Sanitize upon saving

Signed-off-by: Émile Ré <emile@getprobo.com>

pkg/prosemirror/sanitize_test.go

@@ -0,0 +1,84 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package prosemirror
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSanitizeDocumentJSON_EmptyUnchanged(t *testing.T) {
+	t.Parallel()
+
+	got, err := SanitizeDocumentJSON("")
+	require.NoError(t, err)
+	assert.Equal(t, "", got)
+
+	got, err = SanitizeDocumentJSON("   ")
+	require.NoError(t, err)
+	assert.Equal(t, "   ", got)
+}
+
+func TestSanitizeDocumentJSON_NonJSONError(t *testing.T) {
+	t.Parallel()
+
+	_, err := SanitizeDocumentJSON("plain text is not valid document JSON")
+	require.Error(t, err)
+}
+
+func TestSanitizeDocumentJSON_NonDocRootError(t *testing.T) {
+	t.Parallel()
+
+	_, err := SanitizeDocumentJSON(`{"type":"paragraph","content":[]}`)
+	require.Error(t, err)
+}
+
+func TestSanitizeDocumentJSON_LinkHref(t *testing.T) {
+	t.Parallel()
+
+	raw := `{"type":"doc","content":[{"type":"paragraph","content":[{"type":"text","marks":[{"type":"link","attrs":{"href":"javascript:alert(1)","target":"_blank"}}],"text":"click"}]}]}`
+
+	out, err := SanitizeDocumentJSON(raw)
+	require.NoError(t, err)
+
+	var doc Node
+	require.NoError(t, json.Unmarshal([]byte(out), &doc))
+	txt := doc.Content[0].Content[0]
+	require.Len(t, txt.Marks, 1)
+	attrs, err := txt.Marks[0].LinkAttrs()
+	require.NoError(t, err)
+	assert.Equal(t, "#", attrs.Href)
+	require.NotNil(t, attrs.Target)
+	assert.Equal(t, "_blank", *attrs.Target)
+}
+
+func TestSanitizeDocumentJSON_PreservesSafeHref(t *testing.T) {
+	t.Parallel()
+
+	raw := `{"type":"doc","content":[{"type":"paragraph","content":[{"type":"text","marks":[{"type":"link","attrs":{"href":"https://example.com"}}],"text":"ok"}]}]}`
+
+	out, err := SanitizeDocumentJSON(raw)
+	require.NoError(t, err)
+
+	var doc Node
+	require.NoError(t, json.Unmarshal([]byte(out), &doc))
+	txt := doc.Content[0].Content[0]
+	attrs, err := txt.Marks[0].LinkAttrs()
+	require.NoError(t, err)
+	assert.Equal(t, "https://example.com", attrs.Href)
+}