fs: implement --metadata-mapper to transform metatadata with a user supplied program

backend/drive/metadata.go

@@ -596,7 +596,7 @@ func (f *Fs) updateMetadata(ctx context.Context, updateInfo *drive.File, meta fs
 
 // Fetch metadata and update updateInfo if --metadata is in use
 func (f *Fs) fetchAndUpdateMetadata(ctx context.Context, src fs.ObjectInfo, options []fs.OpenOption, updateInfo *drive.File, update bool) (callback updateMetadataFn, err error) {
-	meta, err := fs.GetMetadataOptions(ctx, src, options)
+	meta, err := fs.GetMetadataOptions(ctx, f, src, options)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read metadata from source object: %w", err)
 	}

backend/internetarchive/internetarchive.go

@@ -802,7 +802,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		headers["x-archive-size-hint"] = fmt.Sprintf("%d", size)
 	}
 	var mdata fs.Metadata
-	mdata, err = fs.GetMetadataOptions(ctx, src, options)
+	mdata, err = fs.GetMetadataOptions(ctx, o.fs, src, options)
 	if err == nil && mdata != nil {
 		for mk, mv := range mdata {
 			mk = strings.ToLower(mk)

backend/jottacloud/jottacloud.go

@@ -1944,7 +1944,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 		in = wrap(in)
 	}
 	// Fetch metadata if --metadata is in use
-	meta, err := fs.GetMetadataOptions(ctx, src, options)
+	meta, err := fs.GetMetadataOptions(ctx, o.fs, src, options)
 	if err != nil {
 		return fmt.Errorf("failed to read metadata from source object: %w", err)
 	}

backend/local/local.go

@@ -1298,7 +1298,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	}
 
 	// Fetch and set metadata if --metadata is in use
-	meta, err := fs.GetMetadataOptions(ctx, src, options)
+	meta, err := fs.GetMetadataOptions(ctx, o.fs, src, options)
 	if err != nil {
 		return fmt.Errorf("failed to read metadata from source object: %w", err)
 	}

backend/oracleobjectstorage/multipart.go

@@ -295,7 +295,7 @@ func (o *Object) prepareUpload(ctx context.Context, src fs.ObjectInfo, options [
 	// Set the mtime in the metadata
 	modTime := src.ModTime(ctx)
 	// Fetch metadata if --metadata is in use
-	meta, err := fs.GetMetadataOptions(ctx, src, options)
+	meta, err := fs.GetMetadataOptions(ctx, o.fs, src, options)
 	if err != nil {
 		return ui, fmt.Errorf("failed to read metadata from source object: %w", err)
 	}

backend/s3/s3.go

@@ -6008,7 +6008,7 @@ func (o *Object) prepareUpload(ctx context.Context, src fs.ObjectInfo, options [
 	}
 
 	// Fetch metadata if --metadata is in use
-	meta, err := fs.GetMetadataOptions(ctx, src, options)
+	meta, err := fs.GetMetadataOptions(ctx, o.fs, src, options)
 	if err != nil {
 		return ui, fmt.Errorf("failed to read metadata from source object: %w", err)
 	}

bin/test_metadata_mapper.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+"""
+A demo metadata mapper
+"""
+
+import sys
+import json
+
+def main():
+    i = json.load(sys.stdin)
+    # Add tag to description
+    metadata = i["Metadata"]
+    if "description" in metadata:
+        metadata["description"] += " [migrated from domain1]"
+    else:
+        metadata["description"] = "[migrated from domain1]"
+    # Modify owner
+    if "owner" in metadata:
+        metadata["owner"] = metadata["owner"].replace("domain1.com", "domain2.com")
+    o = { "Metadata": metadata }
+    json.dump(o, sys.stdout, indent="\t")
+
+if __name__ == "__main__":
+    main()

docs/content/docs.md

@@ -475,6 +475,10 @@ Note that arbitrary metadata may be added to objects using the
 `--metadata-set key=value` flag when the object is first uploaded.
 This flag can be repeated as many times as necessary.
 
