[Storage] az storage blob allow empty blob with data

[Pan-Qi]

Related command

az storage blob upload

Description

Fix issue: #31852

Fixes az storage blob upload --data '' so an explicitly empty data value is treated as provided input and can be used to upload an empty blob.

The upload validator now checks whether --data is omitted by comparing against None, instead of relying on truthiness. This preserves the existing validation for missing input and mutually exclusive --file / --data arguments.

Added unit test coverage for empty --data, non-empty --data, file upload input, conflicting --file and --data, and missing upload input.

Testing Guide

History Notes

[Component Name 1] BREAKING CHANGE: az command a: Make some customer-facing breaking change
[Component Name 2] az command b: Add some customer-facing feature

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[yonzhan]

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[Copilot]

Pull request overview

This pull request fixes az storage blob upload --data '' so an explicitly empty --data value is treated as provided input (rather than being rejected as “missing”), enabling uploads of empty blobs via --data.

Changes:

• Updated validate_upload_blob to detect “data was provided” via namespace.data is not None instead of truthiness checks.
• Added unit tests covering empty/non-empty --data, --file, mutual exclusivity errors, and missing input errors.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/azure-cli/azure/cli/command_modules/storage/_validators.py	Adjusts upload input validation to allow empty-string --data while preserving mutual exclusivity and required-input checks.
src/azure-cli/azure/cli/command_modules/storage/tests/latest/test_storage_validators.py	Adds direct unit coverage for validate_upload_blob across expected valid/invalid input combinations.

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