Validate XML boundary names

[vinitkumar]

Summary by Sourcery

Validate XML names for custom roots and attribute keys to prevent malformed XML output and ensure consistent name normalization.

Bug Fixes:

• Normalize invalid custom root element names using the existing XML-name rules before emitting raw XML bytes.
• Reject invalid XML attribute names for custom attributes so malformed XML is not produced.

Documentation:

• Document expected behavior for custom root name normalization and invalid custom attribute rejection in the test behavior guide.

Tests:

• Add tests covering normalization of invalid custom root names and explicit failure on invalid custom attribute names.

[sourcery-ai]

Reviewer's Guide

Validates XML attribute and root element names to prevent malformed XML, and aligns custom root handling with existing XML name normalization, with tests and LAT docs updated accordingly.

Flow diagram for XML attribute name validation in make_attrstring

flowchart TD
  A[make_attrstring receives attr dict] --> B{attr is empty?}
  B -- yes --> C[Return empty string]
  B -- no --> D[validate_xml_attr_names]
  D --> E{Iterate keys in attr}
  E --> F[key_is_valid_xml_attr]
  F --> G{minidom parseString succeeds?}
  G -- no --> H[Raise ValueError Invalid XML attribute name]
  G -- yes --> I[All keys valid]
  I --> J[Build attribute string and return]

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Flow diagram for custom_root XML name normalization in dicttoxml

flowchart TD
  A[dicttoxml called with custom_root] --> B{root is True?}
  B -- no --> C[Call convert with parent empty]
  B -- yes --> D[Append XML declaration]
  D --> E[make_valid_xml_name with custom_root and empty attrs]
  E --> F[Receive normalized custom_root and root_attr]
  F --> G[Call convert with parent normalized custom_root]
  G --> H["Build root start tag with make_attrstring(root_attr) and namespace_str"]
  H --> I[Append closing tag using normalized custom_root]

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File-Level Changes

Change	Details	Files
Validate XML attribute names before emitting them and reuse existing XML-name normalization for custom root names.	Call a new XML attribute-name validation helper at the start of attribute string rendering so invalid attribute keys raise instead of producing malformed XML. Introduce key_is_valid_xml_attr using defusedxml.minidom plus an LRU cache to cheaply test whether attribute names are syntactically valid in XML. Add validate_xml_attr_names to iterate over @attrs keys and reject any invalid XML attribute names with a ValueError. Normalize custom_root via make_valid_xml_name so it follows the same XML name rules as object keys before building the root tag, and plumb any returned attributes through make_attrstring in the root element output.	json2xml/dicttoxml.py
Extend tests and LAT documentation to pin new behavior for custom root normalization and invalid attributes.	Add a test ensuring invalid custom_root values are normalized using existing XML-name rules before raw XML bytes are produced, preventing malformed root tags. Add a test asserting that invalid @attrs keys now raise ValueError instead of emitting malformed XML attributes. Update LAT test documentation to describe custom root name normalization and explicit rejection of invalid custom attributes.	tests/test_dict2xml.py lat.md/tests.md

Possibly linked issues

• #0: PR implements part of the issue: normalizing invalid custom root names and rejecting invalid @attrs XML attribute names.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (f9c2bcf) to head (e50a5eb).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #306   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          552       570   +18     
=========================================
+ Hits           552       570   +18     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="tests/test_dict2xml.py" line_range="511-519" />
<code_context>
+            b"<custom_root><key>value</key></custom_root>"
+        )
+
+    # @lat: [[tests#Conversion behavior#Invalid custom attributes are rejected]]
+    def test_dicttoxml_rejects_invalid_custom_attribute_names(self) -> None:
+        """Invalid custom attribute names should fail before dicttoxml returns malformed XML bytes."""
+        with pytest.raises(ValueError, match="Invalid XML attribute name"):
+            dicttoxml.dicttoxml(
+                {"key": {"@attrs": {"bad attr": "value"}, "@val": "payload"}},
+                root=False,
+                attr_type=False,
+            )
+
</code_context>
<issue_to_address>
**suggestion (testing):** Consider broadening attribute-name tests to cover multiple invalid and valid edge-case names

The new `test_dicttoxml_rejects_invalid_custom_attribute_names` currently exercises only one invalid attribute (`"bad attr"`). To strengthen coverage of `key_is_valid_xml_attr` / `validate_xml_attr_names`, please parameterize this test (or add more) to include:

- Several invalid names (e.g. `""`, `"1foo"`, `"foo>bar"`, something with a newline or quote).
- A few borderline valid names (e.g. `"a_b"`, `"a-b"`, `"xmlAttr"`) to confirm the validator isn’t over-restrictive.

This will better cover edge-case attribute names and the XML-based validation behavior.

```suggestion
    # @lat: [[tests#Conversion behavior#Invalid custom attributes are rejected]]
    @pytest.mark.parametrize(
        "attr_name",
        [
            "bad attr",   # space
            "",           # empty
            "1foo",       # starts with digit
            "foo>bar",    # invalid character
            "foo\nbar",   # newline
            'foo"bar',    # quote
        ],
    )
    def test_dicttoxml_rejects_invalid_custom_attribute_names(self, attr_name: str) -> None:
        """Invalid custom attribute names should fail before dicttoxml returns malformed XML bytes."""
        with pytest.raises(ValueError, match="Invalid XML attribute name"):
            dicttoxml.dicttoxml(
                {"key": {"@attrs": {attr_name: "value"}, "@val": "payload"}},
                root=False,
                attr_type=False,
            )

    @pytest.mark.parametrize(
        "attr_name",
        [
            "a_b",      # underscore
            "a-b",      # hyphen
            "xmlAttr",  # mixed case, xml-prefixed but still syntactically valid
        ],
    )
    def test_dicttoxml_accepts_valid_custom_attribute_names(self, attr_name: str) -> None:
        """Borderline-but-valid attribute names should be accepted by the XML attribute validator."""
        result = dicttoxml.dicttoxml(
            {"key": {"@attrs": {attr_name: "value"}, "@val": "payload"}},
            root=False,
            attr_type=False,
        )
        # We don't assert exact XML shape here; reaching this point means no ValueError was raised.
        assert isinstance(result, bytes)
```
</issue_to_address>

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