+The [--metadata-mapper](#metadata-mapper) flag can be used to pass the
+name of a program in which can transform metadata when it is being
+copied from source to destination.
+
 ### Types of metadata
 
 Metadata is divided into two type. System metadata and User metadata.
@@ -1504,12 +1508,123 @@ from reaching the limit. Only applicable for `--max-transfer`
 
 Setting this flag enables rclone to copy the metadata from the source
 to the destination. For local backends this is ownership, permissions,
-xattr etc. See the [#metadata](metadata section) for more info.
+xattr etc. See the [metadata section](#metadata) for more info.
+
+### --metadata-mapper SpaceSepList {#metadata-mapper}
+
+If you supply the parameter `--metadata-mapper /path/to/program` then
+rclone will use that program to map metadata from source object to
+destination object.
+
+The argument to this flag should be a command with an optional space separated
+list of arguments. If one of the arguments has a space in then enclose
+it in `"`, if you want a literal `"` in an argument then enclose the
+argument in `"` and double the `"`. See [CSV encoding](https://godoc.org/encoding/csv)
+for more info.
+
+    --metadata-mapper "python bin/test_metadata_mapper.py"
+    --metadata-mapper 'python bin/test_metadata_mapper.py "argument with a space"'
+    --metadata-mapper 'python bin/test_metadata_mapper.py "argument with ""two"" quotes"'
+
+This uses a simple JSON based protocol with input on STDIN and output
+on STDOUT. This will be called for every file and directory copied and
+may be called concurrently.
+
+The program's job is to take a metadata blob on the input and turn it
+into a metadata blob on the output suitable for the destination
+backend.
+
+Input to the program (via STDIN) might look like this. This provides
+some context for the `Metadata` which may be important.
+
+- `SrcFs` is the config string for the remote that the object is currently on.
+- `SrcFsType` is the name of the source backend.
+- `DstFs` is the config string for the remote that the object is being copied to
+- `DstFsType` is the name of the destination backend.
+- `Remote` is the path of the file relative to the root.
+- `Size`, `MimeType`, `ModTime` are attributes of the file.
+- `IsDir` is `true` if this is a directory (not yet implemented).
+- `ID` is the source `ID` of the file if known.
+- `Metadata` is the backend specific metadata as described in the backend docs.
+
+```json
+{
+    "SrcFs": "gdrive:",
+    "SrcFsType": "drive",
+    "DstFs": "newdrive:user",
+    "DstFsType": "onedrive",
+    "Remote": "test.txt",
+    "Size": 6,
+    "MimeType": "text/plain; charset=utf-8",
+    "ModTime": "2022-10-11T17:53:10.286745272+01:00",
+    "IsDir": false,
+    "ID": "xyz",
+    "Metadata": {
+        "btime": "2022-10-11T16:53:11Z",
+        "content-type": "text/plain; charset=utf-8",
+        "mtime": "2022-10-11T17:53:10.286745272+01:00",
+        "owner": "user1@domain1.com",
+        "permissions": "...",
+        "description": "my nice file",
+        "starred": "false"
+    }
+}
+```
+
+The program should then modify the input as desired and send it to
+STDOUT. The returned `Metadata` field will be used in its entirety for
+the destination object. Any other fields will be ignored. Note in this
+example we translate user names and permissions and add something to
+the description:
+
+```json
+{
+    "Metadata": {
+        "btime": "2022-10-11T16:53:11Z",
+        "content-type": "text/plain; charset=utf-8",
+        "mtime": "2022-10-11T17:53:10.286745272+01:00",
+        "owner": "user1@domain2.com",
+        "permissions": "...",
+        "description": "my nice file [migrated from domain1]",
+        "starred": "false"
+    }
+}
+```
+
+Metadata can be removed here too.
+
+An example python program might look something like this to implement
+the above transformations.
+
+```python
+import sys, json
+
+i = json.load(sys.stdin)
+metadata = i["Metadata"]
+# Add tag to description
+if "description" in metadata:
+    metadata["description"] += " [migrated from domain1]"
+else:
+    metadata["description"] = "[migrated from domain1]"
+# Modify owner
+if "owner" in metadata:
+    metadata["owner"] = metadata["owner"].replace("domain1.com", "domain2.com")
+o = { "Metadata": metadata }
+json.dump(o, sys.stdout, indent="\t")
+```
+
+You can find this example (slightly expanded) in the rclone source code at
+[bin/test_metadata_mapper.py](https://github.com/rclone/rclone/blob/master/test_metadata_mapper.py).
+
+If you want to see the input to the metadata mapper and the output
+returned from it in the log you can use `-vv --dump mapper`.
+
+See the [metadata section](#metadata) for more info.
 
