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QPLIST_E_DUPLICATE
The property list defines the same name more than once
QPLIST_E_DUPLICATE is the failure HRESULT 0x8004165C (-2147215780 signed; 2147751516 unsigned). Its severity bit is 1, facility is 4 (FACILITY_ITF), and code is 0x165C. AllStat describes it as “Duplicate property name.”
Contract and failing stage
This result belongs to legacy Windows property-list parsing and is returned while inserting a parsed property name after an earlier entry already claimed the normalized identity. The exact condition is: merged fragments, case folding, repeated includes or mutable generator state create equivalent or conflicting definitions. This stage matters because converting the result to a generic COM failure removes the information needed to choose the owner and retry policy.
This value belongs to the legacy property-list parser used to describe indexed properties and their types. Diagnose the external list as structured configuration: preserve line, column, token, type grammar and the property-list version instead of treating the file as arbitrary text. The exact public message comes from the legacy SDK contract; current property-system documentation does not replace the property-list grammar that rejected this file.
Conditions that produce it
- Retrying this result with the same all duplicate positions leaves the decisive contract violation intact.
- This result can appear when normalized name disagrees with the state expected while inserting a parsed property name after an earlier entry already claimed the normalized identity.
- a stale or transformed GUID and property ID can make the component observe that merged fragments, case folding, repeated includes or mutable generator state create equivalent or conflicting definitions.
- an incomplete type for each entry hides the distinction needed to separate this HRESULT from a later catalog or service failure.
- changes in source fragment between validation and execution can reproduce the result even when the user-visible input looks unchanged.
The strongest hypothesis for this HRESULT must account for the operation—inserting a parsed property name after an earlier entry already claimed the normalized identity—and the documented condition. Rejection of the property list does not yet distinguish file access, tokenization, type composition, GUID syntax or duplicate-definition failure.
Evidence to preserve
- use all duplicate positions to test whether the failure belongs to parsing, execution, indexing or capability negotiation.
- preserve normalized name before objects or work items are released.
- associate GUID and property ID with the exact UTC timestamp and correlation identifier.
- compare failing and known-good values for type for each entry under the same provider or handler version.
- record the source and normalization path of source fragment, not only its display form.
- use property-list file identity and hash to test whether the failure belongs to parsing, execution, indexing or capability negotiation.
Evidence for this HRESULT should reflect what the component actually received. Hash the complete file if it is sensitive while retaining encoding, line, column, raw token class and the surrounding property declaration.
Diagnostic sequence
- Capture all duplicate positions and normalized name at the call boundary that returns this result.
- confirm the operation reached inserting a parsed property name after an earlier entry already claimed the normalized identity with the intended GUID and property ID.
- perform the decisive check: collect every occurrence and compare GUID, property ID and type before deleting anything.
- reduce the case until changing type for each entry alone changes the HRESULT or proves it irrelevant.
- apply the recovery only after verifying source fragment; preserve the original result for comparison.
A useful control for this HRESULT changes one dimension at a time. Begin with a one-property list accepted by the same parser, then restore the failing declaration token by token while preserving encoding and line endings.
Recovery and retry
Keep one authoritative equivalent entry or fail deployment when the duplicate maps to different properties. Retry it only after the responsible input or state changes and the previous operation has completed or been cancelled. Delay cannot repair a deterministic file, token or type-grammar defect; retry only after the property list or its readable source changes.
What the code does not prove
It does not prove that every property definition is unusable or that reindexing is required; it identifies a property-list read or grammar boundary. Without code-specific evidence for this HRESULT, the value also cannot identify which wrapper, configuration, handler or service transition introduced the condition.
Related HRESULT values
QPLIST_S_DUPLICATE is the separate informational exact-duplicate result. Keep the symbolic HRESULT beside the stage name in telemetry because nearby constants may require different owners, user messages and retry rules despite the same visible symptom.
Developer and administrator guidance
Retain the property-list file hash, encoding, parser version, line and column, raw token and expected grammar production. Do not log credentials or unrestricted document content. Before replacing the whole property configuration for this HRESULT, validate a copied file and preserve the exact failing location.
Practical scenario
Two modules define `DocTitle`, but one uses a custom GUID. The merge tool rejects the conflicting duplicate instead of relying on file order. A regression test for this HRESULT should assert the decisive evidence, change only the responsible condition, and include one neighboring HRESULT so future code cannot collapse distinct failures into a generic message.
Official Microsoft references
- Microsoft: legacy Indexing Service error messages
- Microsoft: OLE DB provider for Indexing Service
- Microsoft: Windows Search SQL syntax
- Microsoft: HRESULT values
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