perf: use a custom trie for path conflict validation

[letFunny]

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[Copilot]

Pull request overview

Note

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Introduces a trie-based conflict detector for slice path collisions and expands tests to cover more glob/double-glob conflict cases.

Changes:

• Replaced the O(n²) glob/generate conflict scan in Release.validate() with a pathConflictTree-based detector.
• Added extensive regression tests for glob conflicts and new focused unit tests for the conflict tree/segmenter.
• Exposed internal conflict-tree types/helpers to external tests via export_test.go.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
internal/setup/setup.go	Switches validation to the new conflict-tree implementation.
internal/setup/conflict.go	Adds trie-based conflict detection and path segmentation logic.
internal/setup/setup_test.go	Adds multiple new test cases for glob/double-glob conflicts.
internal/setup/conflict_test.go	Adds unit tests for pathToSegments and the conflict tree structure.
internal/setup/export_test.go	Exports internal symbols to support setup_test package tests.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

[letFunny]

After some very light work on performance to improve the algorithm without added complexity (basically caching some data to avoid map lookups, iteration order, etc. *) the performance is:

Benchmark 1: BASE
  Time (mean ± σ):     14.511 s ±  0.071 s    [User: 15.039 s, System: 0.079 s]
  Range (min … max):   14.411 s … 14.617 s    10 runs
 
Benchmark 2: HEAD
  Time (mean ± σ):     151.2 ms ±   3.1 ms    [User: 181.2 ms, System: 18.6 ms]
  Range (min … max):   143.9 ms … 155.8 ms    19 runs
 
Summary
  'HEAD' ran
   95.96 ± 2.00 times faster than 'BASE'

*: All verified to reduce the number of cache misses using perf which is why the time also improves reliably.

[upils]

Thanks @letFunny ! I am amazed at how faster this is. I even looked at the messages we display to the user to see if we could remove any as this is now pretty much instantaneous.

The overall approach looks very sane. I could not find corner cases not handled properly. I have suggestions and questions but nothing that would change the approach.
This is definitely more complex than the previous implementation but the massive performance gains justify it I think.

[upils]

Thanks @letFunny. This is approved even though I think segmentEnd could be a bit more tweaked as suggested in the other comment. Feel free to move it to core review if you want to keep it like that or after this is fixed.

[lczyk]

Suggested change

	if path[0] != '/' {
	if path == "" || path[0] != '/' {

otherwise path[0] panics

[lczyk]

i guess the error message needs adjusting or there should be two checks with different error messages then

[lczyk]

aah! damn! sorry @letFunny / @upils i did not know the bot would do this. 😬 will do a comment and ping you in the future.

[upils]

@lczyk See https://github.com/canonical/chisel/pull/302/files#discussion_r3389540125 :D

[lczyk]

yep. the legitimate case i found was my own validation of this PR for which i wrote some fuzzers, and just directly called the fun. can be easily added if we ever add fuzzers here.

for reference, my fuzzers

all clean on 5m runs

[letFunny]

Ty for looking into this

[lczyk]

i did some fuzzing to validate this PR and all looks green on 5m run. +1 from me :)

for reference, my fuzzers

[lczyk]

@letFunny FYI found some more speed (and memory) letFunny#29. i promise i'm going to stop tinkering now. 😅