fix(json): preserve falsy root values in serialized content

[Shubham Padkonde (Shubham-Padkonde)]

Overview

Root JSON values false, 0, 0.0, "" and [] currently serialize as {}, including through RequestInformation.set_content_from_scalar. Explicit root null also needs to be distinguished from an unset writer. Track root presence separately from the payload, preserve it for composed objects, use it for mixed-root/property validation, and reset it after serialization.

Related Issue

Fixes #742

Testing Instructions

From packages/serialization/json, install requirements-dev.txt and run pytest.

• 148 package tests pass on Windows/Python 3.12.
• 28 added cases cover root round trips, writer reuse, mixed-root/property rejection, actual RequestInformation content, and composed-object null serialization. The original falsy-root regressions produced 16 failures before the initial fix; both added root-null cases failed before the review follow-up.
• Mypy (6 source files), YAPF and isort checks pass. The repository's pylint command exits successfully with 10.00/10, while reporting the existing unrecognized suggestion-mode configuration option.

Notes

AI-assisted implementation and testing. The full multi-package and Python-version CI matrix was not run locally. This starts from main and is independent of #741, which fixes empty property names.

[Copilot]

Copilot review overview

🟡 Changes recommended

Root null values remain indistinguishable from an unset writer state.

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Review effort: Lite
Findings: 1

Open (1)

• Track root null presence separately from unset writer state · New

What changed in this PR

Fixes JSON serialization of falsy root values and adds regression coverage.

Changes:

• Preserves falsy root values during serialization.
• Adds tests for root values, mixed roots, writer reuse, and request content.

File	Summary
packages/​serialization/​json/​tests/​unit/​test_root_values.py	Adds regression tests for root values and request content.
packages/​serialization/​json/​kiota_serialization_json/​json_serialization_writer.py	Updates root-value serialization and validation logic.

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[Shubham Padkonde (Shubham-Padkonde)]

Addressed the root-null finding by tracking root presence separately from its payload, including composed-object serialization, and clearing that state after serialization. The new root-null cases failed on the previous implementation; all 148 JSON tests now pass, along with mypy, YAPF, isort and the repository's pylint command (exit 0; existing suggestion-mode configuration diagnostic remains).

The last two lines in the round-trip test verify writer reuse: after serializing a root value, writing a named property must succeed without stale root state causing an invalid mixed-root error. I added a comment explaining that purpose. Agent-assisted update.

[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved issues were identified, and all reviewed changes have regression coverage.

Review effort: Lite
Findings: None

Resolved since last review (1)

• Track root null presence separately from unset writer state

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud