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fix(uv): tree --invert silently drops leaf cycles #3

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f6a47db
fix(uv): tree --invert now handles leaf cycles without silently dropp…
Jul 8, 2026
d856a5f
test: add invert_leaf_cycle integration test for tree --invert with l…
Jul 8, 2026
a64c71e
fmt: collapse .child().write_str() chain in invert_leaf_cycle test
Jul 8, 2026
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34 changes: 31 additions & 3 deletions crates/uv-resolver/src/lock/tree.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ use std::fmt::Write;
use either::Either;
use itertools::Itertools;
use owo_colors::OwoColorize;
use petgraph::algo::tarjan_scc;
use petgraph::graph::{EdgeIndex, NodeIndex};
use petgraph::prelude::EdgeRef;
use petgraph::{Direction, Graph};
Expand Down Expand Up @@ -436,16 +437,43 @@ impl<'env> TreeDisplay<'env> {
} else {
let mut roots = if invert {
// For inverted trees, find leaf packages (nodes with no incoming
// edges).
graph
// edges after reversal).
let mut roots: Vec<_> = graph
.node_indices()
.filter(|index| {
graph
.edges_directed(*index, Direction::Incoming)
.next()
.is_none()
})
.collect::<Vec<_>>()
.collect();

// If no node has zero incoming edges (e.g., a leaf cycle), fall
// back to treating each root SCC as a root. A root SCC is one
// whose nodes have no incoming edges from outside the SCC.
if roots.is_empty() {
let sccs = tarjan_scc(&graph);
for scc in &sccs {
let has_external_incoming = scc.iter().any(|node| {
graph
.edges_directed(*node, Direction::Incoming)
.any(|edge| !scc.contains(&edge.source()))
});
if !has_external_incoming {
// Pick the best node in the SCC as root: prefer
// packages over Root nodes.
let root = scc
.iter()
.find(|n| matches!(graph[**n], Node::Package(_)))
.or_else(|| scc.first());
if let Some(root) = root {
roots.push(*root);
}
}
}
}
Comment on lines +451 to +474

@coderabbitai coderabbitai Bot Jul 8, 2026

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🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

🧩 Analysis chain

🏁 Script executed:

sed -n '1,260p' crates/uv-resolver/src/lock/tree.rs

Repository: beast-ofcourse/uv

Length of output: 10717

🏁 Script executed:

rg -n "tarjan_scc|roots\.is_empty\(|render\(|leaf cycle|SCC|zero incoming|incoming edges" crates/uv-resolver/src/lock/tree.rs crates/uv-resolver/src -g '!target'

Repository: beast-ofcourse/uv

Length of output: 2059

🏁 Script executed:

fd -a -t f crates/uv-resolver/src/lock

Repository: beast-ofcourse/uv

Length of output: 569

🏁 Script executed:

#!/bin/bash
set -euo pipefail

echo '--- tree.rs outline ---'
ast-grep outline crates/uv-resolver/src/lock/tree.rs --view expanded || true

echo '--- relevant lines ---'
nl -ba crates/uv-resolver/src/lock/tree.rs | sed -n '380,520p'

echo '--- tests and references ---'
rg -n "tree::|render\(|tarjan_scc|leaf cycle|roots\.is_empty\(|source SCC|zero incoming" crates/uv-resolver/src -g '!target'

Repository: beast-ofcourse/uv

Length of output: 2372

🏁 Script executed:

#!/bin/bash
set -euo pipefail

echo '--- surrounding code ---'
nl -ba crates/uv-resolver/src/lock/tree.rs | sed -n '420,500p'

echo '--- search for tests covering mixed graphs / leaf cycles ---'
rg -n "leaf cycle|cycle.*leaf|mixed graph|source SCC|tarjan_scc|roots\.is_empty\(|zero incoming" crates/uv-resolver -g '!target' -g '*.rs'

Repository: beast-ofcourse/uv

Length of output: 220

🏁 Script executed:

#!/bin/bash
set -euo pipefail

python3 - <<'PY'
from pathlib import Path
import re

path = Path('crates/uv-resolver/src/lock/tree.rs')
text = path.read_text()

# Extract the root-selection block for inspection
m = re.search(r'let mut roots: Vec<_> = graph.*?roots\s*$', text, re.S | re.M)
print('found_block=', bool(m))
print('contains_roots_is_empty=', 'roots.is_empty()' in text)
print('contains_tarjan_scc=', 'tarjan_scc(&graph)' in text)
print('contains_scc_contains=', '.contains(&edge.source())' in text)
PY

Repository: beast-ofcourse/uv

Length of output: 257

🏁 Script executed:

python3 - <<'PY'
from pathlib import Path

path = Path('crates/uv-resolver/src/lock/tree.rs')
lines = path.read_text().splitlines()

for start, end, label in [
    (420, 490, 'root selection'),
    (700, 760, 'render'),
    (920, 1030, 'fmt + tests tail'),
]:
    print(f'\n--- {label} ({start}-{end}) ---')
    for i in range(start-1, min(end, len(lines))):
        print(f'{i+1:4d}: {lines[i]}')
PY

Repository: beast-ofcourse/uv

Length of output: 6839

🏁 Script executed:

python3 - <<'PY'
from pathlib import Path
import re

path = Path('crates/uv-resolver/src/lock/tree.rs')
lines = path.read_text().splitlines()

print('--- test function names in tree.rs ---')
for i, line in enumerate(lines, 1):
    if re.match(r'\s*fn\s+test_|^\s*#\[test\]', line):
        print(f'{i}: {line}')

print('\n--- occurrences of render() in tests section ---')
for i, line in enumerate(lines, 1):
    if 'render()' in line or 'TreeDisplay::new' in line:
        print(f'{i}: {line}')
PY

