feat: do another round of memory optimisations

[vinitkumar]

Summary by Sourcery

Stream XML serialization through a lightweight UTF-8 writer to reduce intermediate string allocations while preserving the public dicttoxml API.

New Features:

• Introduce an internal _XMLWriter helper to accumulate UTF-8-encoded XML output as bytes.

Enhancements:

• Add streaming variants of dict and list conversion helpers that append XML directly to the shared writer instead of building joined subtree strings.
• Update dicttoxml XPath and normal code paths to use the streaming writer, reducing peak memory usage for large payloads.
• Clarify architecture documentation to describe the new streaming writer and its role in normal and XPath serialization.

[sourcery-ai]

Reviewer's Guide

Refactors the JSON-to-XML serializer to stream UTF-8 bytes via a new _XMLWriter and append-style helpers instead of building large intermediate strings, applying this both to normal dicttoxml output and XPath 3.1 json-to-xml mode, and updates the architecture docs accordingly.

File-Level Changes

Change	Details	Files
Introduce a streaming UTF-8 writer and append-style conversion helpers so dicttoxml and XPath modes emit bytes incrementally instead of assembling large intermediate strings.	Add _XMLWriter helper that buffers UTF-8-encoded bytes and exposes write()/to_bytes(). Add _append_xpath31 that recursively serializes XPath 3.1 json-to-xml structures directly into an _XMLWriter, including optional namespace emission for top-level map/array or wrapped scalars. Introduce _append_convert and its helpers (_append_convert_dict, _append_convert_list, _append_dict2xml_str, _append_list2xml_str, _append_rawitem) that mirror existing convert*/dict2xml_str/list2xml_str logic but write directly to an _XMLWriter instead of returning joined strings. Refactor dicttoxml(xpath_format=True) to build the XPath document by streaming into _XMLWriter based on get_xpath31_tag_name(obj) instead of using convert_to_xpath31 and string replace tricks for xmlns injection. Refactor dicttoxml normal path to construct the XML declaration and optional root wrapper by streaming into _XMLWriter, using _append_convert for the body, and returning output.to_bytes() for both rooted and rootless output. Update architecture documentation to describe dicttoxml’s new streaming behavior via _XMLWriter and clarify that public helpers still return strings while library/CLI paths now write bytes incrementally.	json2xml/dicttoxml.py lat.md/architecture.md

---

Tips and commands

Interacting with Sourcery

• Trigger a new review: Comment @sourcery-ai review on the pull request.
• Continue discussions: Reply directly to Sourcery's review comments.
• Generate a GitHub issue from a review comment: Ask Sourcery to create an
  issue from a review comment by replying to it. You can also reply to a
  review comment with @sourcery-ai issue to create an issue from it.
• Generate a pull request title: Write @sourcery-ai anywhere in the pull
  request title to generate a title at any time. You can also comment
  @sourcery-ai title on the pull request to (re-)generate the title at any time.
• Generate a pull request summary: Write @sourcery-ai summary anywhere in
  the pull request body to generate a PR summary at any time exactly where you
  want it. You can also comment @sourcery-ai summary on the pull request to
  (re-)generate the summary at any time.
• Generate reviewer's guide: Comment @sourcery-ai guide on the pull
  request to (re-)generate the reviewer's guide at any time.
• Resolve all Sourcery comments: Comment @sourcery-ai resolve on the
  pull request to resolve all Sourcery comments. Useful if you've already
  addressed all the comments and don't want to see them anymore.
• Dismiss all Sourcery reviews: Comment @sourcery-ai dismiss on the pull
  request to dismiss all existing Sourcery reviews. Especially useful if you
  want to start fresh with a new review - don't forget to comment
  @sourcery-ai review to trigger a new review!

Customizing Your Experience

Access your dashboard to:

• Enable or disable review features such as the Sourcery-generated pull request
  summary, the reviewer's guide, and others.
• Change the review language.
• Add, remove or edit custom review instructions.
• Adjust other review settings.

Getting Help

• Contact our support team for questions or feedback.
• Visit our documentation for detailed guides and information.
• Keep in touch with the Sourcery team by following us on X/Twitter, LinkedIn or GitHub.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (389eb56) to head (b06ca10).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #316   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         6           
  Lines          569       609   +40     
=========================================
+ Hits           569       609   +40     

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

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

[sourcery-ai]

Hey - I've left some high level feedback:

• The new streaming helpers (e.g. _append_convert, _append_convert_dict, _append_convert_list, _append_xpath31) duplicate a lot of the branching and type-specific logic from the existing convert_* functions; consider factoring shared cases into common helpers so the string-returning and streaming paths stay behaviorally aligned over time.
• Several _append_* helpers mutate the attr dict in place when attr_type is true (e.g. attr["type"] = ... in _append_dict2xml_str and _append_list2xml_str); if the same attr instance can be reused across calls, it may be safer to copy or construct a fresh dict before mutation to avoid subtle attribute leakage between elements.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The new streaming helpers (e.g. `_append_convert`, `_append_convert_dict`, `_append_convert_list`, `_append_xpath31`) duplicate a lot of the branching and type-specific logic from the existing `convert_*` functions; consider factoring shared cases into common helpers so the string-returning and streaming paths stay behaviorally aligned over time.
- Several `_append_*` helpers mutate the `attr` dict in place when `attr_type` is true (e.g. `attr["type"] = ...` in `_append_dict2xml_str` and `_append_list2xml_str`); if the same `attr` instance can be reused across calls, it may be safer to copy or construct a fresh dict before mutation to avoid subtle attribute leakage between elements.

---

Sourcery is free for open source - if you like our reviews please consider sharing them ✨

• X
• Mastodon
• LinkedIn
• Facebook

_{Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.}