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Fix SVG namespace prefixes in HTML emails with attachments #170

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Fix SVG namespace prefixes in HTML emails with attachments #170

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507aa4c
Bump Claude allowed commands
awdeorio Jan 14, 2026
fc8a36f
Add test exposing bug
awdeorio Jan 14, 2026
328998c
Use html5lib for serialization
awdeorio Jan 14, 2026
6c724e5
Merge remote-tracking branch 'origin/develop' into issue165
awdeorio Jan 16, 2026
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8 changes: 6 additions & 2 deletions mailmerge/template_message.py
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,6 @@

import re
from pathlib import Path
from xml.etree import ElementTree
import email
import email.mime
import email.mime.application
Expand Down Expand Up @@ -294,7 +293,12 @@ def _transform_attachment_references(self):
# We only need to update the message if we cleared the header,
# which only happens if we transformed an attachment reference.
if 'Content-Transfer-Encoding' not in part:
new_html = ElementTree.tostring(document).decode('utf-8')
new_html = html5lib.serialize(
document,
tree='etree',
omit_optional_tags=False,
quote_attr_values='always',
)
part.set_payload(new_html)

def _resolve_attachment_path(self, path):
Expand Down
58 changes: 58 additions & 0 deletions tests/test_template_message.py
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Original file line number Diff line number Diff line change
Expand Up @@ -865,3 +865,61 @@ def test_content_id_header_for_attachments(tmpdir):
assert filename == "attachment.txt"
assert content == b"Hello world\n"
assert re.match(r'<[\d\w]+(\.[\d\w]+)*@mailmerge\.invalid>', cid_header)


def test_svg_with_attachment(tmp_path):
"""SVG elements should not have namespace prefixes when attachments exist.

Regression test for https://github.com/awdeorio/mailmerge/issues/165
"""
# Create a dummy attachment
attachment_path = tmp_path / "image.png"
attachment_path.write_bytes(b"fake png data")

# Create template with inline SVG and an attachment referencing the image
template_path = tmp_path / "template.txt"
template_path.write_text(textwrap.dedent("""\
TO: to@test.com
FROM: from@test.com
SUBJECT: SVG Test
ATTACHMENT: image.png
Content-Type: text/html

<html>
<body>
<svg id="circle" viewBox="0 0 100 100">
<circle cx="50" cy="50" r="40" fill="green" />
</svg>
<img src="image.png" alt="test" />
</body>
</html>
"""), encoding="utf8")

# Render template
template_message = TemplateMessage(template_path)
_, _, message = template_message.render({})

# Get the HTML part
assert message.is_multipart()
html_part = None
for part in message.walk():
if part.get_content_type() == "text/html":
html_part = part
break
assert html_part is not None

# Get HTML content
html_content = html_part.get_payload(decode=True).decode("utf-8")

# Verify SVG elements do NOT have namespace prefixes
assert "ns0:svg" not in html_content, \
"SVG element should not have namespace prefix"
assert "ns0:circle" not in html_content, \
"circle element should not have namespace prefix"

# Verify SVG elements are present (without prefixes)
assert "<svg" in html_content, "SVG element should be present"
assert "<circle" in html_content, "circle element should be present"

# Verify the image src was transformed to a CID reference
assert "cid:" in html_content, "Image src should be transformed to CID"