Suppress fabricated empty Prebid bidder params#910
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A configured bidder with no inline params and no matching override
expanded to `"bidder": {}`, which PBS rejects. After applying overrides,
drop fabricated empty bidders, preserve an explicitly supplied empty
object so genuine misconfiguration stays visible, and fall back to the
stored-request path when no eligible bidders remain.
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Review Summary
Approved with one non-blocking medium-severity finding documented inline. The primary fabricated-empty suppression, override ordering, and stored-request fallback behavior are covered by focused tests.
Please address the inline mixed-representation precedence case in follow-up work before relying on this path for clients that can send both direct bidder params and trustedServer.bidderParams.
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Summary
The fabricated-empty suppression, override ordering, stored-request fallback, and focused tests are otherwise sound, but mixed bidder representations can still recreate the invalid empty bidder object nondeterministically.
Blocking
🔧 wrench
- Mixed bidder representations have nondeterministic precedence: direct bidder params can be overwritten by a fabricated empty object depending on
HashMapiteration order (crates/trusted-server-core/src/integrations/prebid.rs:1440).
CI Status
- GitHub integration checks: PASS (4/4)
- fmt: PASS locally
- focused native core tests: PASS (44/44)
- Fastly test runtime: BLOCKED locally by unavailable macOS certificate keychain after successful compilation
- clippy-fastly: BLOCKED locally by a build-script tooling error (
Unrecognized option: 'p') - JS tests: not run; no JS/TS files changed
A slot can carry both a direct bidder entry with valid inline params and a
trustedServer entry whose bidderParams omits that bidder. Because slot.bidders
is a HashMap, the trustedServer expansion (which fabricates an empty {} for the
omitted bidder) could run after the direct entry and overwrite its valid params
via extend. The direct entry already marked the bidder explicit, so the empty
object survived the retention drop and PBS rejected the impression — the failure
this path is meant to eliminate — nondeterministically, depending on iteration
order.
Replace the extend with an entry().or_insert() loop so trustedServer-expanded
bidders only fill in absent entries and direct params win regardless of order.
Add a looped regression test exercising a slot with both representations.
…' into fix/prebid-suppress-empty-bidder-params
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Summary
Stacked on #899 (
feat/ssat-render-inline-creative) — base branch is that PR's head, notmain.A configured Prebid bidder with no inline params and no matching bid-param override was expanded into
"bidder": {}in the OpenRTB request. PBS rejects an empty bidder object, surfacing as the intermittent auction error.Fix
In
to_openrtb(crates/trusted-server-core/src/integrations/prebid.rs):{}).Behavior contract:
"bidder": {}).{}→ preserved (misconfiguration stays visible).The browser half of this defense (
prevBidderParamsretention on refresh) already shipped; this completes the server half.Tests
New unit tests in
prebid.rs:to_openrtb_drops_fabricated_empty_bidder_paramsto_openrtb_preserves_an_explicitly_empty_bidderto_openrtb_keeps_a_fabricated_bidder_that_an_override_populatesto_openrtb_falls_back_to_stored_request_when_all_bidders_are_fabricated_emptyVerification
cargo fmt --all -- --check✓cargo clippy-fastly✓cargo test-fastly✓ (1628 core + 99 fastly, 0 failed)Test plan
"bidder": {}to PBS