Added guard against negative value of max_value_len

[GauravR31]

Description

Previously, passing a negative value for max_value_len when initializing BoundedAttributes leads to Python string slicing (value[:max_value_len]) chopping characters off the end of strings instead of enforcing length limits, while logging misleading warning messages.
There was no check for a negative value, this PR adds this to the BoundedAttributes constructor.

Fixes #5646

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Before

from opentelemetry.attributes import BoundedAttributes
ba = BoundedAttributes(max_value_len=-2, immutable=False)
ba["test_key"] = "hello world"
print(dict(ba))

No ValueError is raised during __init__. The string is truncated unexpectedly from the right ({'test_key': 'hello wor'}), and an invalid warning log is emitted (String attribute value exceeds max length of -2, truncating.).

After

from opentelemetry.attributes import BoundedAttributes
ba = BoundedAttributes(max_value_len=-2, immutable=False)

    raise ValueError("max_value_len must be valid int greater or equal to 0")
ValueError: max_value_len must be valid int greater or equal to 0

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: GauravR31 / name: Gaurav Ramnani (2e2f4d2, 369c84b)

[lzchen]

@GauravR31

Please rename changelog for the PR not the ISSUE. (.changelog/5647.fixed)

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Waiting on maintainers · refreshed 2026-09-14 18:43 UTC

Merge when ready.

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[GauravR31]

@lzchen Thanks for catching that, have renamed the changelog accordingly