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BrianHotoppandClaude Opus 4.7
3eeac9deae
Fixes #6886. dependencyTree, dependencyBrowseTree, and inspect tree re-explore the same node once per incoming edge. In a DAG with N levels and M children per node the rendered output is O(M^N) -- the OP needed >16 GB heap, #7360 has a 6 GB heap dump, and Friendseeker's analysis on the issue showed the exponential re-traversal directly. Fix: track a visited set across the renderer's recursion. The first time a node is encountered it is rendered in full; on subsequent visits the entry collapses to a one-line +- <id> (*) (ASCII) or a <id> (*) leaf (JSON), matching Maven's dependency:tree (*) convention. Cycle detection (separate parents set, (cycle) marker) is unchanged. Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>
67 lines
2.2 KiB
Markdown
67 lines
2.2 KiB
Markdown
## Dependency tree: duplicate-subtree collapse
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`dependencyTree`, `dependencyBrowseTree`, and `inspect tree` now collapse
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duplicate subtrees in a DAG to a single line marked `(*)`, matching the
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convention used by Maven's `dependency:tree`. The first occurrence is
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rendered in full; subsequent occurrences appear as `+- <id> (*)`.
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This fixes [#6886][i6886]: rendering a deep diamond DAG no longer
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produces `O(M^N)` output (and the OOMs that came with it).
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### Output change
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Before:
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```
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o:root_2.13:0.1
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+-o:subA_2.13:0.1 [S]
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| +-o:common_2.13:0.1 [S]
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| | +-org.scala-lang:scala-library:2.13.16 [S]
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| +-org.scala-lang:scala-library:2.13.16 [S]
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+-o:subB_2.13:0.1 [S]
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| +-o:common_2.13:0.1 [S] # full subtree again
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| | +-org.scala-lang:scala-library:2.13.16 [S]
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| +-org.scala-lang:scala-library:2.13.16 [S]
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+-org.scala-lang:scala-library:2.13.16 [S]
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```
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After:
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```
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o:root_2.13:0.1
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+-o:subA_2.13:0.1 [S]
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| +-o:common_2.13:0.1 [S]
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| | +-org.scala-lang:scala-library:2.13.16 [S]
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| +-org.scala-lang:scala-library:2.13.16 [S]
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+-o:subB_2.13:0.1 [S]
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| +-o:common_2.13:0.1 [S] (*) # collapsed
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| +-org.scala-lang:scala-library:2.13.16 [S] (*)
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+-org.scala-lang:scala-library:2.13.16 [S] (*)
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```
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### Affected surfaces
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- `dependencyTree`: ASCII output (also `dependencyTreeList`,
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`dependencyTreeStats`).
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- `dependencyBrowseTree`: JSON / HTML view.
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- `inspect tree`: the setting-graph renderer is the same code path, so
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the `(*)` marker shows up there too. Most users don't think of
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`inspect tree` as "the dependency tree" -- this note is the
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heads-up.
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### Contract for tooling consumers
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A line whose entry ends with `(*)` is a reference to the canonical
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(first-rendered) occurrence of that node within the same render.
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Tools parsing `dependencyTree` / `dependencyBrowseTree` output should
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treat `<id> (*)` as a back-pointer rather than a distinct dependency.
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### Scope
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Dedup is currently within a single root's subtree. Cross-root dedup
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(when a `ModuleGraph` has multiple roots that share a transitive
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closure) is tracked separately as [#9227][i9227].
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[i6886]: https://github.com/sbt/sbt/issues/6886
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[i9227]: https://github.com/sbt/sbt/issues/9227
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