refactor(libutil/topo-sort): return variant instead of throwing#14479
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Ericson2314 merged 1 commit intoNixOS:masterfrom Nov 10, 2025
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refactor(libutil/topo-sort): return variant instead of throwing#14479Ericson2314 merged 1 commit intoNixOS:masterfrom
Ericson2314 merged 1 commit intoNixOS:masterfrom
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| auto orifu = get(outputReferencesIfUnregistered, name); | ||
| if (!orifu) | ||
| auto topoSortResult = topoSort(outputsToSort, {[&](const std::string & name) { | ||
| auto orifu = get(outputReferencesIfUnregistered, name); |
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Non-blocking: too complicated name. Refactor might improve that by moving to a smaller scope, but no concrete suggestions.
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(existing name it looks like)
| [&](const AlreadyRegistered &) { return StringSet{}; }, | ||
| [&](const PerhapsNeedToRegister & refs) { | ||
| StringSet referencedOutputs; | ||
| /* FIXME build inverted map up front so no quadratic waste here */ |
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The next PR has a fix for that :)
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tiny nits, then tiny unit test, then looks good!
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The variant has on the left-hand side the topologically sorted vector and the right-hand side is a pair showing the path and its parent that represent a cycle in the graph making the sort impossible. This change prepares for enhanced cycle error messages that can provide more context about the cycle. The variant approach allows callers to handle cycles more flexibly, enabling better error reporting that shows the full cycle path and which files are involved. Adapted from Lix commit f7871fc. Change-Id: I70a987f470437df8beb3b1cc203ff88701d0aa1b Co-Authored-By: Maximilian Bosch <maximilian@mbosch.me>
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Motivation
The variant has on the left-hand side the topologically sorted vector
and the right-hand side is a pair showing the path and its parent that
represent a cycle in the graph making the sort impossible.
This change prepares for enhanced cycle error messages that can provide
more context about the cycle. The variant approach allows callers to
handle cycles more flexibly, enabling better error reporting that shows
the full cycle path and which files are involved.
Adapted from Lix commit f7871fc.
Change-Id: I70a987f470437df8beb3b1cc203ff88701d0aa1b
Context
Taking another shot at #14218 with inspiration from how the Lix folks handled it :)
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