Repository: beast-ofcourse/uv

Length of output: 285

🏁 Script executed:

python3 - <<'PY'
from pathlib import Path

lines = Path('crates/uv-resolver/src/lock/tree.rs').read_text().splitlines()

for start, end in [(420, 490), (700, 760), (980, 1120)]:
    print(f'\n--- lines {start}-{end} ---')
    for i in range(start-1, min(end, len(lines))):
        print(f'{i+1:4d}: {lines[i]}')
PY

Repository: beast-ofcourse/uv

Length of output: 6182

🏁 Script executed:

python3 - <<'PY'
from pathlib import Path
import re

lines = Path('crates/uv-resolver/src/lock/tree.rs').read_text().splitlines()

# Print the root-selection block and render() implementation.
for start, end, label in [
    (435, 490, 'root-selection block'),
    (707, 760, 'render'),
    (1000, 1180, 'tests/nearby examples'),
]:
    print(f'\n--- {label} ({start}-{end}) ---')
    for i in range(start-1, min(end, len(lines))):
        print(f'{i+1:4d}: {lines[i]}')

print('\n--- test markers in file ---')
for i, line in enumerate(lines, 1):
    if '#[test]' in line:
        print(f'{i}: {line}')
PY

Repository: beast-ofcourse/uv

Length of output: 5408

🏁 Script executed:

python3 - <<'PY'
from pathlib import Path
import re

text = Path('crates/uv-resolver/src/lock/tree.rs').read_text()

# Look for tests or fixtures exercising rendering of disconnected / cyclic graphs.
patterns = [
    r'leaf cycle',
    r'mixed graph',
    r'roots\.is_empty\(',
    r'tarjan_scc',
    r'Render',
    r'TreeDisplay::new\(',
]
for pat in patterns:
    print(f'\n--- matches for {pat!r} ---')
    for m in re.finditer(pat, text):
        line = text.count('\n', 0, m.start()) + 1
        print(line)
PY

Repository: beast-ofcourse/uv

Length of output: 388

Treat every source SCC as a root in invert mode
roots.is_empty() skips the SCC fallback as soon as any zero-incoming node exists, so a separate leaf-cycle component in a mixed graph never becomes a root and render() drops it. Merge the source-SCC pass into the initial root selection and add a mixed acyclic + leaf-cycle test.

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/uv-resolver/src/lock/tree.rs` around lines 451 - 474, The root
selection logic in tree.rs currently only runs the SCC fallback when roots is
empty, so a graph with any zero-incoming node can still skip a separate source
SCC like a leaf cycle. Update the root discovery in the invert-mode path around
tarjan_scc/roots so every SCC with no external incoming edges is added as a root
regardless of whether other roots already exist, and keep the package-over-Root
preference when choosing the representative node. Add a mixed acyclic plus
leaf-cycle test covering render() to verify the cycle component is not dropped.


roots
} else {
// For non-inverted trees, use the root node directly.
graph
Expand Down
86 changes: 86 additions & 0 deletions crates/uv/tests/project/tree.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2998,3 +2998,89 @@ fn workspace_circular_dependencies() -> Result<()> {

Ok(())
}

#[test]
fn invert_leaf_cycle() -> Result<()> {
let context = uv_test::test_context!("3.12");

// Create a lockfile with a leaf cycle: bar ↔ baz form a cycle where no
// node in the reversed graph has zero incoming edges. Without the SCC
// fallback, `--invert` would produce no output.
context
.temp_dir
.child("pyproject.toml")
.write_str(indoc! {r#"
[project]
name = "foo"
version = "1.0.0"
requires-python = ">=3.12"
dependencies = ["bar==1.0.0"]
"#})?;

context.temp_dir.child("uv.lock").write_str(indoc! {r#"
version = 1
revision = 3
requires-python = ">=3.12"
[[package]]
name = "foo"
version = "1.0.0"
source = { virtual = "." }
dependencies = [
{ name = "bar" },
]
[[package]]
name = "bar"
version = "1.0.0"
source = { registry = "https://pypi.org/simple" }
dependencies = [
{ name = "baz" },
]
[[package]]
name = "baz"
version = "1.0.0"
source = { registry = "https://pypi.org/simple" }
dependencies = [
{ name = "bar" },
]
"#})?;

// Normal tree — no issue; the cycle is displayed as usual.
uv_snapshot!(context.filters(), context.tree().arg("--frozen"), @r"
success: true
exit_code: 0
----- stdout -----
foo v1.0.0
└── bar v1.0.0
└── baz v1.0.0
└── bar v1.0.0 (*)
(*) Package tree already displayed
----- stderr -----
"
);

// Inverted tree — without the SCC fallback every node in the reversed
// graph has incoming edges, yielding an empty root set and no output.
// With the fix, the SCC {bar, baz} is detected as a root SCC.
uv_snapshot!(context.filters(), context.tree().arg("--frozen").arg("--invert"), @r"
success: true
exit_code: 0
----- stdout -----
bar v1.0.0
├── baz v1.0.0
│ └── bar v1.0.0 (*)
└── foo v1.0.0
(*) Package tree already displayed
----- stderr -----
"
);

Ok(())
}
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