Added testcase for #591

testdata/scad/bugs/issue591.scad

@@ -0,0 +1,25 @@
+// Creates the same "non-manifold" object (sharing one edge) using two techniques:
+// o linear_extrude of two 2D objects
+// o union of two linear_extrudes
+//
+// Subsequently cuts away the non-manifold part:
+// -> the first technique fails, the second one succeeds
+//
+module cutoff() {
+    difference() {
+        children();
+        translate([0,0,2.5]) cube(2, center=true);
+    }
+}
+
+cutoff() {
+    linear_extrude(height=3, scale=[0,1], convexity=2) {
+        translate([1,0,0]) square(1,true);
+        translate([-1,0,0]) square(1,true);
+    }
+}
+
+translate([0,2,0]) cutoff() {
+    linear_extrude(height=3, scale=[0,1]) translate([1,0,0]) square(1,true);
+    linear_extrude(height=3, scale=[0,1]) translate([-1,0,0]) square(1,true);
+}

tests/CMakeLists.txt

@@ -891,6 +891,7 @@ list(APPEND BUGS_FILES ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/issue495.scad
                        ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/issue578b.scad
                        ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/issue582.scad
                        ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/issue584.scad
+                       ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/issue591.scad
                        ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/issue585.scad)
 
 list(APPEND OPENCSGTEST_FILES ${BUGS_FILES})