statsig-rust unconditionally enables serde_json/preserve_order, causing workspace-wide side effects for consumers

[max-zheng]

Problem

statsig-rust (since v0.15.1) unconditionally enables serde_json's preserve_order feature:

[dependencies.serde_json]
version = "1.0.143"
features = [
    "float_roundtrip",
    "raw_value",
    "preserve_order",
]

Due to Cargo's feature unification, this changes serde_json::Value's internal Map from BTreeMap (alphabetically sorted keys) to IndexMap (insertion-order keys) for every crate in the consumer's workspace — not just statsig-rust.

Impact

Adding statsig-rust to any crate in a workspace silently changes serialization behavior for all other crates:

• JSON output key ordering changes from alphabetical to insertion order
• Test snapshots break
• Generated files (e.g. OpenAPI specs) produce unnecessary diffs
• Deterministic serialization assumptions break

These issues are extremely hard to trace back to a transitive dependency. Having this side effect can definitely make customers less likely to adopt this crate since it will have workspace-wide side effects to one of the most widely used rust crates.

Suggestion

Ideally, remove the preserve_order dependency entirely by rewriting any code that relies on insertion-order JSON keys. If that's not feasible, please make it opt-in via a feature flag instead:

[features]
preserve_order = ["serde_json/preserve_order"]

[dependencies.serde_json]
version = "1.0.143"
features = [
    "float_roundtrip",
    "raw_value",
]