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C API: Add copy_path to Store API #14768

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Merged
xokdvium merged 1 commit into from
Feb 10, 2026
Merged

C API: Add copy_path to Store API #14768

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1 change: 1 addition & 0 deletions doc/manual/rl-next/c-api-new-store-methods.md
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Original file line number Diff line number Diff line change
Expand Up @@ -6,3 +6,4 @@ prs: [14766]
The C API now includes additional methods:

- `nix_store_query_path_from_hash_part()` - Get the full store path given its hash part
- `nix_store_copy_path()` - Copy a single store path between two stores, allows repairs and configuring signature checking
22 changes: 22 additions & 0 deletions src/libstore-c/nix_api_store.cc
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Expand Up @@ -352,4 +352,26 @@ StorePath * nix_store_query_path_from_hash_part(nix_c_context * context, Store *
NIXC_CATCH_ERRS_NULL
}

nix_err nix_store_copy_path(
nix_c_context * context, Store * srcStore, Store * dstStore, const StorePath * path, bool repair, bool checkSigs)
{
if (context)
context->last_err_code = NIX_OK;
try {
if (srcStore == nullptr)
return nix_set_err_msg(context, NIX_ERR_UNKNOWN, "Source store is null");
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@xokdvium xokdvium Feb 6, 2026 •
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I wonder if we should add a new error type like NIX_ERR_INVALID_ARGUMENT for such cases.

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@pkpbynum pkpbynum Feb 6, 2026

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I'm just following the existing usage here: https://github.com/NixOS/nix/blob/master/src/libmain-c/nix_api_main.cc#L26

Could we save that sort of change for follow-up? It seems like it would/should involve a wider cleanup of error handling in C API:

  1. Improve error types/messages
  2. check inputs for nullptr

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@Ericson2314 Ericson2314 Feb 9, 2026

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Frankly I wouldn't mind if this was just an assert, or not here at all, since both arguments being non-null are morally part of the signature.

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@xokdvium xokdvium Feb 9, 2026

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We can address this in a follow-up I suppose. The current state of things where stuff just segfaults isn't ideal and certainly not the long-term goal. Adding an error code does pose a backwards-compatibility issue and the current set of error codes isn't particularly extensible and the error codes aren't yet documented.

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@pkpbynum pkpbynum Feb 10, 2026

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Are there any additional changes I should make, or is this good to merge as-is?

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@xokdvium xokdvium Feb 10, 2026

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I think @roberth has made a comment about having some tests for this, but maybe this can be done in a follow-up.


if (dstStore == nullptr)
return nix_set_err_msg(context, NIX_ERR_UNKNOWN, "Destination store is null");

if (path == nullptr)
return nix_set_err_msg(context, NIX_ERR_UNKNOWN, "Store path is null");

auto repairFlag = repair ? nix::RepairFlag::Repair : nix::RepairFlag::NoRepair;
auto checkSigsFlag = checkSigs ? nix::CheckSigsFlag::CheckSigs : nix::CheckSigsFlag::NoCheckSigs;
nix::copyStorePath(*srcStore->ptr, *dstStore->ptr, path->path, repairFlag, checkSigsFlag);
}
NIXC_CATCH_ERRS
}

} // extern "C"
13 changes: 13 additions & 0 deletions src/libstore-c/nix_api_store.h
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Expand Up @@ -270,6 +270,19 @@ nix_derivation * nix_store_drv_from_store_path(nix_c_context * context, Store *
*/
StorePath * nix_store_query_path_from_hash_part(nix_c_context * context, Store * store, const char * hash);

/**
* @brief Copy a path from one store to another.
*
* @param[out] context Optional, stores error information
* @param[in] srcStore nix source store reference
* @param[in] dstStore nix destination store reference
* @param[in] path The path to copy
* @param[in] repair Whether to repair the path
* @param[in] checkSigs Whether to check path signatures are trusted before copying
*/
nix_err nix_store_copy_path(
nix_c_context * context, Store * srcStore, Store * dstStore, const StorePath * path, bool repair, bool checkSigs);

// cffi end
#ifdef __cplusplus
}
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