feat: add terminal node detection to Graph class

[Jkavia]

Part of POC to detect terminal nodes, adding a dead method block to be used in future work.

Summary by CodeRabbit

• New Features

  • Added terminal node identification capability for graph structures, enabling detection of vertices with no outgoing connections.

• Tests

  • Comprehensive test coverage added for terminal node detection across diverse scenarios including multi-branch graphs, isolated nodes, linear chains, and empty configurations.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

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Walkthrough

A new get_terminal_nodes() method is added to the Graph class that returns IDs of vertices with no outgoing edges by querying the existing successor_map. Four unit tests cover scenarios including multi-branch graphs, single nodes, linear chains, and empty graphs.

Changes

Cohort / File(s)	Summary
Implementation src/lfx/src/lfx/graph/graph/base.py	Adds get_terminal_nodes(self) -> list[str] method to Graph class; returns terminal vertex IDs by filtering vertices with empty successor entries
Unit Tests src/lfx/tests/unit/graph/graph/test_base.py	Adds four test cases: test_get_terminal_nodes() (multi-branch graph), test_get_terminal_nodes_single_node() (isolated node), test_get_terminal_nodes_linear_chain() (linear chain), test_get_terminal_nodes_empty_graph() (empty graph)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

• The implementation is a straightforward read-only query helper with no complex logic or side effects
• Test coverage is comprehensive and follows consistent patterns
• Changes are localized to a single method addition and its corresponding test suite

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 77.78% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (6 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Test Coverage For New Implementations	✅ Passed	The PR includes comprehensive test coverage for the new get_terminal_nodes() functionality with four unit tests covering multi-branch graphs, single nodes, linear chains, and empty graphs.
Test Quality And Coverage	✅ Passed	The pull request includes four well-structured pytest test functions that comprehensively cover get_terminal_nodes() functionality across diverse scenarios including multi-branch graphs, edge cases, linear chains, and empty graphs with proper initialization and meaningful assertions.
Test File Naming And Structure	✅ Passed	The test file fully adheres to all specified test naming and structure requirements, with comprehensive edge case coverage and proper assertions.
Excessive Mock Usage Warning	✅ Passed	The tests for get_terminal_nodes() demonstrate excellent test design with minimal mock usage, using real Graph and component objects to verify genuine functionality.
Title check	✅ Passed	The title accurately describes the main change: adding a new get_terminal_nodes() method to the Graph class for detecting terminal nodes with no outgoing edges.

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[dkaushik94]

Looks good!

[edwinjosechittilappilly]

@coderabbitai what are your thoughts on this?
How is the parallel graphs tackled?

[coderabbitai]

@edwinjosechittilappilly Great question! The implementation looks solid and handles parallel graphs naturally. Here's my analysis:

Implementation Thoughts

The get_terminal_nodes() method uses a straightforward approach by checking the successor_map to identify vertices with no outgoing edges. This is both efficient and correct since the successor_map is already maintained by the graph structure.

Handling Parallel Graphs

For parallel graphs (multiple independent branches executing concurrently), this implementation handles them elegantly:

Example scenario:

Input -> Branch A -> Terminal A
      -> Branch B -> Terminal B
      -> Branch C -> Terminal C

The method will return all terminal nodes: [Terminal A, Terminal B, Terminal C]. This is the correct behavior because:

1. No special handling needed - The method doesn't distinguish between serial vs. parallel paths; it simply identifies all vertices without successors
2. Natural coverage - Multiple disconnected branches each get their terminal nodes included
3. Useful for downstream logic - Returning all terminals allows callers to determine when the entire graph (including all parallel branches) has completed execution

Potential Considerations

1. Isolated nodes - A single vertex with no edges is correctly identified as terminal (covered in your tests)
2. Cyclic graphs - Vertices in cycles won't be terminal unless they have no edges leaving the cycle
3. Empty graph - Returns empty list (correct behavior)

The implementation is clean and leverages existing graph infrastructure well. For a POC, this is a solid foundation for terminal-node detection work!

[github-actions]

Frontend Unit Test Coverage Report

Coverage Summary

Lines	Statements	Branches	Functions
	16.42% (4606/28041)	9.73% (2106/21644)	10.76% (664/6166)

Unit Test Results

Tests	Skipped	Failures	Errors	Time
1803	0 💤	0 ❌	0 🔥	24.837s ⏱️

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.95%. Comparing base (397deff) to head (b9c4be6).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10789      +/-   ##
==========================================
- Coverage   32.96%   32.95%   -0.01%     
==========================================
  Files        1387     1387              
  Lines       65385    65387       +2     
  Branches     9680     9680              
==========================================
- Hits        21551    21547       -4     
- Misses      42736    42742       +6     
  Partials     1098     1098              

Flag	Coverage Δ
backend	52.18% <ø> (-0.04%)	⬇️
frontend	15.16% <ø> (ø)
lfx	39.27% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/lfx/src/lfx/graph/graph/base.py	48.48% <100.00%> (+0.08%)	⬆️

... and 3 files with indirect coverage changes

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[ogabrielluiz]

LGTM

[Jkavia]

@coderabbitai generate docstrings

[coderabbitai]

✅ Actions performed

Initiated docstring generation; will generate only if new commits exist.

[coderabbitai]

Note

Docstrings generation - SUCCESS
Generated docstrings for this pull request at #10974

[edwinjosechittilappilly]

LGTM