ContractFunctionResult._to_proto() silently sends signer_nonce=0 when it should be omitted

[utkarsh232005]

Description

When serializing a ContractFunctionResult object using _to_proto(), if the signer_nonce attribute is None (which is its default state), the SDK incorrectly wraps it in a protobuf Int64Value(value=None).

In modern Python protobuf libraries, this silently creates an Int64Value object with the default value of 0 instead of omitting the field entirely.

This breaks the distinction between signer_nonce=0 and "signer_nonce is not present", causing the SDK to silently send a nonce of 0 when no nonce was intended.

---

Root Cause

In src/hiero_sdk_python/contract/contract_function_result.py around line 510, the _to_proto() method unconditionally wraps self.signer_nonce in a Google Protobuf Int64Value:

def _to_proto(self) -> contract_types_pb2.ContractFunctionResult:
    return contract_types_pb2.ContractFunctionResult(
        ...
        signer_nonce=Int64Value(value=self.signer_nonce),  # <-- Bug occurs here
        ...
    )

Because self.signer_nonce defaults to None at initialization, Int64Value(value=None) is called. Instead of throwing an error, modern protobuf libraries silently construct an Int64Value populated with the default value (0).

The existing unit tests do not catch this because they explicitly set signer_nonce=10 in the test fixtures.

---

Fix

Update the _to_proto() method to conditionally wrap signer_nonce, similar to how other optional attributes are handled and matching the logic used in _from_proto().

File:

src/hiero_sdk_python/contract/contract_function_result.py

Before:

signer_nonce=Int64Value(value=self.signer_nonce),

After:

signer_nonce=Int64Value(value=self.signer_nonce)
if self.signer_nonce is not None else None,

---

Steps to Reproduce

Run the following command:

PYTHONPATH=src python3 -c "from hiero_sdk_python.contract.contract_function_result import ContractFunctionResult; print(ContractFunctionResult()._to_proto())"

---

Additional Context

refrence:- hashgraph/hedera-sdk-reference#149

Hedera Network

No response

---

Version

• SDK Version: main branch
• Python Version: 3.10+
• Protobuf Version: 4.21.12+

---

Operating System

macOS

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[github-actions]

@coderabbitai plan

[manishdait]

@utkarsh232005, Thanks for creating the issue

[github-actions]

👋 Hi @manishdait! If you'd like to work on this issue, please comment /assign to get assigned.

[coderabbitai]

Coding Plan

Summary

• Apply a simple conditional guard to the signer_nonce serialization in _to_proto(), following the existing pattern for other optional wrapper-type fields like evm_address
• Add targeted unit test coverage for the signer_nonce=None case that was previously untested
• The fix is minimal and surgical, directly addressing the root cause without broader refactoring

Implementation Steps

Fix signer_nonce Serialization and Add Test Coverage

This phase addresses the core bug by adding a None-guard to the _to_proto() method and ensures the fix is verified with proper test coverage for the previously untested edge case.

Task 1: Add None-guard to signer_nonce in _to_proto()

Update the serialization logic to conditionally wrap signer_nonce only when it has a value, matching the pattern used for other optional wrapper types.

• Modify src/hiero_sdk_python/contract/contract_function_result.py in the _to_proto() method (around line 510)
• Change the unconditional Int64Value(value=self.signer_nonce) to use a conditional expression
• Apply the pattern: Int64Value(value=self.signer_nonce) if self.signer_nonce is not None else None
• This mirrors the existing evm_address handling which uses BytesValue(...) if self.evm_address else None

Task 2: Add Unit Test for signer_nonce=None Case

Add test coverage to verify that _to_proto() correctly omits signer_nonce when it is None, preventing regression.

