From a82365ec8cc09149e71e739335135d3748299df9 Mon Sep 17 00:00:00 2001
From: Jan Petykiewicz <jan@mpxd.net>
Date: Wed, 1 Apr 2026 20:57:35 -0700
Subject: [PATCH] [svg] fix duplicate svg ids

---
 masque/file/svg.py      | 22 +++++++++++++++++++---
 masque/test/test_svg.py | 28 ++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/masque/file/svg.py b/masque/file/svg.py
index f235b50..621bcdb 100644
--- a/masque/file/svg.py
+++ b/masque/file/svg.py
@@ -30,6 +30,21 @@ def _ref_to_svg_transform(ref) -> str:
     return f'matrix({a:g} {b:g} {c:g} {d:g} {e:g} {f:g})'
 
 
+def _make_svg_ids(names: Mapping[str, Pattern]) -> dict[str, str]:
+    svg_ids: dict[str, str] = {}
+    seen_ids: set[str] = set()
+    for name in names:
+        base_id = mangle_name(name)
+        svg_id = base_id
+        suffix = 1
+        while svg_id in seen_ids:
+            suffix += 1
+            svg_id = f'{base_id}_{suffix}'
+        seen_ids.add(svg_id)
+        svg_ids[name] = svg_id
+    return svg_ids
+
+
 def writefile(
         library: Mapping[str, Pattern],
         top: str,
@@ -81,10 +96,11 @@ def writefile(
     # Create file
     svg = svgwrite.Drawing(filename, profile='full', viewBox=viewbox_string,
                            debug=(not custom_attributes))
+    svg_ids = _make_svg_ids(library)
 
     # Now create a group for each pattern and add in any Boundary and Use elements
     for name, pat in library.items():
-        svg_group = svg.g(id=mangle_name(name), fill='blue', stroke='red')
+        svg_group = svg.g(id=svg_ids[name], fill='blue', stroke='red')
 
         for layer, shapes in pat.shapes.items():
             for shape in shapes:
@@ -123,11 +139,11 @@ def writefile(
                 continue
             for ref in refs:
                 transform = _ref_to_svg_transform(ref)
-                use = svg.use(href='#' + mangle_name(target), transform=transform)
+                use = svg.use(href='#' + svg_ids[target], transform=transform)
                 svg_group.add(use)
 
         svg.defs.add(svg_group)
-    svg.add(svg.use(href='#' + mangle_name(top)))
+    svg.add(svg.use(href='#' + svg_ids[top]))
     svg.save()
 
 
diff --git a/masque/test/test_svg.py b/masque/test/test_svg.py
index a3261b6..b637853 100644
--- a/masque/test/test_svg.py
+++ b/masque/test/test_svg.py
@@ -68,3 +68,31 @@ def test_svg_ref_mirroring_changes_affine_transform(tmp_path: Path) -> None:
 
     assert_allclose(plain_transform, (0, 2, -2, 0, 3, 4), atol=1e-10)
     assert_allclose(mirrored_transform, (0, 2, 2, 0, 3, 4), atol=1e-10)
+
+
+def test_svg_uses_unique_ids_for_colliding_mangled_names(tmp_path: Path) -> None:
+    lib = Library()
+    first = Pattern()
+    first.polygon("1", vertices=[[0, 0], [1, 0], [0, 1]])
+    lib["a b"] = first
+
+    second = Pattern()
+    second.polygon("1", vertices=[[0, 0], [2, 0], [0, 2]])
+    lib["a-b"] = second
+
+    top = Pattern()
+    top.ref("a b")
+    top.ref("a-b", offset=(5, 0))
+    lib["top"] = top
+
+    svg_path = tmp_path / "colliding_ids.svg"
+    svg.writefile(lib, "top", str(svg_path))
+
+    root = ET.fromstring(svg_path.read_text())
+    ids = [group.attrib["id"] for group in root.iter(f"{SVG_NS}g")]
+    hrefs = [use.attrib[XLINK_HREF] for use in root.iter(f"{SVG_NS}use")]
+
+    assert ids.count("a_b") == 1
+    assert len(set(ids)) == len(ids)
+    assert "#a_b" in hrefs
+    assert "#a_b_2" in hrefs