 ### --metadata-set key=value
 
 Add metadata `key` = `value` when uploading. This can be repeated as
-many times as required. See the [#metadata](metadata section) for more
+many times as required. See the [metadata section](#metadata) for more
 info.
 
 ### --modify-window=TIME ###
@@ -1752,9 +1867,9 @@ for more info.
 
 Eg
 
-    --password-command echo hello
+    --password-command "echo hello"
-    --password-command echo "hello with space"
+    --password-command 'echo "hello with space"'
-    --password-command echo "hello with ""quotes"" and space"
+    --password-command 'echo "hello with ""quotes"" and space"'
 
 See the [Configuration Encryption](#configuration-encryption) for more info.
 
@@ -2503,6 +2618,12 @@ This dumps a list of the open files at the end of the command.  It
 uses the `lsof` command to do that so you'll need that installed to
 use it.
 
+#### --dump mapper ####
+
+This shows the JSON blobs being sent to the program supplied with
+`--metadata-mapper` and received from it. It can be useful for
+debugging the metadata mapper interface.
+
 ### --memprofile=FILE ###
 
 Write memory profile to file. This can be analysed with `go tool pprof`.

fs/config.go

@@ -149,6 +149,7 @@ type ConfigInfo struct {
 	DefaultTime                Time // time that directories with no time should display
 	Inplace                    bool // Download directly to destination file instead of atomic download to temp/rename
 	PartialSuffix              string
+	MetadataMapper             SpaceSepList
 }
 
 // NewConfig creates a new config with everything set to the default

fs/config/configflags/configflags.go

@@ -150,6 +150,7 @@ func AddFlags(ci *fs.ConfigInfo, flagSet *pflag.FlagSet) {
 	flags.FVarP(flagSet, &ci.DefaultTime, "default-time", "", "Time to show if modtime is unknown for files and directories", "Config,Listing")
 	flags.BoolVarP(flagSet, &ci.Inplace, "inplace", "", ci.Inplace, "Download directly to destination file instead of atomic download to temp/rename", "Copy")
 	flags.StringVarP(flagSet, &partialSuffix, "partial-suffix", "", ci.PartialSuffix, "Add partial-suffix to temporary file name when --inplace is not used", "Copy")
+	flags.FVarP(flagSet, &ci.MetadataMapper, "metadata-mapper", "", "Program to run to transforming metadata before upload", "Metadata")
 }
 
 // ParseHeaders converts the strings passed in via the header flags into HTTPOptions

fs/dump.go

@@ -13,6 +13,7 @@ const (
 	DumpFilters
 	DumpGoRoutines
 	DumpOpenFiles
+	DumpMapper
 )
 
 type dumpChoices struct{}
@@ -27,6 +28,7 @@ func (dumpChoices) Choices() []BitsChoicesInfo {
 		{uint64(DumpFilters), "filters"},
 		{uint64(DumpGoRoutines), "goroutines"},
 		{uint64(DumpOpenFiles), "openfiles"},
+		{uint64(DumpMapper), "mapper"},
 	}
 }
 

fs/metadata.go

@@ -1,6 +1,14 @@
 package fs
 
-import "context"
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
 
 // Metadata represents Object metadata in a standardised form
 //
@@ -66,12 +74,85 @@ func GetMetadata(ctx context.Context, o ObjectInfo) (metadata Metadata, err erro
 	return do.Metadata(ctx)
 }
 