• Add a new test function in tests/unit/contract_function_result_test.py
• Create a minimal ContractFunctionResult instance with signer_nonce left as default (None)
• Call _to_proto() on this instance and assert that proto.signer_nonce is falsy (not set) or that proto.HasField('signer_nonce') returns False
• Optionally add a complementary assertion confirming that when signer_nonce=0 is explicitly set, it is correctly serialized as Int64Value(value=0) to preserve the semantic distinction

🤖 Prompt for AI agents

This phase fixes a serialization bug in `ContractFunctionResult._to_proto()` and
adds corresponding unit test coverage.

**Task 1: Fix `_to_proto()` in
`src/hiero_sdk_python/contract/contract_function_result.py`**
- Locate the `_to_proto()` method (around line 510)
- Find the line that unconditionally sets `signer_nonce` using
`Int64Value(value=self.signer_nonce)`
- Replace it with a conditional expression: `Int64Value(value=self.signer_nonce)
if self.signer_nonce is not None else None`
- This follows the same pattern already used for `evm_address`: `BytesValue(...)
if self.evm_address else None`

**Task 2: Add unit tests in `tests/unit/contract_function_result_test.py`**
- Add a new test function that creates a minimal `ContractFunctionResult`
instance with `signer_nonce` left as its default (`None`)
- Call `_to_proto()` on the instance and assert that `proto.signer_nonce` is
falsy (not set), or assert `proto.HasField('signer_nonce')` returns `False`
- Optionally, add a complementary assertion: when `signer_nonce=0` is explicitly
set, the result should serialize as `Int64Value(value=0)`, preserving the
semantic distinction between "no nonce" and "nonce equals zero"

Research

The ContractFunctionResult class is a dataclass in src/hiero_sdk_python/contract/contract_function_result.py with 12 optional fields, including signer_nonce: int | None = None. The _to_proto() method serializes the object to a protobuf message, while _from_proto() deserializes from protobuf. The _from_proto() method correctly handles the optional signer_nonce with a conditional guard, but _to_proto() lacks this guard. The existing test suite in tests/unit/contract_function_result_test.py only exercises _to_proto() with signer_nonce=10, leaving the None case untested.

---

🚀 Next Steps

🤖 All AI agent prompts combined

This phase fixes a serialization bug in `ContractFunctionResult._to_proto()` and
adds corresponding unit test coverage.

**Task 1: Fix `_to_proto()` in
`src/hiero_sdk_python/contract/contract_function_result.py`**
- Locate the `_to_proto()` method (around line 510)
- Find the line that unconditionally sets `signer_nonce` using
`Int64Value(value=self.signer_nonce)`
- Replace it with a conditional expression: `Int64Value(value=self.signer_nonce)
if self.signer_nonce is not None else None`
- This follows the same pattern already used for `evm_address`: `BytesValue(...)
if self.evm_address else None`

**Task 2: Add unit tests in `tests/unit/contract_function_result_test.py`**
- Add a new test function that creates a minimal `ContractFunctionResult`
instance with `signer_nonce` left as its default (`None`)
- Call `_to_proto()` on the instance and assert that `proto.signer_nonce` is
falsy (not set), or assert `proto.HasField('signer_nonce')` returns `False`
- Optionally, add a complementary assertion: when `signer_nonce=0` is explicitly
set, the result should serialize as `Int64Value(value=0)`, preserving the
semantic distinction between "no nonce" and "nonce equals zero"

💡 Iterate on the plan with: @coderabbitai <feedback>

Example Feedback
- `@coderabbitai` You can skip phase 3. Add a simple unit test case for phase 2.
- `@coderabbitai` For design choice 1 go ahead with option 3 and replan.

---

💬 Have feedback or questions? Drop into our discord!

[utkarsh232005]

/assign

[github-actions]

👋 Hi @utkarsh232005! Thanks for your interest in contributing 💡

Before taking on a beginner issue, we ask contributors to complete at least one Good First Issue to get familiar with the workflow.

👉 Find a Good First Issue here

Please try a GFI first, then come back — we’ll be happy to assign this! 😊

[utkarsh232005]

@manishdait can you assign me on this