From 5664261b832850f0f630c1a4d752364210c66988 Mon Sep 17 00:00:00 2001
From: Mike Gevaert <mgevaert@openbraininstitute.org>
Date: Wed, 27 Aug 2025 13:44:06 +0200
Subject: [PATCH] allow section type of 0 (ie: unknown/undefined) in SWC

---
 src/readers/morphologySWC.cpp |  2 +-
 tests/test_1_swc.py           | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/readers/morphologySWC.cpp b/src/readers/morphologySWC.cpp
index 80a87bbe..e778a92c 100644
--- a/src/readers/morphologySWC.cpp
+++ b/src/readers/morphologySWC.cpp
@@ -352,7 +352,7 @@ class SWCBuilder
                 throw RawDataError(err_.ERROR_SELF_PARENT(sample.id));
             }
 
-            if (sample.type >= SECTION_OUT_OF_RANGE_START || sample.type <= 0) {
+            if (sample.type >= SECTION_OUT_OF_RANGE_START || sample.type < 0) {
                 details::ErrorMessages err_(path_);
                 throw RawDataError(
                     err_.ERROR_UNSUPPORTED_SECTION_TYPE(sample.lineNumber, sample.type));
diff --git a/tests/test_1_swc.py b/tests/test_1_swc.py
index 413a6e6d..0fed3b3a 100644
--- a/tests/test_1_swc.py
+++ b/tests/test_1_swc.py
@@ -660,3 +660,13 @@ def test_WarningHandlerCollector():
     Morphology("", extension="swc", warning_handler=warnings1)
     assert len(warnings0.get_all()) == 2
     assert len(warnings1.get_all()) == 1
+
+
+def test_0_defined():
+    contents =('''
+1 1 5 2 2 3 -1
+2 0 4 2 1 1 1
+''')
+    m = Morphology(contents, "swc")
+    assert m.sections[0].type == morphio.SectionType.undefined
+