Preserve Prebid bidder parameter string types

[ChristianPavilonis]

Summary

• preserve nested JSON scalar types in Prebid bidder parameter override containers
• decode JSON environment overrides once without recursively coercing numeric-looking strings
• add regression coverage for TOML-to-runtime round trips and JSON environment overrides

Closes #932

Testing

• cargo fmt --all -- --check
• cargo test --package trusted-server-core --target aarch64-apple-darwin bid_param_overrides
• cargo test-axum
• cargo test-fastly

[aram356]

Summary

Correct fix for a real and broader-than-Prebid defect: IntegrationSettings::normalize() ran from finalize_deserialized(), so it applied to Settings::from_toml (adapters) and Settings::from_json_value — the runtime config-store blob path in config_payload.rs:39. Every string in every integration's config was re-parsed as JSON, turning publisherId = "12345" into 12345 before it reached the auction request. Scoping the coercion to #[cfg(test)] and calling it only from the already-#[cfg(test)] from_toml_and_env helper is the right layering, since deserialize_with = "from_value_or_str" is the sanctioned per-field string-tolerance mechanism.

I verified the removal is safe rather than assuming it: EdgeZero v0.0.4's apply_env_overlay (edgezero-core/src/app_config.rs:404-480) coerces each env string into the existing TOML value's type and explicitly rejects array/table targets. So no untyped strings reach production config, and the env-var doc examples removed from prebid.rs documented a capability production never had.

Requesting changes on two points: a missing operator-facing migration note, and four leftover tests that now assert behavior no production path has.

Blocking

🔧 wrench

• Operator-visible behavior change has no CHANGELOG entry (CHANGELOG.md): This is not only a Prebid fix — it changes type handling for all 15 integration configs. None of their enabled: bool fields use deserialize_with = "from_value_or_str" (checked every file in crates/trusted-server-core/src/integrations/), so a config carrying enabled = "true" or timeout_ms = "1000" previously loaded fine and now fails at startup with invalid type: string "true", expected a boolean. Relatedly, is_explicitly_disabled can no longer see enabled = "false", so that config becomes a parse error instead of a clean disable — loud failure is arguably the better outcome, but it should be an intentional, documented one. Unreleased → Changed already documents an equivalent bid_param_zone_overrides breaking change; please add a sibling entry telling operators to audit quoted scalars in [integrations.*].

❓ question

• Four legacy-env tests still assert behavior production does not have (settings.rs:2032 — details inline).

Non-blocking

♻️ refactor

• Regression test stops one layer short of the defect (settings.rs:3200 — details inline).

🤔 thinking

• PR description understates the scope: the title and body read as Prebid-only, but the behavior change spans every integration's config and every non-test load path. Worth stating so reviewers and operators reading the merge commit understand the blast radius.

📌 out of scope

• Docs still advertise integration env-var overrides, including forms EdgeZero rejects: docs/guide/integrations-overview.md:293-308, docs/guide/error-reference.md:117-123, and trusted-server.example.toml:163 (TRUSTED_SERVER__CREATIVE_OPPORTUNITIES__SLOT='[{…}]' — an array override the overlay refuses). These were already inaccurate before this PR, but removing the equivalent Prebid examples here makes the inconsistency conspicuous. Worth a follow-up issue.

⛏ nitpick

• normalize_legacy_env lost its doc comment and the val → value rename is diff noise (settings.rs:213 — details inline).

👍 praise

• Fixed at the source instead of special-casing Prebid — deleting the blanket coercion rather than adding a string-preserving exception for bid_param_overrides removes a whole class of silent retyping.
• The new test is a genuine regression test (settings.rs:3200) — cherry-picked onto main it fails with left: Number(12345), right: String("12345"), and it covers bid_param_zone_overrides and bid_param_override_rules in addition to the two shapes named in the PR body.

CI Status

All 19 GitHub checks pass (fmt, clippy, cargo test across fastly/axum/cloudflare/spin/CLI, cross-adapter parity, integration tests, vitest, CodeQL).

Independently reproduced locally against a worktree of the head commit:

• cargo fmt --all -- --check: PASS
• cargo clippy-axum: PASS
• cargo test -p trusted-server-core: PASS (1647 passed, 0 failed; main baseline 1648)
• cargo test-axum: PASS

[aram356]

❓ question — Why keep the four legacy-env tests that still depend on this coercion?

This PR deletes the two Prebid JSON-env tests, but leaves four tests that are now the only consumers of normalize_env_value / normalize_legacy_env:

• test_env_var_roundtrip_normalizes_integration_types (settings.rs:4222)
• test_integration_settings_from_env (settings.rs:3995)
• test_datadome_protection_scope_overrides_with_json_env (settings.rs:3249)
• test_datadome_protection_scope_overrides_with_indexed_env (settings.rs:3340)

I verified this by deleting the call on this line and running cargo test -p trusted-server-core: exactly those 4 fail, the other 1643 pass.

Two reasons they look stale rather than load-bearing:

1. test_env_var_roundtrip_normalizes_integration_types is documented as testing "the full build.rs round-trip … env vars are baked into Settings at build time via from_toml_and_env, serialized to TOML, then parsed back at runtime". There is no build.rs settings pipeline anymore — ts config push goes through EdgeZero's typed app-config loader.
2. test_datadome_protection_scope_overrides_with_json_env asserts a table can be replaced wholesale by a JSON env var. EdgeZero's apply_env_overlay coerces each env string into the existing TOML value's type and explicitly rejects array/table targets (env var … cannot override array / table values — env overlay supports scalar leaves only), which is exactly why removing the Prebid env doc examples in this PR is correct.

If those four are migrated to from_toml / from_json_value, then normalize_env_value, normalize_legacy_env, and from_toml_and_env can all be deleted outright — finishing what this PR started rather than leaving a #[cfg(test)] shim that keeps semantics alive which no production path has.

[aram356]

⛏ nitpick — The doc comment that normalize() carried was dropped in the rename. Since this is now a test-only shim, a one-liner explaining why it still exists would save the next reader a git blame:

/// Legacy test-only shim: expands JSON-encoded strings produced by the
/// `config` crate's `Environment` source. Production config never carries
/// untyped strings — `EdgeZero`'s env overlay coerces against the existing
/// TOML value's type — so this must not run on the runtime paths.
#[cfg(test)]
fn normalize_legacy_env(&mut self) {

Also, the val → value rename in normalize_env_value above adds a diff line without changing anything.

[aram356]

♻️ refactor — Good regression test (I confirmed it fails on main with left: Number(12345), right: String("12345")), but it stops one layer short of the reported defect.

It asserts on the raw integrations.get("prebid") JSON map. The bug in #932 is about the params actually sent to bidders, which are produced by the compiled rule engine — CompiledBidParamOverrideRule::from_bidder_override / from_zone_override in integrations/prebid.rs. A type regression introduced during rule compilation or the shallow merge would not be caught here.

Suggest extending the same test to also assert through the typed path:

let cfg = runtime_settings
    .integration_config::<PrebidIntegrationConfig>("prebid")
    .expect("Prebid config query should succeed")
    .expect("Prebid config should exist");
assert_eq!(
    cfg.bid_param_overrides["pubmatic"]["publisherId"],
    json!("12345"),
    "should preserve numeric-looking publisherId through the typed config"
);

and ideally one assertion on the merged params emitted by the compiled rules.

One more thing worth a comment in the test: the TOML -> Settings -> serde_json::to_value -> from_json_value chain it exercises is the production ts config push -> BlobEnvelope -> settings_from_config_blob path (config_payload.rs:39). Saying so makes it obvious this isn't a synthetic round-trip.