstd.NewWriter for the error.
- return zstd.NewWriter(nil, zstd.WithEncoderLevel(level))
+ // The level is outside the expected range, return an error.
+ return nil, fmt.Errorf("invalid zstd compression level: %d", level)
 }
 
 // zlibEncodersOffset is the offset into the zlibEncoders array for a given
@@ -68,9 +71,8 @@ func getZlibEncoder(level int) (*zlibEncoder, error) {
  enc := &zlibEncoder{writer: writer, level: level}
  return enc, nil
  }
- // The level is invalid so call zlib.NewWriterLever for the error.
- _, err := zlib.NewWriterLevel(nil, level)
- return nil, err
+ // The level is outside the expected range, return an error.
+ return nil, fmt.Errorf("invalid zlib compression level: %d", level)
 }
 
 func putZlibEncoder(enc *zlibEncoder) {

x/mongo/driver/compression_test.go

@@ -47,13 +47,6 @@ func TestCompression(t *testing.T) {
 }
 
 func TestCompressionLevels(t *testing.T) {
- errEq := func(e1, e2 error) bool {
- if e1 == nil || e2 == nil {
- return (e1 == nil) == (e2 == nil)
- }
- return e1.Error() == e2.Error()
- }
-
  in := []byte("abc")
  wr := new(bytes.Buffer)
 
@@ -65,8 +58,10 @@ func TestCompressionLevels(t *testing.T) {
  opts.ZlibLevel = lvl
  _, err1 := CompressPayload(in, opts)
  _, err2 := zlib.NewWriterLevel(wr, lvl)
- if !errEq(err1, err2) {
- t.Fatalf("%d: error: %v, want: %v", lvl, err1, err2)
+ if err2 != nil {
+ assert.Error(t, err1, "expected an error for ZLib level %d", lvl)
+ } else {
+ assert.NoError(t, err1, "unexpected error for ZLib level %d", lvl)
  }
  }
  })
@@ -79,8 +74,10 @@ func TestCompressionLevels(t *testing.T) {
  opts.ZstdLevel = int(lvl)
  _, err1 := CompressPayload(in, opts)
  _, err2 := zstd.NewWriter(wr, zstd.WithEncoderLevel(zstd.EncoderLevelFromZstd(opts.ZstdLevel)))
- if !errEq(err1, err2) {
- t.Fatalf("%d: error: %v, want: %v", lvl, err1, err2)
+ if err2 != nil {
+ assert.Error(t, err1, "expected an error for Zstd level %d", lvl)
+ } else {
+ assert.NoError(t, err1, "unexpected error for Zstd level %d", lvl)
  }
  }
  })