From 6c8f5bcaf130edcd364dc45fa44502e24b18c5fa Mon Sep 17 00:00:00 2001
From: Martin Polden <mpolden@mpolden.no>
Date: Thu, 16 Mar 2023 08:46:01 +0100
Subject: Report byte offset on parse error

---
 client/go/internal/vespa/feed/document.go      |  8 ++++++++
 client/go/internal/vespa/feed/document_test.go | 21 +++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/client/go/internal/vespa/feed/document.go b/client/go/internal/vespa/feed/document.go
index eccbb80b7c2..609e3f6c5aa 100644
--- a/client/go/internal/vespa/feed/document.go
+++ b/client/go/internal/vespa/feed/document.go
@@ -95,6 +95,14 @@ func (d *Decoder) readCloseToken() error {
 }
 
 func (d *Decoder) Decode() (Document, error) {
+	doc, err := d.decode()
+	if err != nil && err != io.EOF {
+		return Document{}, fmt.Errorf("invalid json at byte offset %d: %w", d.dec.InputOffset(), err)
+	}
+	return doc, err
+}
+
+func (d *Decoder) decode() (Document, error) {
 	if err := d.guessMode(); err != nil {
 		return Document{}, err
 	}
diff --git a/client/go/internal/vespa/feed/document_test.go b/client/go/internal/vespa/feed/document_test.go
index 6c8f92bdaa6..452c184a05a 100644
--- a/client/go/internal/vespa/feed/document_test.go
+++ b/client/go/internal/vespa/feed/document_test.go
@@ -132,4 +132,25 @@ func testDocumentDecoder(t *testing.T, jsonLike string) {
 func TestDocumentDecoder(t *testing.T) {
 	testDocumentDecoder(t, feedInput(false))
 	testDocumentDecoder(t, feedInput(true))
+
+	jsonLike := `
+{
+  "put": "id:ns:type::doc1",
+  "fields": {"foo": "123"}
+}
+{
+  "put": "id:ns:type::doc1",
+  "fields": {"foo": "invalid
+}
+`
+	r := NewDecoder(strings.NewReader(jsonLike))
+	_, err := r.Decode() // first object is valid
+	if err != nil {
+		t.Errorf("unexpected error: %s", err)
+	}
+	_, err = r.Decode()
+	wantErr := "invalid json at byte offset 60: invalid character '\\n' in string literal"
+	if err.Error() != wantErr {
+		t.Errorf("want error %q, got %q", wantErr, err.Error())
+	}
 }
-- 
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