`serde_json::Value` broken with latest release

[oscartbeaumont]

It's Type impl is recursive. This will be fixed by #454

Repro:

use std::collections::HashMap;

use serde::Serialize;
use specta::{Type, TypeCollection};
use specta_typescript::Typescript;

#[derive(Serialize, Type)]
#[serde(rename_all = "camelCase")]
pub(crate) struct Policy {
    #[serde(default, skip_serializing_if = "Option::is_none")]
    configurations: Option<HashMap<String, serde_json::Value>>, // TODO: Fix Specta on value type
}

fn main() {
    println!(
        "{}",
        Typescript::default()
            .export(&TypeCollection::default().register::<Policy>())
            .unwrap()
    );
}

for personal context: Found on Mattrax Policy.configurations and skipped for now.

We need better testing for custom impls!!!!

[oscartbeaumont]

AI Review:

Nice repro — I dug into it and found the likely root cause.
serde_json::Value’s Type impl in specta/src/type/legacy_impls.rs:31 is structurally recursive (Array(Vec), Object(Map<String, Value>)) but currently builds via direct Value::definition(...) calls, which leads to infinite recursion during type construction and stack overflow.
Plan

• Patch the Type for serde_json::Value impl in specta/src/type/legacy_impls.rs to use NamedDataType::init_with_sentinel(...) (same recursion guard strategy the derive macro uses), and return a DataType::Reference(...) instead of directly nesting Value::definition.
• Keep the enum shape the same (Null | Bool | Number | String | Array | Object), but inside Array/Object, recursive uses of Value will resolve to a named reference rather than re-entering definition expansion.
• Add a regression test in the dedicated tests crate (tests/tests/typescript.rs) that reproduces your exact case (Option<HashMap<String, serde_json::Value>>) and verifies Typescript::export(...) succeeds (no stack overflow).
• Include an issue-link comment above that regression test (per repo convention), then run targeted validation:
  • cargo test -p specta-tests <new_test_name>
  • cargo run -p specta-typescript --example mttx_bug
• If we want to harden further, apply the same sentinel pattern to other recursive legacy external Value impls (notably serde_yaml::Value and toml::Value) in the same file.
  One decision before I implement: should I keep this fix minimal (serde_json only, fastest) or do a broader hardening pass (serde_json + serde_yaml + toml) in one change?
  My recommendation: broader hardening pass, since the recursion pattern is the same.