Changed UpdateFlags function to return absl::Status

[m-olko]

This PR

Update the FlagSync:UpdateFlags interface to return absl::Status and return errors on validation problems. The change also includes updating all the tests to support that.

Related Issues

Fixes #113

[gemini-code-assist]

Code Review

This pull request refactors the flag synchronization and validation logic in the flagd provider to return absl::Status instead of boolean or void, allowing for better error propagation. Callers and test suites have been updated to handle and assert on these statuses. The reviewer's feedback focuses on performance and safety improvements, suggesting the use of [[nodiscard]] to prevent ignoring returned statuses, passing JSON objects by value to enable move semantics and avoid expensive copies, and using auto for clearly deduced types.

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[gemini-code-assist]

Mark UpdateFlags with [[nodiscard]] to ensure that callers do not silently ignore validation or update errors. Additionally, pass new_json by value (nlohmann::json) instead of const nlohmann::json& to enable move semantics and avoid expensive deep copies of the flag configuration JSON.

Suggested change

	absl::Status UpdateFlags(const nlohmann::json& new_json);
	[[nodiscard]] absl::Status UpdateFlags(nlohmann::json new_json);

[gemini-code-assist]

Mark Validate with [[nodiscard]] to ensure that callers do not silently ignore validation errors.

Suggested change

	absl::Status Validate(const Json& json) const {
	[[nodiscard]] absl::Status Validate(const Json& json) const {

[gemini-code-assist]

Update the definition of UpdateFlags to accept new_json by value and mark it [[nodiscard]].

To fully leverage move semantics and avoid deep copies of the JSON structure, you should also update the body of this function (which is outside the current diff) to use std::move when extracting "flags" and "metadata":

  auto new_flags_snapshot =
      std::make_shared<const nlohmann::json>(std::move(new_json["flags"]));
  auto new_metadata_snapshot =
      std::make_shared<const nlohmann::json>(std::move(new_json["metadata"]));

Suggested change

	absl::Status FlagSync::UpdateFlags(const nlohmann::json& new_json) {
	[[nodiscard]] absl::Status FlagSync::UpdateFlags(nlohmann::json new_json) {

References

1. Avoid redundant checks for the existence of JSON fields if their presence is guaranteed by schema validation performed before the data is processed.
2. In modern C++, use 'auto' for variable declarations when the type is clearly deduced from the expression on the right-hand side.

[gemini-code-assist]

Pass raw using std::move to avoid copying the entire JSON object when calling UpdateFlags. Use auto for the status variable declaration as its type is clearly deduced from the function call.

Suggested change

	absl::Status status = UpdateFlags(raw);
	if (!status.ok()) {
	LOG(ERROR) << "Failed to update flags: " << status;
	continue;
	}
	auto status = UpdateFlags(std::move(raw));
	if (!status.ok()) {
	LOG(ERROR) << "Failed to update flags: " << status;
	continue;
	}

References

1. In modern C++, use 'auto' for variable declarations when the type is clearly deduced from the expression on the right-hand side.

[gemini-code-assist]

Update TriggerUpdate to accept new_json by value and move it to UpdateFlags to align with the new signature and avoid unnecessary copies.

Suggested change

	absl::Status TriggerUpdate(const nlohmann::json& new_json) {
	return this->UpdateFlags(new_json);
	}
	absl::Status TriggerUpdate(nlohmann::json new_json) {
	return this->UpdateFlags(std::move(new_json));
	}

[gemini-code-assist]

Update SetFlags to accept flags by value and move it to UpdateFlags to align with the new signature and avoid unnecessary copies.

Suggested change

	absl::Status SetFlags(const nlohmann::json& flags) {
	return this->UpdateFlags(flags);
	}
	absl::Status SetFlags(nlohmann::json flags) {
	return this->UpdateFlags(std::move(flags));
	}

[gemini-code-assist]

Update TriggerUpdate to accept new_json by value and move it to UpdateFlags to align with the new signature and avoid unnecessary copies.

Suggested change

	absl::Status TriggerUpdate(const nlohmann::json& new_json) {
	return this->UpdateFlags(new_json);
	}
	absl::Status TriggerUpdate(nlohmann::json new_json) {
	return this->UpdateFlags(std::move(new_json));
	}

[gemini-code-assist]

Update TriggerUpdate to accept new_json by value and move it to UpdateFlags to align with the new signature and avoid unnecessary copies.

Suggested change

	absl::Status TriggerUpdate(const nlohmann::json& new_json) {
	return this->UpdateFlags(new_json);
	}
	absl::Status TriggerUpdate(nlohmann::json new_json) {
	return this->UpdateFlags(std::move(new_json));
	}