libstore: structured diagnostics for local build rejection#15266
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Ericson2314 merged 1 commit intoNixOS:masterfrom Feb 17, 2026
Merged
libstore: structured diagnostics for local build rejection#15266Ericson2314 merged 1 commit intoNixOS:masterfrom
Ericson2314 merged 1 commit intoNixOS:masterfrom
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When `max-jobs = 0` and no remote builders are available, Nix reported "required system or feature not available" even though the system and features matched fine. The `canBuildLocally` lambda returned a plain `bool`, conflating a configuration knob (`max-jobs = 0`) with actual incompatibility (wrong platform, missing features). It also short-circuited on the first failing check, so a user with both a platform mismatch and missing features would only see one of the two. This commit replaces the bool with a `LocalBuildRejection` struct whose `WrongLocalStore` variant collects all applicable failures into `badPlatform`, `missingFeatures`, and an orthogonal `maxJobsZero` flag. Platform mismatch and missing features now produce separate error paragraphs, and all applicable reasons appear in a single message. The local-build capability check also now returns `std::variant<LocalBuildCapability, LocalBuildRejection>`, bundling the `LocalStore &` and optional `ExternalBuilder *` together.
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Motivation
When
max-jobs = 0and no remote builders are available, Nix reported"required system or feature not available" even though the system and
features matched fine. The
canBuildLocallylambda returned a plainbool, conflating a configuration knob (max-jobs = 0) with actualincompatibility (wrong platform, missing features). It also short-circuited
on the first failing check, so a user with both a platform mismatch and
missing features would only see one of the two.
This commit replaces the bool with a
LocalBuildRejectionstruct whoseWrongLocalStorevariant collects all applicable failures intobadPlatform,missingFeatures, and an orthogonalmaxJobsZeroflag.Platform mismatch and missing features now produce separate error
paragraphs, and all applicable reasons appear in a single message.
The local-build capability check also now returns
std::variant<LocalBuildCapability, LocalBuildRejection>, bundlingthe
LocalStore &and optionalExternalBuilder *together.Context
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