+// mapItem descripts the item to be mapped
+type mapItem struct {
+	SrcFs     string
+	SrcFsType string
+	DstFs     string
+	DstFsType string
+	Remote    string
+	Size      int64
+	MimeType  string `json:",omitempty"`
+	ModTime   time.Time
+	IsDir     bool
+	ID        string   `json:",omitempty"`
+	Metadata  Metadata `json:",omitempty"`
+}
+
+// This runs an external program on the metadata which can be used to
+// map it from one form to another.
+func metadataMapper(ctx context.Context, cmdLine SpaceSepList, dstFs Fs, o ObjectInfo, metadata Metadata) (newMetadata Metadata, err error) {
+	ci := GetConfig(ctx)
+	cmd := exec.Command(cmdLine[0], cmdLine[1:]...)
+	in := mapItem{
+		DstFs:     ConfigString(dstFs),
+		DstFsType: Type(dstFs),
+		Remote:    o.Remote(),
+		Size:      o.Size(),
+		MimeType:  MimeType(ctx, o),
+		ModTime:   o.ModTime(ctx),
+		IsDir:     false,
+		Metadata:  metadata,
+	}
+	fInfo := o.Fs()
+	if f, ok := fInfo.(Fs); ok {
+		in.SrcFs = ConfigString(f)
+		in.SrcFsType = Type(f)
+	} else {
+		in.SrcFs = fInfo.Name() + ":" + fInfo.Root()
+		in.SrcFsType = "unknown"
+	}
+	if do, ok := o.(IDer); ok {
+		in.ID = do.ID()
+	}
+	inBytes, err := json.MarshalIndent(in, "", "\t")
+	if err != nil {
+		return nil, fmt.Errorf("metadata mapper: failed to marshal input: %w", err)
+	}
+	if ci.Dump.IsSet(DumpMapper) {
+		Debugf(nil, "Metadata mapper sent: \n%s\n", string(inBytes))
+	}
+	var stdout, stderr bytes.Buffer
+	cmd.Stdin = bytes.NewBuffer(inBytes)
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	start := time.Now()
+	err = cmd.Run()
+	Debugf(o, "Calling metadata mapper %v", cmdLine)
+	duration := time.Since(start)
+	if err != nil {
+		return nil, fmt.Errorf("metadata mapper: failed on %v: %q: %w", cmdLine, strings.TrimSpace(stderr.String()), err)
+	}
+	if ci.Dump.IsSet(DumpMapper) {
+		Debugf(nil, "Metadata mapper received: \n%s\n", stdout.String())
+	}
+	var out mapItem
+	err = json.Unmarshal(stdout.Bytes(), &out)
+	if err != nil {
+		return nil, fmt.Errorf("metadata mapper: failed to read output: %q: %w", stdout.String(), err)
+	}
+	Debugf(o, "Metadata mapper returned in %v", duration)
+	return out.Metadata, nil
+}
+
 // GetMetadataOptions from an ObjectInfo and merge it with any in options
 //
-// If --metadata isn't in use it will return nil
+// If --metadata isn't in use it will return nil.
 //
-// If the object has no metadata then metadata will be nil
+// If the object has no metadata then metadata will be nil.
-func GetMetadataOptions(ctx context.Context, o ObjectInfo, options []OpenOption) (metadata Metadata, err error) {
+//
+// This should be passed the destination Fs for the metadata mapper
+func GetMetadataOptions(ctx context.Context, dstFs Fs, o ObjectInfo, options []OpenOption) (metadata Metadata, err error) {
 	ci := GetConfig(ctx)
 	if !ci.Metadata {
 		return nil, nil
@@ -81,5 +162,11 @@ func GetMetadataOptions(ctx context.Context, o ObjectInfo, options []OpenOption)
 		return nil, err
 	}
 	metadata.MergeOptions(options)
+	if len(ci.MetadataMapper) != 0 {
+		metadata, err = metadataMapper(ctx, ci.MetadataMapper, dstFs, o, metadata)
+		if err != nil {
+			return nil, err
+		}
+	}
 	return metadata, nil
 }

