proof: return correct error

If the meta data isn't JSON when we expect it to be, we return the
correct error.

Author: guggero

proof/meta.go

@@ -182,13 +182,13 @@ func DecodeMetaJSON(jBytes []byte) (map[string]interface{}, error) {
 	// These bytes must match our metadata size constraints.
 	err := IsValidMetaSize(jBytes, MetaDataMaxSizeBytes)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("%w: %s", ErrInvalidJSON, err.Error())
 	}
 
 	// Unmarshal checks internally if the JSON is valid.
 	err = json.Unmarshal(jBytes, &jMeta)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("%w: %s", ErrInvalidJSON, err.Error())
 	}
 
 	return jMeta, nil

proof/meta_test.go

@@ -1,11 +1,25 @@
 package proof
 
 import (
+	"bytes"
+	"encoding/hex"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 )
 
+var (
+	// proofInvalidJsonHexFileName is the name of the file that contains the
+	// hex proof data for a proof where the meta type is declared as JSON
+	// but the data is not valid JSON.
+	proofInvalidJsonHexFileName = filepath.Join(
+		testDataFileName, "proof-invalid-json-meta-reveal.hex",
+	)
+)
+
 func TestValidateMetaReveal(t *testing.T) {
 	t.Parallel()
 
@@ -78,3 +92,26 @@ func TestValidateMetaReveal(t *testing.T) {
 		})
 	}
 }
+
+// TestProofInvalidJsonMetaReveal tests that a proof with a meta reveal that
+// is declared as JSON but is not valid JSON will return the correct error when
+// trying to decode the decimal display.
+func TestProofInvalidJsonMetaReveal(t *testing.T) {
+	proofHex, err := os.ReadFile(proofInvalidJsonHexFileName)
+	require.NoError(t, err)
+
+	proofBytes, err := hex.DecodeString(
+		strings.Trim(string(proofHex), "\n"),
+	)
+	require.NoError(t, err)
+
+	p := &Proof{}
+	err = p.Decode(bytes.NewReader(proofBytes))
+	require.NoError(t, err)
+
+	require.NotNil(t, p.MetaReveal)
+
+	_, decDisplay, err := p.MetaReveal.GetDecDisplay()
+	require.ErrorIs(t, err, ErrInvalidJSON)
+	require.Zero(t, decDisplay)
+}