feat(slurm): default to flat YAML topology if partition topology is absent

[dmitsh]

No description provided.

[greptile-apps]

Greptile Summary

This PR updates the Slurm YAML topology generation logic so that when a partition's node list cannot be resolved to any valid topology data (e.g., all nodes are offline or absent from the topology graph), the output defaults to a flat: true topology unit instead of emitting an empty tree or block structure. The change affects both getTreeTopologyUnit (checks len(tree) == 0 after calling getPartitionTree) and getBlockTopologyUnit (checks len(blockMap) == 0 after iterating resolved nodes), and is covered by a new test TestEmptyPartitionTopology.

• getBlockTopologyUnit: when no nodes from the partition spec can be mapped to block data, tu.Flat = true is set rather than returning an empty BlockTopo.
• getTreeTopologyUnit: when getPartitionTree returns an empty map (no resolvable node paths), tu.Flat = true is set rather than returning an empty TreeTopo.
• The Tree and Block fields on TopologyUnit are now only populated inside their respective else branches, meaning neither field will be nil-but-empty in the flat-fallback path.
• A new test exercises all five combinations: valid tree, down-node tree, mixed-valid block, down-node block, and explicit flat — verifying the expected YAML output for each.

Confidence Score: 5/5

• This PR is safe to merge — the fallback logic is simple, well-isolated, and fully exercised by the new test.
• The change is small and localised to two functions in yaml.go. The existing Flat field on TopologyUnit was already supported (used by TopologyFlat plugin), so no new struct changes are needed. The new TestEmptyPartitionTopology test directly validates both the tree and block fallback paths. No regressions to existing tests are expected, and the prior behaviour (empty switch/block lists) was arguably misleading to Slurm.
• No files require special attention.

Important Files Changed

Filename	Overview
pkg/translate/yaml.go	Refactors getBlockTopologyUnit and getTreeTopologyUnit to fall back to a flat topology (tu.Flat = true) when no valid partition nodes are found, instead of emitting an empty block/tree structure. Logic is correct; the nBlocks variable in the if-initializer is slightly verbose but valid.
pkg/translate/yaml_test.go	Adds TestEmptyPartitionTopology covering tree and block topologies with no resolvable nodes, verifying they produce flat: true, alongside existing valid topologies. Good coverage of the new fallback behaviour.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[getTreeTopologyUnit / getBlockTopologyUnit] --> B{Gather candidate\nnodes from spec}
    B --> C{Any valid nodes\nresolved?}
    C -- "No valid nodes\n(all 'down' / not found)" --> D[Build empty\ntree / blockMap]
    C -- "Some valid nodes" --> E[Build partition tree\nor block map]
    D --> F{len == 0?}
    E --> F
    F -- Yes --> G[tu.Flat = true\nReturn flat TopologyUnit]
    F -- No --> H{Plugin type}
    H -- Tree --> I[Traverse tree,\npopulate Switches]
    H -- Block --> J[Sort blocks,\npopulate Blocks]
    I --> K[Return TreeTopo TopologyUnit]
    J --> L[Return BlockTopo TopologyUnit]
    G --> M[YAML: flat: true]
    K --> N[YAML: tree: switches: ...]
    L --> O[YAML: block: blocks: ...]

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_{Last reviewed commit: 15e11ac}

[codecov]

Codecov Report

❌ Patch coverage is 96.07843% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.98%. Comparing base (d79be88) to head (15e11ac).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/translate/yaml.go	96.07%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #235      +/-   ##
==========================================
+ Coverage   66.96%   66.98%   +0.02%     
==========================================
  Files          82       82              
  Lines        4646     4649       +3     
==========================================
+ Hits         3111     3114       +3     
  Misses       1424     1424              
  Partials      111      111              

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