fs/metadata_mapper_code.go

@@ -0,0 +1,75 @@
+//go:build ignore
+// +build ignore
+
+// A simple metadata mapper for testing purposes
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+)
+
+func check[T comparable](in map[string]any, key string, want T) {
+	value, ok := in[key]
+	if !ok {
+		fmt.Fprintf(os.Stderr, "%s key not found\n", key)
+		os.Exit(1)
+	}
+	if value.(T) != want {
+		fmt.Fprintf(os.Stderr, "%s wrong - expecting %s but got %s\n", key, want, value)
+		os.Exit(1)
+	}
+}
+
+func main() {
+	// Read the input
+	var in map[string]any
+	err := json.NewDecoder(os.Stdin).Decode(&in)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Check the input
+	metadata, ok := in["Metadata"]
+	if !ok {
+		fmt.Fprintf(os.Stderr, "Metadata key not found\n")
+		os.Exit(1)
+	}
+	check(in, "Size", 5.0)
+	check(in, "SrcFs", "memory:")
+	check(in, "SrcFsType", "object.memoryFs")
+	check(in, "DstFs", "dstFs:dstFsRoot")
+	check(in, "DstFsType", "mockfs")
+	check(in, "Remote", "file.txt")
+	check(in, "MimeType", "text/plain; charset=utf-8")
+	check(in, "ModTime", "2001-02-03T04:05:06.000000007Z")
+	check(in, "IsDir", false)
+	//check(in, "ID", "Potato")
+
+	// Map the metadata
+	metadataOut := map[string]string{}
+	var out = map[string]any{
+		"Metadata": metadataOut,
+	}
+	for k, v := range metadata.(map[string]any) {
+		switch k {
+		case "error":
+			fmt.Fprintf(os.Stderr, "Error: %s\n", v)
+			os.Exit(1)
+		case "key1":
+			v = "two " + v.(string)
+		case "key3":
+			continue
+		}
+		metadataOut[k] = v.(string)
+	}
+	metadataOut["key0"] = "cabbage"
+
+	// Write the output
+	json.NewEncoder(os.Stdout).Encode(&out)
+	if err != nil {
+		log.Fatal(err)
+	}
+}

fs/metadata_test.go

@@ -1,14 +1,20 @@
-package fs
+package fs_test
 
 import (
+	"context"
 	"fmt"
 	"testing"
+	"time"
 
+	"github.com/rclone/rclone/fs"
+	"github.com/rclone/rclone/fs/object"
+	"github.com/rclone/rclone/fstest/mockfs"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestMetadataSet(t *testing.T) {
-	var m Metadata
+	var m fs.Metadata
 	assert.Nil(t, m)
 	m.Set("key", "value")
 	assert.NotNil(t, m)
@@ -19,34 +25,34 @@ func TestMetadataSet(t *testing.T) {
 
 func TestMetadataMerge(t *testing.T) {
 	for _, test := range []struct {
-		in    Metadata
+		in    fs.Metadata
-		merge Metadata
+		merge fs.Metadata
-		want  Metadata
+		want  fs.Metadata
 	}{
 		{
-			in:    Metadata{},
+			in:    fs.Metadata{},
-			merge: Metadata{},
+			merge: fs.Metadata{},
-			want:  Metadata{},
+			want:  fs.Metadata{},
 		}, {
 			in:    nil,
 			merge: nil,
 			want:  nil,
 		}, {
 			in:    nil,
-			merge: Metadata{},
+			merge: fs.Metadata{},
 			want:  nil,
 		}, {
 			in:    nil,
-			merge: Metadata{"a": "1", "b": "2"},
+			merge: fs.Metadata{"a": "1", "b": "2"},
-			want:  Metadata{"a": "1", "b": "2"},
+			want:  fs.Metadata{"a": "1", "b": "2"},
 		}, {
-			in:    Metadata{"a": "1", "b": "2"},
+			in:    fs.Metadata{"a": "1", "b": "2"},
 			merge: nil,
-			want:  Metadata{"a": "1", "b": "2"},
+			want:  fs.Metadata{"a": "1", "b": "2"},
 		}, {
-			in:    Metadata{"a": "1", "b": "2"},
+			in:    fs.Metadata{"a": "1", "b": "2"},
-			merge: Metadata{"b": "B", "c": "3"},
+			merge: fs.Metadata{"b": "B", "c": "3"},
-			want:  Metadata{"a": "1", "b": "B", "c": "3"},
+			want:  fs.Metadata{"a": "1", "b": "B", "c": "3"},
 		},
 	} {
 		what := fmt.Sprintf("in=%v, merge=%v", test.in, test.merge)
@@ -57,36 +63,36 @@ func TestMetadataMerge(t *testing.T) {
 
