chore: import upstream snapshot with attribution

metadata/metadata.go

@@ -0,0 +1,126 @@
+// Package metadata is a way of defining message headers
+package metadata
+
+import (
+	"context"
+	"strings"
+)
+
+type metadataKey struct{}
+
+// Metadata is our way of representing request headers internally.
+// They're used at the RPC level and translate back and forth
+// from Transport headers.
+type Metadata map[string]string
+
+func (md Metadata) Get(key string) (string, bool) {
+	// attempt to get as is
+	val, ok := md[key]
+	if ok {
+		return val, ok
+	}
+
+	// attempt to get lower case
+	val, ok = md[strings.Title(key)]
+	return val, ok
+}
+
+func (md Metadata) Set(key, val string) {
+	md[key] = val
+}
+
+func (md Metadata) Delete(key string) {
+	// delete key as-is
+	delete(md, key)
+	// delete also Title key
+	delete(md, strings.Title(key))
+}
+
+// Copy makes a copy of the metadata.
+func Copy(md Metadata) Metadata {
+	cmd := make(Metadata, len(md))
+	for k, v := range md {
+		cmd[k] = v
+	}
+	return cmd
+}
+
+// Delete key from metadata.
+func Delete(ctx context.Context, k string) context.Context {
+	return Set(ctx, k, "")
+}
+
+// Set add key with val to metadata.
+func Set(ctx context.Context, k, v string) context.Context {
+	md, ok := FromContext(ctx)
+	if !ok {
+		md = make(Metadata)
+	}
+	if v == "" {
+		delete(md, k)
+	} else {
+		md[k] = v
+	}
+	return context.WithValue(ctx, metadataKey{}, md)
+}
+
+// Get returns a single value from metadata in the context.
+func Get(ctx context.Context, key string) (string, bool) {
+	md, ok := FromContext(ctx)
+	if !ok {
+		return "", ok
+	}
+	// attempt to get as is
+	val, ok := md[key]
+	if ok {
+		return val, ok
+	}
+
+	// attempt to get lower case
+	val, ok = md[strings.Title(key)]
+
+	return val, ok
+}
+
+// FromContext returns metadata from the given context.
+func FromContext(ctx context.Context) (Metadata, bool) {
+	md, ok := ctx.Value(metadataKey{}).(Metadata)
+	if !ok {
+		return nil, ok
+	}
+
+	// capitalise all values
+	newMD := make(Metadata, len(md))
+	for k, v := range md {
+		newMD[k] = v
+	}
+
+	return newMD, ok
+}
+
+// NewContext creates a new context with the given metadata.
+func NewContext(ctx context.Context, md Metadata) context.Context {
+	return context.WithValue(ctx, metadataKey{}, md)
+}
+
+// MergeContext merges metadata to existing metadata, overwriting if specified.
+func MergeContext(ctx context.Context, patchMd Metadata, overwrite bool) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	md, _ := ctx.Value(metadataKey{}).(Metadata)
+	cmd := make(Metadata, len(md))
+	for k, v := range md {
+		cmd[k] = v
+	}
+	for k, v := range patchMd {
+		if _, ok := cmd[k]; ok && !overwrite {
+			// skip
+		} else if v != "" {
+			cmd[k] = v
+		} else {
+			delete(cmd, k)
+		}
+	}
+	return context.WithValue(ctx, metadataKey{}, cmd)
+}

metadata/metadata_test.go

@@ -0,0 +1,114 @@
+package metadata
+
+import (
+	"context"
+	"reflect"
+	"testing"
+)
+
+func TestMetadataSet(t *testing.T) {
+	ctx := Set(context.TODO(), "Key", "val")
+
+	val, ok := Get(ctx, "Key")
+	if !ok {
+		t.Fatal("key Key not found")
+	}
+	if val != "val" {
+		t.Errorf("key Key with value val != %v", val)
+	}
+}
+
+func TestMetadataDelete(t *testing.T) {
+	md := Metadata{
+		"Foo": "bar",
+		"Baz": "empty",
+	}
+
+	ctx := NewContext(context.TODO(), md)
+	ctx = Delete(ctx, "Baz")
+
+	emd, ok := FromContext(ctx)
+	if !ok {
+		t.Fatal("key Key not found")
+	}
+
+	_, ok = emd["Baz"]
+	if ok {
+		t.Fatal("key Baz not deleted")
+	}
+}
+
+func TestMetadataCopy(t *testing.T) {
+	md := Metadata{
+		"Foo": "bar",
+		"bar": "baz",
+	}
+
+	cp := Copy(md)
+
+	for k, v := range md {
+		if cv := cp[k]; cv != v {
+			t.Fatalf("Got %s:%s for %s:%s", k, cv, k, v)
+		}
+	}
+}
+
+func TestMetadataContext(t *testing.T) {
+	md := Metadata{
+		"Foo": "bar",
+	}
+
+	ctx := NewContext(context.TODO(), md)
+
+	emd, ok := FromContext(ctx)
+	if !ok {
+		t.Errorf("Unexpected error retrieving metadata, got %t", ok)
+	}
+
+	if emd["Foo"] != md["Foo"] {
+		t.Errorf("Expected key: %s val: %s, got key: %s val: %s", "Foo", md["Foo"], "Foo", emd["Foo"])
+	}
+
+	if i := len(emd); i != 1 {
+		t.Errorf("Expected metadata length 1 got %d", i)
+	}
+}
+
+func TestMergeContext(t *testing.T) {
+	type args struct {
+		existing  Metadata
+		append    Metadata
+		overwrite bool
+	}
+	tests := []struct {
+		name string
+		args args
+		want Metadata
+	}{
+		{
+			name: "matching key, overwrite false",
+			args: args{
+				existing:  Metadata{"Foo": "bar", "Sumo": "demo"},
+				append:    Metadata{"Sumo": "demo2"},
+				overwrite: false,
+			},
+			want: Metadata{"Foo": "bar", "Sumo": "demo"},
+		},
+		{
+			name: "matching key, overwrite true",
+			args: args{
+				existing:  Metadata{"Foo": "bar", "Sumo": "demo"},
+				append:    Metadata{"Sumo": "demo2"},
+				overwrite: true,
+			},
+			want: Metadata{"Foo": "bar", "Sumo": "demo2"},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got, _ := FromContext(MergeContext(NewContext(context.TODO(), tt.args.existing), tt.args.append, tt.args.overwrite)); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("MergeContext() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}