feat: implement basic core API genesis source and target

core/genesis/source.go

@@ -0,0 +1,31 @@
+package genesis
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+
+	"cosmossdk.io/core/appmodule"
+)
+
+// SourceFromRawJSON returns a genesis source based on a raw JSON message.
+func SourceFromRawJSON(message json.RawMessage) (appmodule.GenesisSource, error) {
+	var m map[string]json.RawMessage
+	err := json.Unmarshal(message, &m)
+	if err != nil {
+		return nil, err
+	}
+	return func(field string) (io.ReadCloser, error) {
+		j, ok := m[field]
+		if !ok {
+			return nil, nil
+		}
+		return readCloserWrapper{bytes.NewReader(j)}, nil
+	}, nil
+}
+
+type readCloserWrapper struct {
+	io.Reader
+}
+
+func (r readCloserWrapper) Close() error { return nil }

core/genesis/source_test.go

@@ -0,0 +1,44 @@
+package genesis
+
+import (
+	"encoding/json"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"cosmossdk.io/core/appmodule"
+)
+
+func TestSource(t *testing.T) {
+	source, err := SourceFromRawJSON(json.RawMessage(testJSON))
+	require.NoError(t, err)
+
+	expectJSON(t, source, "foo", fooContents)
+	expectJSON(t, source, "bar", barContents)
+
+	// missing fields just return nil, nil
+	r, err := source("baz")
+	require.NoError(t, err)
+	require.Nil(t, r)
+}
+
+func expectJSON(t *testing.T, source appmodule.GenesisSource, field, contents string) {
+	r, err := source(field)
+	require.NoError(t, err)
+	bz, err := io.ReadAll(r)
+	require.NoError(t, err)
+	require.Equal(t, contents, string(bz))
+
+}
+
+const (
+	testJSON = `
+{
+	"foo":{"x":1,"y":"abc"},
+	"bar":[1,2,3,4]
+}
+`
+	fooContents = `{"x":1,"y":"abc"}`
+	barContents = `[1,2,3,4]`
+)

core/genesis/target.go

@@ -0,0 +1,44 @@
+package genesis
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+
+	"cosmossdk.io/core/appmodule"
+)
+
+// RawJSONTarget returns a struct which encapsulates a genesis target that is
+// backed by raw JSON messages. Its Target method should be used to retrieve
+// an actual genesis target function. When genesis writing is done, the JSON
+// method should be called to retrieve the raw message that has been written.
+type RawJSONTarget struct {
+	m map[string]json.RawMessage
+}
+
+// Target returns the actual genesis target function.
+func (r *RawJSONTarget) Target() appmodule.GenesisTarget {
+	return func(field string) (io.WriteCloser, error) {
+		if r.m == nil {
+			r.m = map[string]json.RawMessage{}
+		}
+
+		return &genesisWriter{Buffer: &bytes.Buffer{}, sink: r, field: field}, nil
+	}
+}
+
+// JSON returns the raw JSON message that has been written.
+func (r *RawJSONTarget) JSON() (json.RawMessage, error) {
+	return json.MarshalIndent(r.m, "", "  ")
+}
+
+type genesisWriter struct {
+	*bytes.Buffer
+	field string
+	sink  *RawJSONTarget
+}
+
+func (r genesisWriter) Close() error {
+	r.sink.m[r.field] = r.Buffer.Bytes()
+	return nil
+}

core/genesis/target_test.go

@@ -0,0 +1,33 @@
+package genesis
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestTarget(t *testing.T) {
+	target := &RawJSONTarget{}
+
+	w, err := target.Target()("foo")
+	require.NoError(t, err)
+	_, err = w.Write([]byte("1"))
+	require.NoError(t, err)
+	require.NoError(t, w.Close())
+
+	w, err = target.Target()("bar")
+	require.NoError(t, err)
+	_, err = w.Write([]byte(`"abc"`))
+	require.NoError(t, err)
+	require.NoError(t, w.Close())
+
+	bz, err := target.JSON()
+	require.NoError(t, err)
+
+	// test that it's correct by reading back with a source
+	source, err := SourceFromRawJSON(bz)
+	require.NoError(t, err)
+
+	expectJSON(t, source, "foo", "1")
+	expectJSON(t, source, "bar", `"abc"`)
+}