 func TestMetadataMergeOptions(t *testing.T) {
 	for _, test := range []struct {
-		in   Metadata
+		in   fs.Metadata
-		opts []OpenOption
+		opts []fs.OpenOption
-		want Metadata
+		want fs.Metadata
 	}{
 		{
-			opts: []OpenOption{},
+			opts: []fs.OpenOption{},
 			want: nil,
 		}, {
-			opts: []OpenOption{&HTTPOption{}},
+			opts: []fs.OpenOption{&fs.HTTPOption{}},
 			want: nil,
 		}, {
-			opts: []OpenOption{MetadataOption{"a": "1", "b": "2"}},
+			opts: []fs.OpenOption{fs.MetadataOption{"a": "1", "b": "2"}},
-			want: Metadata{"a": "1", "b": "2"},
+			want: fs.Metadata{"a": "1", "b": "2"},
 		}, {
-			opts: []OpenOption{
+			opts: []fs.OpenOption{
-				&HTTPOption{},
+				&fs.HTTPOption{},
-				MetadataOption{"a": "1", "b": "2"},
+				fs.MetadataOption{"a": "1", "b": "2"},
-				MetadataOption{"b": "B", "c": "3"},
+				fs.MetadataOption{"b": "B", "c": "3"},
-				&HTTPOption{},
+				&fs.HTTPOption{},
 			},
-			want: Metadata{"a": "1", "b": "B", "c": "3"},
+			want: fs.Metadata{"a": "1", "b": "B", "c": "3"},
 		}, {
-			in: Metadata{"a": "first", "z": "OK"},
+			in: fs.Metadata{"a": "first", "z": "OK"},
-			opts: []OpenOption{
+			opts: []fs.OpenOption{
-				&HTTPOption{},
+				&fs.HTTPOption{},
-				MetadataOption{"a": "1", "b": "2"},
+				fs.MetadataOption{"a": "1", "b": "2"},
-				MetadataOption{"b": "B", "c": "3"},
+				fs.MetadataOption{"b": "B", "c": "3"},
-				&HTTPOption{},
+				&fs.HTTPOption{},
 			},
-			want: Metadata{"a": "1", "b": "B", "c": "3", "z": "OK"},
+			want: fs.Metadata{"a": "1", "b": "B", "c": "3", "z": "OK"},
 		},
 	} {
 		what := fmt.Sprintf("in=%v, opts=%v", test.in, test.opts)
@@ -94,3 +100,58 @@ func TestMetadataMergeOptions(t *testing.T) {
 		assert.Equal(t, test.want, test.in, what)
 	}
 }
+
+func TestMetadataMapper(t *testing.T) {
+	ctx := context.Background()
+	ctx, ci := fs.AddConfig(ctx)
+	ci.Metadata = true
+	require.NoError(t, ci.MetadataMapper.Set("go run metadata_mapper_code.go"))
+	now := time.Date(2001, 2, 3, 4, 5, 6, 7, time.UTC)
+	f, err := mockfs.NewFs(ctx, "dstFs", "dstFsRoot", nil)
+	require.NoError(t, err)
+
+	t.Run("Normal", func(t *testing.T) {
+		o := object.NewMemoryObject("file.txt", now, []byte("hello")).WithMetadata(fs.Metadata{
+			"key1": "potato",
+			"key2": "sausage",
+			"key3": "gravy",
+		})
+		metadata, err := fs.GetMetadataOptions(ctx, f, o, nil)
+		require.NoError(t, err)
+		assert.Equal(t, fs.Metadata{
+			"key0": "cabbage",
+			"key1": "two potato",
+			"key2": "sausage",
+		}, metadata)
+	})
+
+	t.Run("Error", func(t *testing.T) {
+		o := object.NewMemoryObject("file.txt", now, []byte("hello")).WithMetadata(fs.Metadata{
+			"error": "Red Alert",
+		})
+		metadata, err := fs.GetMetadataOptions(ctx, f, o, nil)
+		require.Error(t, err)
+		assert.ErrorContains(t, err, "Red Alert")
+		require.Nil(t, metadata)
+	})
+
+	t.Run("Merge", func(t *testing.T) {
+		o := object.NewMemoryObject("file.txt", now, []byte("hello")).WithMetadata(fs.Metadata{
+			"key1": "potato",
+			"key2": "sausage",
+			"key3": "gravy",
+		})
+		metadata, err := fs.GetMetadataOptions(ctx, f, o, []fs.OpenOption{fs.MetadataOption(fs.Metadata{
+			"option": "optionValue",
+			"key1":   "new potato",
+			"key2":   "salami",
+		})})
+		require.NoError(t, err)
+		assert.Equal(t, fs.Metadata{
+			"key0":   "cabbage",
+			"key1":   "two new potato",
+			"key2":   "salami",
+			"option": "optionValue",
+		}, metadata)
+	})
+}